A proposed clinical classification for pituitary neoplasms to guide therapy and prognosis

No comprehensive classification system that guides prognosis and therapy of pituitary adenomas exists. The 2022 WHO histopathology-based classification system can only be applied to lesions that are resected, which represent few clinically significant pituitary adenomas. Many factors independent of histopathology provide mechanistic insight into causation and influence prognosis and treatment of pituitary adenomas. We propose a new approach to guide prognosis and therapy of pituitary adenomas by integrating clinical, genetic, biochemical, radiological, pathological, and molecular information for all adenomas arising from anterior pituitary cell lineages. The system uses an evidence-based scoring of risk factors to yield a cumulative score that reflects disease severity and can be used at the bedside to guide pituitary adenoma management. Once validated in prospective studies, this simple manageable classification system could provide a standardised platform for assessing disease severity, prognosis, and effects of therapy on pituitary adenomas.

Metabolic control of puberty: 60 years in the footsteps of Kennedy and Mitra's seminal work

An individual's nutritional status has a powerful effect on sexual maturation. Puberty onset is delayed in response to chronic energy insufficiency and is advanced under energy abundance. The consequences of altered pubertal timing for human health are profound. Late puberty increases the chances of cardiometabolic, musculoskeletal and neurocognitive disorders, whereas early puberty is associated with increased risks of adult obesity, type 2 diabetes mellitus, cardiovascular diseases and various cancers, such as breast, endometrial and prostate cancer. Kennedy and Mitra's trailblazing studies, published in 1963 and using experimental models, were the first to demonstrate that nutrition is a key factor in puberty onset. Building on this work, the field has advanced substantially in the past decade, which is largely due to the impressive development of molecular tools for experimentation and population genetics. In this Review, we discuss the latest advances in basic and translational sciences underlying the nutritional and metabolic control of pubertal development, with a focus on perspectives and future directions.

Sex differences in muscle health in simulated micro- and partial-gravity environments in rats

Skeletal muscle size and strength are important for overall health for astronauts. However, how male and female muscle may respond differently to micro- and partial-gravity environments is not fully understood. The purpose of this study was to determine how biological sex and sex steroid hormones influence the progression of muscle atrophy after long term exposure to micro and partial gravity environments in male and female rats. Male and female Fisher rats (n ​= ​120) underwent either castration/ovariectomy or sham surgeries. After two weeks recovery, animals were divided into microgravity (0g), partial-gravity (40% of weight bearing, 0.4g), or full weight bearing (1g) interventions for 28 days. Measurements of muscle size and strength were evaluated prior to and after interventions. At 0g, females lost more dorsiflexion strength, plantar flexion strength, and other metrics of muscle size compared to males; castration/ovariectomy did not influence these differences. Additionally, at 0.4g, females lost more dorsiflexion strength, plantar flexion strength, and other metrics of muscle strength compared to males; castration/ovariectomy did not influence these differences. Females have greater musculoskeletal aberrations during exposure to both microgravity and partial-gravity environments; these differences are not dependent on the presence of sex steroid hormones. Correspondingly, additional interventions may be necessary to mitigate musculoskeletal loss in female astronauts to protect occupational and overall health.

OSR1 disruption contributes to uterine factor infertility via impaired Müllerian duct development and endometrial receptivity

Three sisters, born from consanguineous parents, manifested a unique Müllerian anomaly characterized by uterine hypoplasia with thin estrogen-unresponsive endometrium and primary amenorrhea, but with spontaneous tubal pregnancies. Through whole-exome sequencing followed by comprehensive genetic analysis, a missense variant was identified in the OSR1 gene. We therefore investigated OSR1/OSR1 expression in postpubertal human uteri, and the prenatal and postnatal expression pattern of Osr1/Osr1 in murine developing Müllerian ducts (MDs) and endometrium, respectively. We then investigated whether Osr1 deletion would affect MD development, using WT and genetically engineered mice. Human uterine OSR1/OSR1 expression was found primarily in the endometrium. Mouse Osr1 was expressed prenatally in MDs and Wolffian ducts (WDs), from rostral to caudal segments, in E13.5 embryos. MDs and WDs were absent on the left side and MDs were rostrally truncated on the right side of E13.5 Osr1-/- embryos. Postnatally, Osr1 was expressed in mouse uteri throughout their lifespan, peaking at postnatal days 14 and 28. Osr1 protein was present primarily in uterine luminal and glandular epithelial cells and in the epithelial cells of mouse oviducts. Through this translational approach, we demonstrated that OSR1 in humans and mice is important for MD development and endometrial receptivity and may be implicated in uterine factor infertility.

Diagnosis and management of prolactin-secreting pituitary adenomas: a Pituitary Society international Consensus Statement

This Consensus Statement from an international, multidisciplinary workshop sponsored by the Pituitary Society offers evidence-based graded consensus recommendations and key summary points for clinical practice on the diagnosis and management of prolactinomas. Epidemiology and pathogenesis, clinical presentation of disordered pituitary hormone secretion, assessment of hyperprolactinaemia and biochemical evaluation, optimal use of imaging strategies and disease-related complications are addressed. In-depth discussions present the latest evidence on treatment of prolactinoma, including efficacy, adverse effects and options for withdrawal of dopamine agonist therapy, as well as indications for surgery, preoperative medical therapy and radiation therapy. Management of prolactinoma in special situations is discussed, including cystic lesions, mixed growth hormone-secreting and prolactin-secreting adenomas and giant and aggressive prolactinomas. Furthermore, considerations for pregnancy and fertility are outlined, as well as management of prolactinomas in children and adolescents, patients with an underlying psychiatric disorder, postmenopausal women, transgender individuals and patients with chronic kidney disease. The workshop concluded that, although treatment resistance is rare, there is a need for additional therapeutic options to address clinical challenges in treating these patients and a need to facilitate international registries to enable risk stratification and optimization of therapeutic strategies.

Pituitary adenoma or neuroendocrine tumour: the need for an integrated prognostic classification

In the 2022 fifth edition of the WHO Classification of Endocrine Tumours and of Central Nervous System Tumours, pituitary adenomas are reclassified as neuroendocrine tumours (NETs). This change confers an oncology label to neoplasms that are overwhelmingly benign. A comprehensive clinical classification schema is required to guide prognosis, therapy and outcomes for all patients with pituitary adenomas. Pituitary adenomas and NETs exhibit some morphological and ultrastructural similarities. However, unlike NETs, pituitary adenomas are highly prevalent, yet indolent and rarely become malignant. This Perspective presents the outcomes of an interdisciplinary international workshop that addressed the merit and clinical implications of the classification change of pituitary adenoma to NET. Many non-histological factors provide mechanistic insight and influence the prognosis and treatment of pituitary adenoma. We recommend the development of a comprehensive classification that integrates clinical, genetic, biochemical, radiological, pathological and molecular information for all anterior pituitary neoplasms.

Effects of Sleep Fragmentation and Estradiol Decline on Cortisol in a Human Experimental Model of Menopause

CONTEXT

Perturbations to the hypothalamic-pituitary-adrenal (HPA) axis have been hypothesized to increase postmenopausal cardiometabolic risk. Although sleep disturbance, a known risk factor for cardiometabolic disease, is prevalent during the menopause transition, it is unknown whether menopause-related sleep disturbance and estradiol decline disturb the HPA axis.

OBJECTIVE

We examined the effect of experimental fragmentation of sleep and suppression of estradiol as a model of menopause on cortisol levels in healthy young women.

METHODS

Twenty-two women completed a 5-night inpatient study during the mid-to-late follicular phase (estrogenized). A subset (n = 14) repeated the protocol after gonadotropin-releasing hormone agonist-induced estradiol suppression. Each inpatient study included 2 unfragmented sleep nights followed by 3 experimental sleep fragmentation nights. This study took place with premenopausal women at an academic medical center. Interventions included sleep fragmentation and pharmacological hypoestrogenism, and main outcome measures were serum bedtime cortisol levels and cortisol awakening response (CAR).

RESULTS

Bedtime cortisol increased 27% (P = .03) and CAR decreased 57% (P = .01) following sleep fragmentation compared to unfragmented sleep. Polysomnographic-derived wake after sleep-onset (WASO) was positively associated with bedtime cortisol levels (P = .047) and negatively associated with CAR (P < .01). Bedtime cortisol levels were 22% lower in the hypoestrogenized state compared to the estrogenized state (P = .02), while CAR was similar in both estradiol conditions (P = .38).

CONCLUSION

Estradiol suppression and modifiable menopause-related sleep fragmentation both independently perturb HPA axis activity. Sleep fragmentation, commonly seen in menopausal women, may disrupt the HPA axis, which in turn may lead to adverse health effects as women age.

Pilot study to define criteria for Pituitary Tumors Centers of Excellence (PTCOE): results of an audit of leading international centers

PURPOSE

The Pituitary Society established the concept and mostly qualitative parameters for defining uniform criteria for Pituitary Tumor Centers of Excellence (PTCOEs) based on expert consensus. Aim of the study was to validate those previously proposed criteria through collection and evaluation of self-reported activity of several internationally-recognized tertiary pituitary centers, thereby transforming the qualitative 2017 definition into a validated quantitative one, which could serve as the basis for future objective PTCOE accreditation.

METHODS

An ad hoc prepared database was distributed to nine Pituitary Centers chosen by the Project Scientific Committee and comprising Centers of worldwide repute, which agreed to provide activity information derived from registries related to the years 2018-2020 and completing the database within 60 days. The database, provided by each center and composed of Excel® spreadsheets with requested specific information on leading and supporting teams, was reviewed by two blinded referees and all 9 candidate centers satisfied the overall PTCOE definition, according to referees' evaluations. To obtain objective numerical criteria, median values for each activity/parameter were considered as the preferred PTCOE definition target, whereas the low limit of the range was selected as the acceptable target for each respective parameter.

RESULTS

Three dedicated pituitary neurosurgeons are preferred, whereas one dedicated surgeon is acceptable. Moreover, 100 surgical procedures per center per year are preferred, while the results indicated that 50 surgeries per year are acceptable. Acute post-surgery complications, including mortality and readmission rates, should preferably be negligible or nonexistent, but acceptable criterion is a rate lower than 10% of patients with complications requiring readmission within 30 days after surgery. Four endocrinologists devoted to pituitary diseases are requested in a PTCOE and the total population of patients followed in a PTCOE should not be less than 850. It appears acceptable that at least one dedicated/expert in pituitary diseases is present in neuroradiology, pathology, and ophthalmology groups, whereas at least two expert radiation oncologists are needed.

CONCLUSION

This is, to our knowledge, the first study to survey and evaluate the activity of a relevant number of high-volume centers in the pituitary field. This effort, internally validated by ad hoc reviewers, allowed for transformation of previously formulated theoretical criteria for the definition of a PTCOE to precise numerical definitions based on real-life evidence. The application of a derived synopsis of criteria could be used by independent bodies for accreditation of pituitary centers as PTCOEs.

Familial central precocious puberty due to DLK1 deficiency: novel genetic findings and relevance of serum DLK1 levels

BACKGROUND

Several rare loss-of-function mutations of delta-like noncanonical notch ligand 1 (DLK1) have been described in non-syndromic children with familial central precocious puberty (CPP).

OBJECTIVE

We investigated genetic abnormalities of DLK1 gene in a French cohort of children with idiopathic CPP. Additionally, we explored the pattern of DLK1 serum levels in patients with CPP and in healthy children at puberty, as well as in wild-type female mice.

PATIENTS AND METHODS

Genomic DNA was obtained from 121 French index cases with CPP. Automated sequencing of the coding region of the DLK1 gene was performed in all cases. Serum DLK1 levels were measured by enzyme linked immunosorbent assay (ELISA) in 209 individuals, including 191 with normal pubertal development and in female mice during postnatal pubertal maturation.

RESULTS

We identified 2 rare pathogenic DLK1 allelic variants: A stop gain variant (c.372C>A; p.Cys124X) and a start loss variant (c.2T>G; p.Met1?, or p.0) in 2 French girls with CPP. Mean serum DLK1 levels were similar between healthy children and idiopathic CPP children. In healthy individuals, DLK1 levels correlated with pubertal stage: In girls, DLK1 decreased between Tanner stages III and V, whereas in boys, DLK1 decreased between Tanner stages II and V (P = .008 and .016, respectively). Serum levels of Dlk1 also decreased in wild-type female mice.

CONCLUSIONS

Novel loss-of-function mutations in DLK1 gene were identified in 2 French girls with CPP. Additionally, we demonstrated a pattern of dynamic changes in circulating DLK1 serum levels in humans and mice during pubertal stages, reinforcing the role of this factor in pubertal timing.

A 72-Year-Old Woman with Fatigue and Shortness of Breath

A 72-Year-Old Woman with Fatigue and Shortness of BreathA 72-year-old woman presented for evaluation of fatigue, dyspnea on exertion, and weight loss. How do you approach the evaluation, and what is the most likely diagnosis?

Mouse Testicular Mkrn3 Expression Is Primarily Interstitial, Increases Peripubertally, and Is Responsive to LH/hCG

Studies in humans and mice support a role for Makorin RING finger protein 3 (MKRN3) as an inhibitor of gonadotropin-releasing hormone (GnRH) secretion prepubertally, and its loss of function is the most common genetic cause of central precocious puberty in humans. Studies have shown that the gonads can synthesize neuropeptides and express MKRN3/Mkrn3 mRNA. Therefore, we aimed to investigate the spatiotemporal expression pattern of Mkrn3 in gonads during sexual development, and its potential regulation in the functional testicular compartments by gonadotropins. Mkrn3 mRNA was detected in testes and ovaries of wild-type mice at all ages evaluated, with a sexually dimorphic expression pattern between male and female gonads. Mkrn3 expression was highest peripubertally in the testes, whereas it was lower peripubertally than prepubertally in the ovaries. Mkrn3 is expressed primarily in the interstitial compartment of the testes but was also detected at low levels in the seminiferous tubules. In vitro studies demonstrated that Mkrn3 mRNA levels increased in human chorionic gonadotropin (hCG)-treated Leydig cell primary cultures. Acute administration of a GnRH agonist in adult mice increased Mkrn3 expression in testes, whereas inhibition of the hypothalamic-pituitary-gonadal axis by chronic administration of GnRH agonist had the opposite effect. Finally, we found that hCG increased Mkrn3 mRNA levels in a dose-dependent manner. Taken together, our developmental expression analyses, in vitro and in vivo studies show that Mkrn3 is expressed in the testes, predominantly in the interstitial compartment, and that Mkrn3 expression increases after puberty and is responsive to luteinizing hormone/hCG stimulation.

Rare variants in the MECP2 gene in girls with central precocious puberty: a translational cohort study

BACKGROUND

Identification of genetic causes of central precocious puberty have revealed epigenetic mechanisms as regulators of human pubertal timing. MECP2, an X-linked gene, encodes a chromatin-associated protein with a role in gene transcription. MECP2 loss-of-function mutations usually cause Rett syndrome, a severe neurodevelopmental disorder. Early pubertal development has been shown in several patients with Rett syndrome. The aim of this study was to explore whether MECP2 variants are associated with an idiopathic central precocious puberty phenotype.

METHODS

In this translational cohort study, participants were recruited from seven tertiary centres from five countries (Brazil, Spain, France, the USA, and the UK). Patients with idiopathic central precocious puberty were investigated for rare potentially damaging variants in the MECP2 gene, to assess whether MECP2 might contribute to the cause of central precocious puberty. Inclusion criteria were the development of progressive pubertal signs (Tanner stage 2) before the age of 8 years in girls and 9 years in boys and basal or GnRH-stimulated LH pubertal concentrations. Exclusion criteria were the diagnosis of peripheral precocious puberty and the presence of any recognised cause of central precocious puberty (CNS lesions, known monogenic causes, genetic syndromes, or early exposure to sex steroids). All patients included were followed up at the outpatient clinics of participating academic centres. We used high-throughput sequencing in 133 patients and Sanger sequencing of MECP2 in an additional 271 patients. Hypothalamic expression of Mecp2 and colocalisation with GnRH neurons were determined in mice to show expression of Mecp2 in key nuclei related to pubertal timing regulation.

FINDINGS

Between Jun 15, 2020, and Jun 15, 2022, 404 patients with idiopathic central precocious puberty (383 [95%] girls and 21 [5%] boys; 261 [65%] sporadic cases and 143 [35%] familial cases from 134 unrelated families) were enrolled and assessed. We identified three rare heterozygous likely damaging coding variants in MECP2 in five girls: a de novo missense variant (Arg97Cys) in two monozygotic twin sisters with central precocious puberty and microcephaly; a de novo missense variant (Ser176Arg) in one girl with sporadic central precocious puberty, obesity, and autism; and an insertion (Ala6_Ala8dup) in two unrelated girls with sporadic central precocious puberty. Additionally, we identified one rare heterozygous 3'UTR MECP2 insertion (36_37insT) in two unrelated girls with sporadic central precocious puberty. None of them manifested Rett syndrome. Mecp2 protein colocalised with GnRH expression in hypothalamic nuclei responsible for GnRH regulation in mice.

INTERPRETATION

We identified rare MECP2 variants in girls with central precocious puberty, with or without mild neurodevelopmental abnormalities. MECP2 might have a role in the hypothalamic control of human pubertal timing, adding to the evidence of involvement of epigenetic and genetic mechanisms in this crucial biological process.

FUNDING

Fundação de Amparo à Pesquisa do Estado de São Paulo, Conselho Nacional de Desenvolvimento Científico e Tecnológico, and the Wellcome Trust.

Novel MKRN3 Missense Mutations Associated With Central Precocious Puberty Reveal Distinct Effects on Ubiquitination

CONTEXT

Loss-of-function mutations in the maternally imprinted genes, MKRN3 and DLK1, are associated with central precocious puberty (CPP). Mutations in MKRN3 are the most common known genetic etiology of CPP.

OBJECTIVE

This work aimed to screen patients with CPP for MKRN3 and DLK1 mutations and analyze the effects of identified mutations on protein function in vitro.

METHODS

Participants included 84 unrelated children with CPP (79 girls, 5 boys) and, when available, their first-degree relatives. Five academic medical institutions participated. Sanger sequencing of MKRN3 and DLK1 5' upstream flanking and coding regions was performed on DNA extracted from peripheral blood leukocytes. Western blot analysis was performed to assess protein ubiquitination profiles.

RESULTS

Eight heterozygous MKRN3 mutations were identified in 9 unrelated girls with CPP. Five are novel missense mutations, 2 were previously identified in patients with CPP, and 1 is a frameshift variant not previously associated with CPP. No pathogenic variants were identified in DLK1. Girls with MKRN3 mutations had an earlier age of initial pubertal signs and higher basal serum luteinizing hormone and follicle-stimulating hormone compared to girls with CPP without MRKN3 mutations. Western blot analysis revealed that compared to wild-type MKRN3, mutations within the RING finger domain reduced ubiquitination whereas the mutations outside this domain increased ubiquitination.

CONCLUSION

MKRN3 mutations were present in 10.7% of our CPP cohort, consistent with previous studies. The novel identified mutations in different domains of MKRN3 revealed different patterns of ubiquitination, suggesting distinct molecular mechanisms by which the loss of MRKN3 results in early pubertal onset.

Influence of gonadectomy on muscle health in micro- and partial-gravity environments in rats

Gonadal hormones, such as testosterone and estradiol, modulate muscle size and strength in males and females. However, the influence of sex hormones on muscle strength in micro- and partial-gravity environments (e.g., the Moon or Mars) is not fully understood. The purpose of this study was to determine the influence of gonadectomy (castration/ovariectomy) on progression of muscle atrophy in both micro- and partial-gravity environments in male and female rats. Male and female Fischer rats (n = 120) underwent castration/ovariectomy (CAST/OVX) or sham surgery (SHAM) at 11 wk of age. After 2 wk of recovery, rats were exposed to hindlimb unloading (0 g), partial weight bearing at 40% of normal loading (0.4 g, Martian gravity), or normal loading (1.0 g) for 28 days. In males, CAST did not exacerbate body weight loss or other metrics of musculoskeletal health. In females, OVX animals tended to have greater body weight loss and greater gastrocnemius loss. Within 7 days of exposure to either microgravity or partial gravity, females had detectable changes to estrous cycle, with greater time spent in low-estradiol phases diestrus and metestrus (∼47% in 1 g vs. 58% in 0 g and 72% in 0.4 g animals, P = 0.005). We conclude that in males testosterone deficiency at the initiation of unloading has little effect on the trajectory of muscle loss. In females, initial low estradiol status may result in greater musculoskeletal losses.NEW & NOTEWORTHY We find that removal of gonadal hormones does not exacerbate muscle loss in males or females during exposure to either simulated microgravity or partial-gravity environments. However, simulated micro- and partial gravity did affect females' estrous cycles, with more time spent in low-estrogen phases. Our findings provide important data on the influence of gonadal hormones on the trajectory of muscle loss during unloading and will help inform NASA for future crewed missions to space and other planets.

MKRN3 inhibits puberty onset via interaction with IGF2BP1 and regulation of hypothalamic plasticity

Makorin ring finger protein 3 (MKRN3) was identified as an inhibitor of puberty initiation with the report of loss-of-function mutations in association with central precocious puberty. Consistent with this inhibitory role, a prepubertal decrease in Mkrn3 expression was observed in the mouse hypothalamus. Here, we investigated the mechanisms of action of MKRN3 in the central regulation of puberty onset. We showed that MKRN3 deletion in hypothalamic neurons derived from human induced pluripotent stem cells was associated with significant changes in expression of genes controlling hypothalamic development and plasticity. Mkrn3 deletion in a mouse model led to early puberty onset in female mice. We found that Mkrn3 deletion increased the number of dendritic spines in the arcuate nucleus but did not alter the morphology of GnRH neurons during postnatal development. In addition, we identified neurokinin B (NKB) as an Mkrn3 target. Using proteomics, we identified insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) as another target of MKRN3. Interactome analysis revealed that IGF2BP1 interacted with MKRN3, along with several members of the polyadenylate-binding protein family. Our data show that one of the mechanisms by which MKRN3 inhibits pubertal initiation is through regulation of prepubertal hypothalamic development and plasticity, as well as through effects on NKB and IGF2BP1.

The Congenital and Acquired Mechanisms Implicated in the Etiology of Central Precocious Puberty

The etiology of central precocious puberty (CPP) is multiple and heterogeneous, including congenital and acquired causes that can be associated with structural or functional brain alterations. All causes of CPP culminate in the premature pulsatile secretion of hypothalamic GnRH and, consequently, in the premature reactivation of hypothalamic-pituitary-gonadal axis. The activation of excitatory factors or suppression of inhibitory factors during childhood represent the 2 major mechanisms of CPP, revealing a delicate balance of these opposing neuronal pathways. Hypothalamic hamartoma (HH) is the most well-known congenital cause of CPP with central nervous system abnormalities. Several mechanisms by which hamartoma causes CPP have been proposed, including an anatomical connection to the anterior hypothalamus, autonomous neuroendocrine activity in GnRH neurons, trophic factors secreted by HH, and mechanical pressure applied to the hypothalamus. The importance of genetic and/or epigenetic factors in the underlying mechanisms of CPP has grown significantly in the last decade, as demonstrated by the evidence of genetic abnormalities in hypothalamic structural lesions (eg, hamartomas, gliomas), syndromic disorders associated with CPP (Temple, Prader-Willi, Silver-Russell, and Rett syndromes), and isolated CPP from monogenic defects (MKRN3 and DLK1 loss-of-function mutations). Genetic and epigenetic discoveries involving the etiology of CPP have had influence on the diagnosis and familial counseling providing bases for potential prevention of premature sexual development and new treatment targets in the future. Global preventive actions inducing healthy lifestyle habits and less exposure to endocrine-disrupting chemicals during the lifespan are desirable because they are potentially associated with CPP.

Long-Term Changes in the Size of Pituitary Microadenomas

BACKGROUND

The estimated prevalence of pituitary lesions is 10% to 38.5% in radiologic studies. However, how frequently these incidental lesions should be monitored by serial pituitary magnetic resonance imaging (MRI) remains unclear.

OBJECTIVE

To evaluate changes in pituitary microadenomas over time.

DESIGN

Retrospective, longitudinal cohort study.

SETTING

Mass General Brigham, Boston, Massachusetts.

PATIENTS

Evidence of pituitary microadenoma from MRI.

MEASUREMENTS

Dimensions of pituitary microadenomas.

RESULTS

During the study period (from 2003 to 2021), 414 patients with pituitary microadenomas were identified. Of the 177 patients who had more than 1 MRI, 78 had no change in the size of the microadenoma over time, 49 had an increase in size, 34 had a decrease in size, and 16 had both an increase and decrease in size. By linear mixed model analysis, the estimated slope was 0.016 mm/y (95% CI, -0.037 to 0.069). In the subgroup analysis, pituitary adenomas with a baseline size of 4 mm or less tended to increase in size. The estimated slope was 0.09 mm/y (CI, 0.020 to 0.161). In contrast, in the subgroup with baseline tumor size greater than 4 mm, the size tended to decrease. The estimated slope was -0.063 mm/y (CI, -0.141 to 0.015).

LIMITATION

Retrospective cohort, some patients were lost to follow-up for unknown reasons, and data were limited to local large institutions.

CONCLUSION

During the study period, approximately two thirds of the microadenomas remained unchanged or decreased in size. The growth, if any, was slow. These findings suggest that less frequent pituitary MRI surveillance for patients with incidental pituitary microadenomas may be safe.

PRIMARY FUNDING SOURCE

None.

Early Onset GH Excess: Somatotroph Adenoma in a Young Adult

GH-secreting pituitary adenomas can cause gigantism or acromegaly, determined by onset before or after epiphyseal fusion of the distal ends of the radius and ulna. Overlapping phenotypes can occur when the condition presents peripubertally. Gigantism is associated with identifiable hereditary causes and genetic mutations in almost 50% of cases; genetic testing should be considered in patients with gigantism and early-onset acromegaly, especially (but not only) when pituitary tumors have aggressive features and/or are refractory to standard treatments. Here, we present a case of a young adult with a giant somatotroph adenoma resistant to multiple treatment modalities and negative for mutations in AIP, which encodes aryl hydrocarbon receptor-interacting protein.

Molecular basis of normal and pathological puberty: from basic mechanisms to clinical implications

Puberty is a major maturational event; its mechanisms and timing are driven by genetic determinants, but also controlled by endogenous and environmental cues. Substantial progress towards elucidation of the neuroendocrine networks governing puberty has taken place. However, key aspects of the mechanisms responsible for the precise timing of puberty and its alterations have only recently begun to be deciphered, propelled by epidemiological data suggesting that pubertal timing is changing in humans, via mechanisms that are not yet understood. By integrating basic and clinical data, we provide a comprehensive overview of current advances on the physiological basis of puberty, with a particular focus on the roles of kisspeptins and other central transmitters, the underlying molecular and endocrine mechanisms, and the pathways involved in pubertal modulation by nutritional and metabolic cues. Additionally, we have summarised molecular features of precocious and delayed puberty in both sexes, as revealed by clinical and genetic studies. This Review is a synoptic up-to-date view of how puberty is controlled and of the pathogenesis of major pubertal alterations, from both a clinical and translational perspective. We also highlight unsolved challenges that will seemingly concentrate future research efforts in this active domain of endocrinology.

Clinical Biology of the Pituitary Adenoma

All endocrine glands are susceptible to neoplastic growth, yet the health consequences of these neoplasms differ between endocrine tissues. Pituitary neoplasms are highly prevalent and overwhelmingly benign, exhibiting a spectrum of diverse behaviors and impact on health. To understand the clinical biology of these common yet often innocuous neoplasms, we review pituitary physiology and adenoma epidemiology, pathophysiology, behavior, and clinical consequences. The anterior pituitary develops in response to a range of complex brain signals integrating with intrinsic ectodermal cell transcriptional events that together determine gland growth, cell type differentiation, and hormonal production, in turn maintaining optimal endocrine health. Pituitary adenomas occur in 10% of the population; however, the overwhelming majority remain harmless during life. Triggered by somatic or germline mutations, disease-causing adenomas manifest pathogenic mechanisms that disrupt intrapituitary signaling to promote benign cell proliferation associated with chromosomal instability. Cellular senescence acts as a mechanistic buffer protecting against malignant transformation, an extremely rare event. It is estimated that fewer than one-thousandth of all pituitary adenomas cause clinically significant disease. Adenomas variably and adversely affect morbidity and mortality depending on cell type, hormone secretory activity, and growth behavior. For most clinically apparent adenomas, multimodal therapy controlling hormone secretion and adenoma growth lead to improved quality of life and normalized mortality. The clinical biology of pituitary adenomas, and particularly their benign nature, stands in marked contrast to other tumors of the endocrine system, such as thyroid and neuroendocrine tumors.

OR17-1 MKRN3 Inhibits the Reproductive Axis by Interacting With Key Hypothalamic Substrates and Targeting Neurokinin B to Degradation Pathways

Background and Objectives

Human fertility is attained following puberty due to finely orchestrated events driven by hypothalamic release of the excitatory neuropeptide neurokinin B (NKB), which in turn stimulates the release of kisspeptin and then GnRH to activate the downstream pituitary-gonadal axis. Our group has identified that loss-of-function mutations in Makorin Ring Finger Protein 3 (MKRN3) cause central precocious puberty (CPP). Mkrn3 is highly expressed in the hypothalamus of both male and female mice in early postnatal life, then declines prior to the onset of puberty. Mutations in MKRN3 E3 ubiquitin ligase domain, identified in patients with CPP, result in reduced auto-ubiquitination. However, the mechanisms of action of MKRN3 and its targets remain largely unknown. We hypothesized that MKRN3 inhibits the reproductive axis through interactions with hypothalamic substrates, targeting them to degradation pathways.

Methods and Results

Using interactome analysis and candidate approaches in vitro, we identified poly(A) binding protein cytoplasmic 1 and 4 (PABPC1 and 4) and insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) as MKRN3 interactors, consistent with reports from other research groups. Additionally, our proteomic analysis revealed that Igf2bp1 levels are increased in the hypothalamus of Mkrn3 knockout (KO) mice versus wild type animals. Remarkably, we found that MKRN3-IGF2BP1 interaction is mediated by RNA, as their interaction was abrogated by RNase treatment. However, an MKRN3 missense mutation associated with CPP, p.C364F, within the E3 ubiquitin ligase domain, did not affect the RNA mediated interaction. Preliminary data from RNA co-IP, aiming to identify putative RNA targets, suggested that MKRN3 and IGF2BP1 bind to TAC3 mRNA. We further identified an increase in Nkb protein levels in the hypothalamus of Mkrn3 KO mice. We also showed that NKB is a substrate of MKRN3 E3 ubiquitin ligase activity in vitro by demonstrating increased ubiquitination of NKB in cells co-transfected with expression vectors encoding MKRN3 and NKB and treated with proteasome inhibitor. Additionally, MKRN3 overexpression resulted in degradation of NKB protein by western blot analysis, and alteration of NKB intracellular localization by immunofluorescence. These effects were impaired by MKRN3 missense mutations (p.C340G and p.C364F) in the E3 ubiquitin ligase motif, suggesting a pathophysiological mechanism of MKRN3 mutations in CPP.

Conclusions

We identified that MKRN3 interacts with PABPC1, PABPC4 and IGF2BP1 and targets NKB to degradation. We showed that NKB degradation was mediated by the MKRN3 E3 ubiquitin ligase domain, as mutations within this motif abrogated NKB degradation. However, this mutation did not affect MKRN3 RNA-mediated binding to IGF2BP1, highlighting that multiple domains of MKRN3 may contribute to its actions. Here, we propose a mechanism by which MKRN3, interacting with PABPCs and IGF2BP1 and targeting NKB for degradation, may act to inhibit the reproductive axis.

Presentation: Sunday, June 12, 2022 11:00 a.m. - 11:15 a.m.

Hypothalamic Overexpression of Makorin Ring Finger Protein 3 Results in Delayed Puberty in Female Mice

Makorin ring finger protein 3 (MKRN3) is an important neuroendocrine player in the control of pubertal timing and upstream inhibitor of gonadotropin-releasing hormone secretion. In mice, expression of Mkrn3 in the hypothalamic arcuate and anteroventral periventricular nucleus is high early in life and declines before the onset of puberty. Therefore, we aimed to explore if the persistence of hypothalamic Mkrn3 expression peripubertally would result in delayed puberty. Female mice that received neonatal bilateral intracerebroventricular injections of a recombinant adeno-associated virus expressing Mkrn3 had delayed vaginal opening and first estrus compared with animals injected with control virus. Subsequent estrous cycles and fertility were normal. Interestingly, male mice treated similarly did not exhibit delayed puberty onset. Kiss1, Tac2, and Pdyn mRNA levels were increased in the mediobasal hypothalamus in females at postnatal day 28, whereas kisspeptin and neurokinin B protein levels in the arcuate nucleus were decreased, following Mkrn3 overexpression, compared to controls. Cumulatively, these data suggest that Mkrn3 may directly or indirectly target neuropeptides of Kiss1 neurons to degradation pathways. This mouse model suggests that MKRN3 may be a potential contributor to delayed onset of puberty, in addition to its well-established roles in central precocious puberty and the timing of menarche.

Sleep Fragmentation and Estradiol Suppression Decrease Fat Oxidation in Premenopausal Women

CONTEXT

Body fat gain associated with menopause has been attributed to estradiol (E2) withdrawal. Hypoestrogenism is unlikely to be the only contributing factor, however.

OBJECTIVE

Given the links between sleep and metabolic health, we examined the effects of an experimental menopausal model of sleep fragmentation on energy metabolism.

METHODS

Twenty premenopausal women (age 21-45 years) underwent a 5-night inpatient study during the mid-to-late follicular phase (estrogenized; n = 20) and the same protocol was repeated in a subset of the participants (n = 9) following leuprolide-induced E2 suppression (hypo-estrogenized). During each 5-night study, there were 2 nights of unfragmented sleep followed by 3 nights of fragmented sleep. Indirect calorimetry was used to assess fasted resting energy expenditure (REE) and substrate oxidation.

RESULTS

Sleep fragmentation in the estrogenized state increased the respiratory exchange ratio (RER) and carbohydrate oxidation while decreasing fat oxidation (all P < 0.01). Similarly, in the hypo-estrogenized state without sleep fragmentation, RER and carbohydrate oxidation increased and fat oxidation decreased (all P < 0.01); addition of sleep fragmentation to the hypo-estrogenized state did not produce further effects beyond that observed for either intervention alone (P < 0.05). There were no effects of either sleep fragmentation or E2 state on REE.

CONCLUSION

Sleep fragmentation and hypoestrogenism each independently alter fasting substrate oxidation in a manner that may contribute to body fat gain. These findings are important for understanding mechanisms underlying propensity to body fat gain in women across the menopause transition.

Reproductive Phenotypes in Men With Acquired or Congenital Hypogonadotropic Hypogonadism: A Comparative Study

CONTEXT

In men with congenital hypogonadotropic hypogonadism (CHH), gonadotropin deficiency and testicular impairment exist since fetal development and persist throughout life. In a few reported cases of acquired HH (AHH), HH onset occurs mainly post pubertally.

OBJECTIVE

This work aimed to compare the natural history and reproductive status in large series of CHH and lesional AHH evaluated in a single expert academic center.

METHODS

We included 172 controls, 668 male HH patients (CHH: n = 201 [age 16.9 ± 9.0 years], lesional AHH: n = 467 [age 45.6 ± 18.4 years]) caused by hypothalamic and/or pituitary tumors (mainly adenomas and craniopharyngiomas) or infiltrative/traumatic diseases.

RESULTS

At diagnosis, CHH were significantly younger, with 52.9% diagnosed before age 18 years, compared to only 9.6% of AHH patients. Cryptorchidism (21.9% vs 0.3%) and micropenis were more prevalent in CHH than AHH patients. Low testicular volume (TV) was present in 97% of patients with CHH (mean TV: 3.4 ± 2.7 mL) but in only 30% of those with AHH (mean TV: 20.8 ± 5.0 mL). Whereas no men with persistent CHH had spontaneous fertility, 70.4% of AHH men fathered at least one child without medical therapy. Total testosterone was lower both in CHH and AHH patients than in controls. Compared to controls, circulating gonadotropins and testicular peptides (insulin-like factor-3 and inhibin B) were decreased both in CHH and AHH, but were significantly higher in patients with AHH.

CONCLUSION

In AHH patients, the HH has later onset and is less severe than in CHH and the phenotype can overlap with that of individuals with normal laboratory values. Our data suggest that age at diagnosis is a predictor of the reproductive phenotype in AHH.

Quality of life after long-term biochemical control of acromegaly

PURPOSE

To assess long-term quality of life (QoL) in patients with sustained biochemical control of acromegaly, comparing those receiving vs not receiving pharmacotherapy (primary analysis); to assess change in QoL over time (secondary analysis).

METHODS

Cross-sectional study, with a secondary longitudinal component, of 58 patients with biochemically controlled acromegaly. All had participated in studies assessing QoL years previously, after having undergone surgery ± radiotherapy. One cohort received medical therapy [MED (n = 33)]; the other did not [NO-MED (n = 25)]. QoL was assessed by the 36-Item-Short-Form Health Survey (SF-36), Acromegaly Quality of Life Questionnaire (AcroQoL), Gastrointestinal Quality of Life Index (GIQLI), Symptom Questionnaire, and QoL-Assessment of Growth Hormone Deficiency in Adults (QoL-AGHDA).

RESULTS

Mean (± SD) duration of biochemical control was 15.0 ± 6.4 years for MED and 20.4 ± 8.2 years for NO-MED (p = 0.007). 58% of subjects scored < 25% of normal on ≥ 1 SF-36 domain and 32% scored < 25% of normal on ≥ 4 of 8 domains. Comparing MED vs NO-MED and controlling for duration of biochemical control, there were no significant differences in QoL by SF-36, AcroQOL, GIQLI, Symptom Questionnaire, or QoL-AGHDA. Growth hormone deficiency (GHD) but not radiotherapy predicted poorer QoL. In MED, QoL improved over time in three AcroQoL domains and two GIQLI domains. In NO-MED, QoL worsened in two SF-36 domains and two Symptom Questionnaire domains; QoL-AGHDA scores also worsened in subjects with GHD.

CONCLUSION

A history of acromegaly and development of GHD, but not pharmacologic or radiotherapy, are detrimental to QoL, which remains poor over the long-term despite biochemical control.

Functional Rescue of Inactivating Mutations of the Human Neurokinin 3 Receptor Using Pharmacological Chaperones

G protein-coupled receptors (GPCRs) facilitate the majority of signal transductions across cell membranes in humans, with numerous diseases attributed to inactivating GPCR mutations. Many of these mutations result in misfolding during nascent receptor synthesis in the endoplasmic reticulum (ER), resulting in intracellular retention and degradation. Pharmacological chaperones (PCs) are cell-permeant small molecules that can interact with misfolded receptors in the ER and stabilise/rescue their folding to promote ER exit and trafficking to the cell membrane. The neurokinin 3 receptor (NK3R) plays a pivotal role in the hypothalamic–pituitary–gonadal reproductive axis. We sought to determine whether NK3R missense mutations result in a loss of cell surface receptor expression and, if so, whether a cell-permeant small molecule NK3R antagonist could be repurposed as a PC to restore function to these mutants. Quantitation of cell surface expression levels of seven mutant NK3Rs identified in hypogonadal patients indicated that five had severely impaired cell surface expression. A small molecule NK3R antagonist, M8, increased cell surface expression in four of these five and resulted in post-translational receptor processing in a manner analogous to the wild type. Importantly, there was a significant improvement in receptor activation in response to neurokinin B (NKB) for all four receptors following their rescue with M8. This demonstrates that M8 may have potential for therapeutic development in the treatment of hypogonadal patients harbouring NK3R mutations. The repurposing of existing small molecule GPCR modulators as PCs represents a novel and therapeutically viable option for the treatment of disorders attributed to mutations in GPCRs that cause intracellular retention.

Connecting nutritional deprivation and pubertal inhibition via GRK2-mediated repression of kisspeptin actions in GnRH neurons

BACKGROUND

Perturbations in the timing of puberty, with potential adverse consequences in later health, are increasingly common. The underlying neurohormonal mechanisms are unfolded, but nutritional alterations are key contributors. Efforts to unveil the basis of normal puberty and its metabolic control have focused on mechanisms controlling expression of Kiss1, the gene encoding the puberty-activating neuropeptide, kisspeptin. However, other regulatory phenomena remain ill-defined. Here, we address the putative role of the G protein-coupled-receptor kinase-2, GRK2, in GnRH neurons, as modulator of pubertal timing via repression of the actions of kisspeptin, in normal maturation and conditions of nutritional deficiency.

METHODS

Hypothalamic RNA and protein expression analyses were conducted in maturing female rats. Pharmacological studies involved central administration of GRK2 inhibitor, βARK1-I, and assessment of gonadotropin responses to kisspeptin or phenotypic and hormonal markers of puberty, under normal nutrition or early subnutrition in female rats. In addition, a mouse line with selective ablation of GRK2 in GnRH neurons, aka G-GRKO, was generated, in which hormonal responses to kisspeptin and puberty onset were monitored, in normal conditions and after nutritional deprivation.

RESULTS

Hypothalamic GRK2 expression increased along postnatal maturation in female rats, especially in the preoptic area, where most GnRH neurons reside, but decreased during the juvenile-to-pubertal transition. Blockade of GRK2 activity enhanced Ca+2 responses to kisspeptin in vitro, while central inhibition of GRK2 in vivo augmented gonadotropin responses to kisspeptin and advanced puberty onset. Postnatal undernutrition increased hypothalamic GRK2 expression and delayed puberty onset, the latter being partially reversed by central GRK2 inhibition. Conditional ablation of GRK2 in GnRH neurons enhanced gonadotropin responses to kisspeptin, accelerated puberty onset, and increased LH pulse frequency, while partially prevented the negative impact of subnutrition on pubertal timing and LH pulsatility in mice.

CONCLUSIONS

Our data disclose a novel pathway whereby GRK2 negatively regulates kisspeptin actions in GnRH neurons, as major regulatory mechanism for tuning pubertal timing in nutritionally-compromised conditions.

Oral Contraceptive and Menopausal Hormone Therapy Use and Risk of Pituitary Adenoma: Cohort and Case-Control Analyses

CONTEXT

No prospective epidemiologic studies have examined associations between use of oral contraceptives (OCs) or menopausal hormone therapy (MHT) and risk of pituitary adenoma in women.

OBJECTIVE

Our aim was to determine the association between use of OC and MHT and risk of pituitary adenoma in two separate datasets.

METHODS

We evaluated the association of OC/MHT with risk of pituitary adenoma in the Nurses' Health Study and Nurses' Health Study II by computing multivariable-adjusted hazard ratios (MVHR) of pituitary adenoma by OC/MHT use using Cox proportional hazards models. Simultaneously, we carried out a matched case-control study using an institutional data repository to compute multivariable-adjusted odds ratios (MVOR) of pituitary adenoma by OC/MHT use.

RESULTS

In the cohort analysis, during 6 668 019 person-years, 331 participants reported a diagnosis of pituitary adenoma. Compared to never-users, neither past (MVHR = 1.05; 95% CI, 0.80-1.36) nor current OC use (MVHR = 0.72; 95% CI, 0.40-1.32) was associated with risk. For MHT, compared to never-users, both past (MVHR = 2.00; 95% CI, 1.50-2.68) and current use (MVHR = 1.80; 95% CI, 1.27-2.55) were associated with pituitary adenoma risk, as was longer duration (MVHR = 2.06; 95% CI, 1.42-2.99 comparing more than 5 years of use to never, P trend = .002). Results were similar in lagged analyses, when stratified by body mass index, and among those with recent health care use. In the case-control analysis, we included 5469 cases. Risk of pituitary adenoma was increased with ever use of MHT (MVOR = 1.57; 95% CI, 1.35-1.83) and OC (MVOR = 1.27; 95% CI, 1.14-1.42) compared to never.

CONCLUSION

Compared to never use, current and past MHT use and longer duration of MHT use were positively associated with higher risk of pituitary adenoma in 2 independent data sets. OC use was not associated with risk in the prospective cohort analysis and was associated with only mildly increased risk in the case-control analysis.

Deletion of Gαq/11 or Gαs Proteins in Gonadotropes Differentially Affects Gonadotropin Production and Secretion in Mice

Gonadotropin-releasing hormone (GnRH) regulates gonadal function via its stimulatory effects on gonadotropin production by pituitary gonadotrope cells. GnRH is released from the hypothalamus in pulses and GnRH pulse frequency differentially regulates follicle-stimulating hormone (FSH) and luteinizing hormone (LH) synthesis and secretion. The GnRH receptor (GnRHR) is a G protein-coupled receptor that canonically activates Gα q/11-dependent signaling on ligand binding. However, the receptor can also couple to Gα s and in vitro data suggest that toggling between different G proteins may contribute to GnRH pulse frequency decoding. For example, as we show here, knockdown of Gα s impairs GnRH-stimulated FSH synthesis at low- but not high-pulse frequency in a model gonadotrope-derived cell line. We next used a Cre-lox conditional knockout approach to interrogate the relative roles of Gα q/11 and Gα s proteins in gonadotrope function in mice. Gonadotrope-specific Gα q/11 knockouts exhibit hypogonadotropic hypogonadism and infertility, akin to the phenotypes seen in GnRH- or GnRHR-deficient mice. In contrast, under standard conditions, gonadotrope-specific Gα s knockouts produce gonadotropins at normal levels and are fertile. However, the LH surge amplitude is blunted in Gα s knockout females and postgonadectomy increases in FSH and LH are reduced both in males and females. These data suggest that GnRH may signal principally via Gα q/11 to stimulate gonadotropin production, but that Gα s plays important roles in gonadotrope function in vivo when GnRH secretion is enhanced.

Consensus on diagnosis and management of Cushing's disease: a guideline update

Cushing's disease requires accurate diagnosis, careful treatment selection, and long-term management to optimise patient outcomes. The Pituitary Society convened a consensus workshop comprising more than 50 academic researchers and clinical experts to discuss the application of recent evidence to clinical practice. In advance of the virtual meeting, data from 2015 to present about screening and diagnosis; surgery, medical, and radiation therapy; and disease-related and treatment-related complications of Cushing's disease summarised in recorded lectures were reviewed by all participants. During the meeting, concise summaries of the recorded lectures were presented, followed by small group breakout discussions. Consensus opinions from each group were collated into a draft document, which was reviewed and approved by all participants. Recommendations regarding use of laboratory tests, imaging, and treatment options are presented, along with algorithms for diagnosis of Cushing's syndrome and management of Cushing's disease. Topics considered most important to address in future research are also identified.

Central precocious puberty: Recent advances in understanding the aetiology and in the clinical approach

Central precocious puberty (CPP) results from early activation of the hypothalamic-pituitary-gonadal (HPG) axis. The current state of knowledge of the complex neural network acting at the level of the hypothalamus and the GnRH neuron to control puberty onset has expanded, particularly in the context of molecular interactions. Along with these advances, the knowledge of pubertal physiology and pathophysiology has also increased. This review focuses on regulatory abnormalities occurring at the hypothalamic level of the HPG axis to cause CPP. The clinical approach to diagnosis of puberty and pubertal disorders is also reviewed, with a particular focus on aetiologies of CPP. The recent identification of mutations in MKRN3 and DLK1 in familial as well sporadic forms of CPP has changed the state of the art of the approach to patients with CPP. Genetic advances have also had important repercussions beyond consideration of puberty alone. Syndromic disorders and central nervous system lesions associated with CPP are also discussed. If untreated, these conditions may lead to adverse physical, psychosocial and medical outcomes.

The oestrous cycle and skeletal muscle atrophy: Investigations in rodent models of muscle loss

NEW FINDINGS

What is the central question of this study? Is the oestrous cycle affected during disuse atrophies and, if so, how are oestrous cycle changes related to musculoskeletal outcomes? What is the main finding and its importance? Rodent oestrous cycles were altered during disuse atrophy, which was correlated with musculoskeletal outcomes. However, the oestrous cycle did not appear to be changed by Lewis lung carcinoma, which resulted in no differences in muscle size in comparison to healthy control animals. These findings suggest a relationship between the oestrous cycle and muscle size during atrophic pathologies.

ABSTRACT

Recent efforts have focused on improving our understanding of female muscle physiology during exposure to muscle atrophic stimuli. A key feature of female rodent physiology is the oestrous cycle. However, it is not known how such stimuli interact with the oestrous cycle to influence muscle health. In this study, we investigated the impact of muscle atrophic stimuli on the oestrous cycle and how these alterations are correlated with musculoskeletal outcomes. A series of experiments were performed in female rodents, including hindlimb unloading (HU), HU followed by 24 h of reloading, HU combined with dexamethasone treatment, and Lewis lung carcinoma. The oestrous cycle phase was assessed throughout each intervention and correlated with musculoskeletal outcomes. Seven or 14 days of HU increased the duration in dioestrus or metoestrus (D/M; low hormones) and was negatively correlated with gastrocnemius mass. Time spent in D/M was also negatively correlated with changes in grip strength and bone density after HU, and with muscle recovery 24 h after the cessation of HU. The addition of dexamethasone strengthened these relationships between time in D/M and reduced musculoskeletal outcomes. However, in animals with Lewis lung carcinoma, oestrous cyclicity did not differ from that of control animals, and time spent in D/M was not correlated with either gastrocnemius mass or tumour burden. In vitro experiments suggested that enhanced protein synthesis induced by estrogen might protect against muscle atrophy. In conclusion, muscle atrophic insults are correlated with changes in the oestrous cycle, which are associated with deterioration in musculoskeletal outcomes. The magnitude of oestrous cycle alterations depends on the atrophic stimuli.

Sex-specific pubertal and metabolic regulation of Kiss1 neurons via Nhlh2

Hypothalamic Kiss1 neurons control gonadotropin-releasing hormone release through the secretion of kisspeptin. Kiss1 neurons serve as a nodal center that conveys essential regulatory cues for the attainment and maintenance of reproductive function. Despite this critical role, the mechanisms that control kisspeptin synthesis and release remain largely unknown. Using Drop-Seq data from the arcuate nucleus of adult mice and in situ hybridization, we identified Nescient Helix-Loop-Helix 2 (Nhlh2), a transcription factor of the basic helix-loop-helix family, to be enriched in Kiss1 neurons. JASPAR analysis revealed several binding sites for NHLH2 in the Kiss1 and Tac2 (neurokinin B) 5' regulatory regions. In vitro luciferase assays evidenced a robust stimulatory action of NHLH2 on human KISS1 and TAC3 promoters. The recruitment of NHLH2 to the KISS1 and TAC3 promoters was further confirmed through chromatin immunoprecipitation. In vivo conditional ablation of Nhlh2 from Kiss1 neurons using Kiss1Cre:Nhlh2fl/fl mice induced a male-specific delay in puberty onset, in line with a decrease in arcuate Kiss1 expression. Females retained normal reproductive function albeit with irregular estrous cycles. Further analysis of male Kiss1Cre:Nhlh2fl/fl mice revealed higher susceptibility to metabolic challenges in the release of luteinizing hormone and impaired response to leptin. Overall, in Kiss1 neurons, Nhlh2 contributes to the metabolic regulation of kisspeptin and NKB synthesis and release, with implications for the timing of puberty onset and regulation of fertility in male mice.

Characterization of Gonadotroph Pituitary Adenomas Based on the Recent 2017 WHO Pituitary Tumor Classification

Introduction: More than 20% of pituitary adenomas are nonfunctional, the majority of which are of gonadotroph origin. Whereas previously, immunohistochemistry of pituitary hormones was used to classify adenoma subtypes, in 2017 the World Health Organization (WHO) reclassified pituitary adenomas using transcription factor expression in addition to immunohistochemistry. With this change, clinically nonfunctional gonadotroph adenomas can be distinguished among: (1) those staining for the transcription factor SF-1 and gonadotropins FSH and/or LH (FSH/LH+), (2) those that stain for SF-1 but not for FSH or LH (FSH/LH- SF1+), and (3) true null cell adenomas. It is unclear whether these three subgroups behave similarly clinically, or if they have distinct manifestations or outcomes. Our aim was to characterize these subgroups in regard to tumor size, recurrence and pituitary insufficiency.

Methods: In a retrospective chart review, 71 patients from 2017-2020 who presented to the hospital for transsphenoidal resection of clinically nonfunctioning pituitary adenomas were reviewed. All patients with pituitary adenomas that stained positive for SF-1 and negative for T-PIT and PIT-1, and tumors that were negative for all three transcription factors were evaluated. Those lacking clinical data were excluded. Clinical characteristics examined include: demographics, tumor size, invasion of cavernous sinus, and hormone deficiencies.

Results: Of the 71 pituitary tumors, 45% (n=32) stained positive for the beta subunit FSH and/or LH (FSH/LH+) and SF-1, 44% (n=31) stained for SF-1 with negative pituitary hormone stains (FSH/LH- SF1+), and 11% (n=8) were negative for all transcription factors and hormones (true null). All tumors were macroadenomas (&gt;1 cm). While there were &gt;50% males in the FSH/LH+ and FSH/LH- SF1+ groups, in the true null group only 25% of patients were male. Most patients were &gt;50 years old in all 3 groups (81% FSH/LH+, 75% FSH/LH- SF1+, 88% true null). The prevalence of cavernous sinus involvement was 36% in both groups that stained for SF-1, but was 62% in the true null group. Both SF-1+ groups had similar tumor sizes and prevalence of panhypopituitarism (15-21%), but there were more episodes of recurrence since last known follow up in the FSH/LH- SF1+ group (20%), compared to FSH/LH+ tumors (7%). The true null group had ≥50% rates for both panhypopituitarism and recurrence.

Conclusions: In this study, we highlighted the category of FSH/LH- SF1+ gonadotroph adenomas and compared these to FSH/LH+ and true null cell tumors. Based on clinical features, FSH/LH- SF1+ gonadotroph adenomas are similar to FSH/LH+ staining pituitary adenomas in regard to age, sex, size, and degree of cavernous sinus invasion, although there were more recurrences in the FSH/LH- SF1+ group. Though less common, our cohort suggests more aggressive tendencies in the true null group compared to SF-1 staining tumors.

Pubertal Onset Occurs in Female Mice Lacking Paternally Expressed Dlk1 Despite Lower Leptin and Kisspeptin Levels

The timing of puberty in females is highly sensitive to metabolic cues and energy reserves. Epidemiologic studies indicate a relationship between increased body mass index and earlier puberty in girls. In contrast, a significant delay in puberty and menarche is seen in girls who have diminished body fat. Multiple peripheral hormones are responsible for transmitting metabolic information to hypothalamic kisspeptin and GnRH neurons. Sufficient levels of leptin, an adipose tissue hormone with a permissive/stimulatory effect on the metabolic control of reproduction, are required for puberty onset, reproductive function and fertility. Loss-of-function mutations in the Delta-like homolog 1 (DLK1) gene have been described in girls with central precocious puberty (CPP) and increased body fat, suggesting a link between metabolism and reproduction. DLK1 is a paternally expressed gene located on human chromosome 14q32.2 in a locus associated with Temple syndrome (TS). Dlk1 knockout mice display pre- and postnatal growth retardation, a phenotype that overlaps with TS. We have shown that Dlk1 deficient female mice achieved puberty at the same age as wild type mice, despite a considerably lower body weight (BW) (“relative precocious puberty”). To date, the mechanisms of action of Dlk1 in determining pubertal onset remain unknown. In this study, we used a Dlk1 deficient mouse model to explore the influence of Dlk1 in the regulation of reproductive axis, particularly its effects on leptin and/or kisspeptin, a major excitatory factor of the reproductive axis. By RT-qPCR and Western blot, we confirmed that both Dlk1 mRNA and protein were undetectable in the mediobasal hypothalamus (MBH) of Dlk+/p- (which inherited the mutant allele from their father), but it was present in Dlk+/+ mice. White adipose tissue (WAT) and blood were collected from Dlk+/p- and Dlk+/+ female mice at postnatal day (PND) 26, and MBH tissue was obtained from both groups at PND 15, 26 and 60. Quantification of total WAT showed no significant difference between Dlk1+/p-and Dlk1+/+ mice (p=0.8) at PND26, even after correction for total BW (p=0.29). Hypothalamic mRNA levels of Kiss1 and Socs3, a downstream mediator of leptin signaling, were measured by RT-qPCR. Kiss1 mRNA levels were significantly reduced in the MBH of Dlk1+/p- mice at PND15 and PND60, but no significant difference was found at PND 26. Socs3 expression was significantly lower in Dlk1+/p- mice (p=0.04) as a result of the reduced circulating levels of leptin (ELISA) observed in these mice at PDN26 (p=0.01). Our findings suggest that the absence of Dlk1 may attenuate the metabolic effects of low body weight and low leptin levels on puberty onset and that, as seen in humans, DLK1 is an important link between body weight and pubertal development. Finally, Dlk1 deficiency leads to activation of the reproductive axis despite lower levels of kisspeptin.

Pegvisomant as Monotherapy or Combination Therapy in Somatostatin Refractory Acromegaly

Background: Pegvisomant, a growth hormone antagonist, has been widely used as monotherapy or combination therapy with somatostatin (SST) analogs and/or dopamine agonists in acromegaly poorly controlled by SST analogs. Limited information is available to compare pegvisomant monotherapy, combination with SST analogs or dopamine agonists, and combination of all three agents.

Method: In this retrospective cohort study, we identified 23 patients with SST analog refractory acromegaly who received pegvisomant as monotherapy or in combination with SST analogs and/or dopamine agonists through the Research Patient Data Registry. We divided the patients into four groups: Group 1. pegvisomant alone (n=8); Group 2. pegvisomant plus a SST analog (pasireotide, octreotide or lanreotide) (n=8); Group 3. pegvisomant plus cabergoline (n=5) Group 4. Pegvisomant plus SST analog and dopamine agonist (n=2). We analyzed the changes in IGF-1, HbA1C, ALT and AST, blood pressure, and radiographic tumor size before and 6 months after treatment.

Results: In 6 months, the mean IGF-1 level (ng/ml) changed from baseline 482 to 290 and decreased by 40% (P = 0.050) in group 1, changed from baseline 623 to 291 and decreased by 53% (P= 0.003) in group 2, changed from baseline 579 to 367 and decreased by 36% (p = 0.100) in group 3, and decreased 47% from 609 to 326 (P= 0.100) in group 4.

The mean systolic blood pressure (mmHg) before and 6 months after treatment changed from 139 to 128 (p = 0.001) in group 1, changed from 130 to 126 (p = 0.553) in group 2, changed from 134 to 126 (p = 0.373) in group 3, and changed from 125 to 127 (p= 0.700) in group 4. Diastolic blood pressure (mmHg) changed from 82 to 76 (P = 0.110) in group 1, changed from 79 to 76 (p = 0.325) in group 2, changed from 80 to 74 (p=0.002) in group 3, and changed from 80 to 75 (p=0.126) in group 4.

There were no significant changes in ALT and AST and A1C before and 6 months after treatment in all groups. In terms of radiographic tumor size change before and 6 months after the treatment, there was no change in tumor size in 5 of 5 patients in group 1. In group 2, the tumor size in 4 of 7 remained unchanged but 3 of 7 patients had increased tumor sizes. In group 3, there was no change in tumor size in 3 of 3 patients. In group 4, there was no change in tumor size in 2 of 2 patients.

Conclusion: Our results suggest that in somatostain analog refractory acromegaly, combination pegvisomant and a SST analog significantly decreased IGF-1 level although decrease in IGF-1 in pegvisomant monotherapy almost reach statistical significance (P = 0.050). Although there was a trend in decrease of blood pressure in all groups, the decrease reached significant significance in systolic blood pressure in group 1 and diastolic blood pressure in group 3. Finally, except group 2, the tumor size remained unchanged.

Mutation of the GnRHR Proximal Promoter AP-1 Element in Mice Results in Suboptimal GnRH Induction of LH and an Abnormal Reproductive Phenotype

Reproduction is regulated by the gonadotropins, LH and FSH, which are synthesized and secreted by pituitary gonadotrophs in response to hypothalamic GnRH in a pulse frequency dependent manner. The gonadotroph decodes GnRH pulsatility via the GnRH receptor (GnRHR), which increases in expression and cell surface density before estrus and is responsible for downstream signaling cascades that differentially favor gonadotropin expression. The gonadotroph Gnrhr promoter contains a tripartite enhancer, including an AP-1 element that is necessary for full GnRH induction of Gnrhr expression in vitro. We previously generated an AP-1 knock-in (KI) mouse model with a single point mutation (C-269T) in the Gnrhr promoter AP-1 binding motif that resulted in an abnormal reproductive phenotype in female mice. Compared to wildtype (WT) littermates, female KI mice had a significant delay in first estrus, disrupted estrous cyclicity, fewer corpora lutea, and smaller litters. Males had no apparent reproductive phenotype. Basal serum gonadotropin levels were similar between WT and KI mice, but gonadectomy induced a significantly lower rise in serum LH levels of KI mice relative to WT mice, concomitant with significantly lower pituitary Gnrhr, Lhb, and Fshb mRNA levels in both sexes. We have now extended the characterization of these mice by measuring LH pulsatility and assessing GnRH induction of LH in vivo and in vitro. The frequency and amplitude of LH pulses over three hours were similar in ovariectomized WT and KI mice; however, KI mice had significantly reduced LH secretion, as measured by area under the curve. Similarly, GnRH treatment induced a diminished LH response in intact KI compared to WT males. In vitro cultures of hemi-pituitaries from gonadectomized WT and KI males were exposed to 0.01 nM GnRH and LH secretion into culture media was measured by ELISA at 0, 0.5, 1, 2, and 4 hours. There was no difference in basal LH secretion between WT and KI pituitaries but GnRH induction of LH was significantly lower in cultures from AP-1 mutant mice, indicating a direct impairment of GnRH action at the level of the pituitary. Taken together, these data indicate that the gonadotroph Gnrhr AP-1 promoter motif is critical for normal reproductive function. Prevention of AP-1 binding to the Gnrhr proximal promoter element decreases GnRH-induced Gnrhr, Lhb, and Fshb levels, impairs GnRH-stimulated LH secretion, and disrupts pubertal development and reproductive cyclicity in female mice.

Effect of Experimentally Induced Sleep Fragmentation and Hypoestrogenism on Fasting Nutrient Utilization in Pre-Menopausal Women

Background: Both sleep disturbance and menopause have independently been associated with weight gain in women. Possible mechanisms contributing to this weight gain may be changes in resting energy expenditure (REE) and/or nutrient utilization. Therefore, in the current study we aimed to examine the effects of experimentally induced sleep fragmentation and pharmacologic estradiol (E2) withdrawal on REE and nutrient utilization in the fasted state. Design: We studied pre-menopausal women during 5-night inpatient studies repeated in the mid-to-late follicular phase (high-E2; n=21) and following leuprolide-induced hypoestrogenism (low-E2; n=9 completed second visit). During each admission there were two nights of unfragmented sleep [8-h time in bed (TIB)] and three nights of fragmented sleep [9-h TIB]. Sleep was fragmented using an auditory stimulus delivered every 15 minutes that sustained wake for 2 minutes, producing 1 hour of wake after sleep onset. Study diets consisted of 3 meals and a snack each day and were iso-caloric across the two visits. REE and nutrient utilization were assessed in the fasted state via indirect calorimetry and compared between E2 states following unfragmented and fragmented sleep using linear mixed models. Results: Sleep fragmentation in the high-E2 state increased the respiratory quotient (RQ; +3%; p=0.03) with an accompanying increase in carbohydrate oxidation (+20%; p=0.02) and decrease in fat oxidation (-16%; p=0.03). The same effect was observed in response to E2-withdrawl during unfragmented sleep [increased RQ (+5%; p=0.01) and carbohydrate oxidation (+33%; p=0.01), and decreased fat oxidation (-26%; p=0.01)]. There was no additive effect of sleep fragmentation on nutrient utilization in the low-E2 state suggesting a possible ceiling (RQ and carbohydrate oxidation) and floor (fat oxidation) effect. There was no effect of sleep fragmentation or E2 state on REE. Conclusion: Both sleep fragmentation and hypoestrogenism were shown to alter fasting nutrient utilization, but not REE, in a manner that may contribute to weight gain in menopausal women. These findings are important for understanding weight gain during menopause, which is characterized by estrogen withdrawal and often accompanied by sleep disturbances.

Genotype-Phenotype Correlations in Central Precocious Puberty Caused by MKRN3 Mutations

CONTEXT

Loss-of-function mutations of makorin RING finger protein 3 (MKRN3) are the most common monogenic cause of familial central precocious puberty (CPP).

OBJECTIVE

To describe the clinical and hormonal features of a large cohort of patients with CPP due to MKRN3 mutations and compare the characteristics of different types of genetic defects.

METHODS

Multiethnic cohort of 716 patients with familial or idiopathic CPP screened for MKRN3 mutations using Sanger sequencing. A group of 156 Brazilian girls with idiopathic CPP (ICPP) was used as control group.

RESULTS

Seventy-one patients (45 girls and 26 boys from 36 families) had 18 different loss-of-function MKRN3 mutations. Eight mutations were classified as severe (70% of patients). Among the 71 patients, first pubertal signs occurred at 6.2 ± 1.2 years in girls and 7.1 ± 1.5 years in boys. Girls with MKRN3 mutations had a shorter delay between puberty onset and first evaluation and higher follicle-stimulating hormone levels than ICPP. Patients with severe MKRN3 mutations had a greater bone age advancement than patients with missense mutations (2.3 ± 1.6 vs 1.6 ± 1.4 years, P = .048), and had higher basal luteinizing hormone levels (2.2 ± 1.8 vs 1.1 ± 1.1 UI/L, P = .018) at the time of presentation. Computational protein modeling revealed that 60% of the missense mutations were predicted to cause protein destabilization.

CONCLUSION

Inherited premature activation of the reproductive axis caused by loss-of-function mutations of MKRN3 is clinically indistinct from ICPP. However, the type of genetic defect may affect bone age maturation and gonadotropin levels.

Body Habitus Across the Lifespan and Risk of Pituitary Adenoma

CONTEXT

No studies have examined the association between body habitus and incidence of pituitary adenoma.

OBJECTIVE

To determine if body mass index (BMI), waist circumference, body somatotype, or height are associated with risk of pituitary adenoma.

DESIGN

Pooled analysis of 3 prospective cohort studies.

SETTING

Population-based study.

PARTICIPANTS

Participants of the Nurses' Health Study (NHS), Nurses' Health Study II (NHSII), and the Health Professionals Follow-Up Study (HPFS), totaling 284 946 American health professionals.

EXPOSURES

BMI, waist circumference, body somatotype, and height.

OUTCOME MEASURES

Self-reported incident pituitary adenoma. Multivariable (MV)-adjusted hazard ratios (HRs) of pituitary adenoma were estimated using Cox proportional hazards models.

RESULTS

During 7 350 156 person-years of follow-up, 387 incident pituitary adenomas were reported. Comparing BMI of ≥30 to <25 kg/m2, higher adult BMI was associated with higher risk of pituitary adenoma (MV HR = 1.74; 95% CI, 1.33-2.28), as was higher maximum adult BMI (MV HR = 1.76; 95% CI, 1.34-2.30), higher waist circumference (MV HR = 1.06; 95% CI, 1.04-1.09 per inch), and higher BMI during early adulthood (at age 18 to 21, MV HR = 2.65; 95% CI, 1.56-4.49). Taller adult height was associated with pituitary adenoma (MV HR = 1.05; 95% CI, 1.01-1.09 per inch). Overall findings were similar in women and men, although power was limited in men (n = 62 cases). Sensitivity analyses demonstrated that the association between adult BMI and pituitary adenoma extended to at least 14 years prior to diagnosis and that the results were not affected when analyses were restricted to participants with similar healthcare utilization.

CONCLUSION

Higher BMI and waist circumference, from early adulthood to the time of diagnosis, were associated with higher risk of pituitary adenoma.

Plasma androgens and the presence and course of depression in a large cohort of women

Major depressive disorder (MDD) has a higher prevalence in women with supraphysiologic androgen levels. Whether there is also an association between depression and androgen levels in the physiological range, is unknown. This study examined if women with current MDD have higher androgen levels compared to women who have never had MDD, and if androgen levels are associated with onset and remission of MDD. In 1659 women (513 current MDD, 754 remitted MDD, and 392 never MDD), baseline plasma levels of total testosterone, 5α-dihydrotestosterone, and androstenedione were determined with liquid chromatography-tandem mass spectrometry, and dehydroepiandrosterone-sulfate and sex hormone binding globulin (SHBG) with radioimmunoassays. Free testosterone was calculated. MDD status was assessed at baseline, and at 2 and 4 years follow-up. Women were aged between 18 and 65 years (mean age 41) with total testosterone levels in the physiological range (geometric mean 0.72 nmol/L [95% CI 0.27-1.93]). After adjusting for covariates and multiple testing, women with current MDD had a higher mean free testosterone than women who never had MDD (adjusted geometric mean 8.50 vs. 7.55 pmol/L, p = 0.0005), but this difference was not large enough to be considered clinically meaningful as it was consistent with statistical equivalence. Levels of other androgens and SHBG did not differ and were also statistically equivalent between the groups. None of the androgens or SHBG levels predicted onset or remission of MDD. Our findings support the idea that plasma androgens within the physiological range have no or only limited effects on depressive disorders in women.

Postoperative Day 1 Morning Cortisol Value as a Biomarker to Predict Long-term Remission of Cushing Disease

CONTEXT

Recurrence of Cushing disease (CD) can occur even decades after surgery. Biomarkers to predict recurrence of CD after surgery have been studied but are inconclusive.

OBJECTIVE

The aim of our study was to identify specific biomarkers that can predict long-term remission after neurosurgery.

DESIGN

Identification of specific biomarkers to predict long-term remission of CD was performed by logistic regression analysis followed by Kaplan-Meier survival analysis, using recurrence as the dependent variable.

SETTING

A total of 260 patients with CD identified from our institutional research patient data registry search tool and from patients who presented to our longitudinal multidisciplinary clinic between May 2008 and May 2018 underwent statistical analysis.

INTERVENTIONS

Data on clinical features, neuro-imaging study, pathology, biochemistry, and treatments were collected by reviewing digital chart records.

MAIN OUTCOME MEASURE

Postoperative cortisol as a biomarker to predict long-term remission after surgical treatment for CD.

RESULTS

By logistic regression analysis, postoperative day 1 (POD1) morning (5-10 am) serum cortisol, female sex, and proliferative index had significant association with CD recurrence (odds ratio [OR] = 1.025, 95% CI: 1.002-1.048, P = .032). In contrast, the postoperative nadir cortisol (OR = 1.081, 95% CI: 0.989-1.181, P = .086), urinary free cortisol (OR = 1.032, 95% CI: 0.994-1.07, P = .098), and late night salivary cortisol (OR = 1.383, 95% CI: 0.841-2.274, P = .201) had no significant correlation with recurrence. A significant association between POD1 morning serum cortisol and long-term CD remission was verified by Kaplan-Meier analysis when using POD1 morning serum cortisol <5 μg/dL as the cut-off.

CONCLUSIONS

The POD1 morning serum cortisol level has a significant association with CD recurrence.

Puberty, A Sensitive Window of Hypothalamic Development and Plasticity

Puberty is a developmental period characterized by a broad range of physiologic changes necessary for the acquisition of adult sexual and reproductive maturity. These changes mirror complex modifications within the central nervous system, including within the hypothalamus. These modifications result in the maturation of a fully active hypothalamic-pituitary-gonadal (HPG) axis, the neuroendocrine cascade ensuring gonadal activation, sex steroid secretion, and gametogenesis. A complex and finely regulated neural network overseeing the HPG axis, particularly the pubertal reactivation of gonadotropin-releasing hormone (GnRH) secretion, has been progressively unveiled in the last 3 decades. This network includes kisspeptin, neurokinin B, GABAergic, and glutamatergic neurons as well as glial cells. In addition to substantial modifications in the expression of key targets, several changes in neuronal morphology, neural connections, and synapse organization occur to establish mature and coordinated neurohormonal secretion, leading to puberty initiation. The aim of this review is to outline the current knowledge of the major changes that neurons secreting GnRH and their neuronal and glial partners undergo before and after puberty. Emerging mediators upstream of GnRH, uncovered in recent years, are also addressed herein. In addition, the effects of sex steroids, particularly estradiol, on changes in hypothalamic neurodevelopment and plasticity are discussed.

Effects of growth hormone receptor antagonism and somatostatin analog administration on quality of life in acromegaly

OBJECTIVE

Acromegaly is associated with impaired quality of life (QoL). We investigated the effects of biochemical control of acromegaly by growth hormone receptor antagonism vs somatostatin analog therapy on QoL.

DESIGN

Cross-sectional.

PATIENTS

116 subjects: n = 55 receiving a somatostatin analog (SSA group); n = 29 receiving pegvisomant (PEG group); n = 32 active acromegaly on no medical therapy (ACTIVE group).

MEASUREMENTS

Acromegaly QoL Questionnaire (AcroQoL), Rand 36-Item Short Form Survey (SF-36) and Gastrointestinal QoL Index (GIQLI); fasting glucose, insulin and IGF-1 levels (LC/MS, Quest Diagnostics).

RESULTS

There were no group differences in mean age, BMI or sex [(whole cohort mean ± SD) age 52 ± 14 years, BMI 30 ± 6 kg/m² , and male sex 38%]. Mean IGF-1 Z-scores were higher in ACTIVE (3.9 ± 1.0) vs SSA and PEG, which did not differ from one another (0.5 ± 0.7 and 0.5 ± 0.7, P < .0001 vs ACTIVE). Eighty-three per cent of PEG previously received somatostatin analogs, which had been discontinued due to lack of efficacy (52%) or side effects (41%). There were no differences in the four QoL primary end-points (AcroQoL Global Score, SF-36 Physical Component Summary Score, SF-36 Mental Health Summary Score and GIQLI Global Score) between SSA and PEG. Higher HbA1c, BMI and IGF-1 Z-scores were associated with poorer QoL in several domains.

CONCLUSION

Our data support a comparable QoL in patients receiving pegvisomant vs somatostatin analogs, despite the fact that the vast majority receiving pegvisomant did not respond to or were not able to tolerate somatostatin analogs.

Makorin RING finger protein 3 and central precocious puberty

Makorin RING finger protein 3 (MKRN3) is a key inhibitor of the hypothalamic-pituitary-gonadal axis. Loss-of-function mutations in MKRN3 cause familial and sporadic central precocious puberty (CPP), while polymorphisms are associated with age at menarche. To date, 115 patients with CPP carrying MKRN3 mutations have been described, harboring 48 different genetic variants. The prevalence of MKRN3 mutations in genetically screened populations with CPP is estimated at 9.0%. Girls are more commonly and more seriously affected than boys. MKRN3 is expressed in humans and rodents in the central nervous system. Circulating levels in humans and hypothalamic expression in rodents decrease during pubertal progression. Although some MKRN3 regulators have been identified, the precise mechanism by which MKRN3 inhibits the hypothalamic-pituitary-gonadal axis remains elusive. The role of makorins in developmental physiology and organ differentiation and the role of maternal imprinting are discussed herein.

GENETICS IN ENDOCRINOLOGY: Genetic etiologies of central precocious puberty and the role of imprinted genes

Pubertal timing is regulated by the complex interplay of genetic, environmental, nutritional and epigenetic factors. Criteria for determining normal pubertal timing, and thus the definition of precocious puberty, have evolved based on published population studies. The significance of the genetic influence on pubertal timing is supported by familial pubertal timing and twin studies. In contrast to the many monogenic causes associated with hypogonadotropic hypogonadism, only four monogenic causes of central precocious puberty (CPP) have been described. Loss-of-function mutations in Makorin Ring Finger Protein 3(MKRN3), a maternally imprinted gene on chromosome 15 within the Prader-Willi syndrome locus, are the most common identified genetic cause of CPP. More recently, several mutations in a second maternally imprinted gene, Delta-like noncanonical Notch ligand 1 (DLK1), have also been associated with CPP. Polymorphisms in both genes have also been associated with the age of menarche in genome-wide association studies. Mutations in the genes encoding kisspeptin (KISS1) and its receptor (KISS1R), potent activators of GnRH secretion, have also been described in association with CPP, but remain rare monogenic causes. CPP has both short- and long-term health implications for children, highlighting the importance of understanding the mechanisms contributing to early puberty. Additionally, given the role of mutations in the imprinted genes MKRN3 and DLK1 in pubertal timing, other imprinted candidate genes should be considered for a role in puberty initiation.