Spontaneous growth hormone secretion increases during puberty in normal girls and boys

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.

Siblings reduce multiple sclerosis risk by preventing delayed primary Epstein-Barr virus infection

Epstein-Barr virus infection, and perhaps almost exclusively delayed Epstein-Barr virus infection, seems to be a prerequisite for the development of multiple sclerosis. Siblings provide protection against infectious mononucleosis by occasionally preventing delayed primary Epstein-Barr virus infection, with its associated high risk of infectious mononucleosis. Each additional sibling provides further protection according to the age difference between the index child and the sibling. The closer the siblings are in age, the higher the protection, with younger siblings being more protective against infectious mononucleosis than older siblings. If the hypothesis that delayed Epstein-Barr virus infection is necessary for the development of multiple sclerosis is true, then the relative risk of multiple sclerosis as a function of sibship constellation should mirror the relative risk of infectious mononucleosis as a function of sibship constellation. Such an indirect hypothesis test is necessitated by the fact that age at primary Epstein-Barr virus infection is unknown for practically all people who have not experienced infectious mononucleosis. In this retrospective cohort study using nationwide registers, we followed all Danes born during the period 1971-2018 (n = 2 576 011) from 1977 to 2018 for hospital contacts with an infectious mononucleosis diagnosis (n = 23 905) or a multiple sclerosis diagnosis (n = 4442), defining two different end points. Relative risks (hazard ratios) of each end point as a function of sibship constellation were obtained from stratified Cox regression analyses. The hazard ratios of interest for infectious mononucleosis and multiple sclerosis could be assumed to be identical (test for homogeneity P = 0.19), implying that having siblings, especially of younger age, may protect a person against multiple sclerosis through early exposure to the Epstein-Barr virus. Maximum protection per sibling was obtained by having a 0-2 years younger sibling, corresponding to a hazard ratio of 0.80, with a 95% confidence interval of 0.76-0.85. The corresponding hazard ratio from having an (0-2 years) older sibling was 0.91 (0.86-0.96). Our results suggest that it may be possible essentially to eradicate multiple sclerosis using an Epstein-Barr virus vaccine administered before the teenage years. Getting there would require both successful replication of our study findings and, if so, elucidation of why early Epstein-Barr virus infection does not usually trigger the immune mechanisms responsible for the association between delayed Epstein-Barr virus infection and multiple sclerosis risk.

Quantitative proteomics analysis to assess protein expression levels in the ovaries of pubescent goats

Background

Changes in the abundance of ovarian proteins play a key role in the regulation of reproduction. However, to date, no studies have investigated such changes in pubescent goats. Herein we applied isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography–tandem mass spectrometry to analyze the expression levels of ovarian proteins in pre-pubertal (n = 3) and pubertal (n = 3) goats.

Results

Overall, 7,550 proteins were recognized; 301 (176 up- and 125 downregulated) were identified as differentially abundant proteins (DAPs). Five DAPs were randomly selected for expression level validation by Western blotting; the results of Western blotting and iTRAQ analysis were consistent. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that DAPs were enriched in olfactory transduction, glutathione metabolism, and calcium signaling pathways. Besides, gene ontology functional enrichment analysis revealed that several DAPs enriched in biological processes were associated with cellular process, biological regulation, metabolic process, and response to stimulus. Protein–protein interaction network showed that proteins interacting with CDK1, HSPA1A, and UCK2 were the most abundant.

Conclusions

We identified 301 DAPs, which were enriched in olfactory transduction, glutathione metabolism, and calcium signaling pathways, suggesting the involvement of these processes in the onset of puberty. Further studies are warranted to more comprehensively explore the function of the identified DAPs and aforementioned signaling pathways to gain novel, deeper insights into the mechanisms underlying the onset of puberty.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08699-y.

Cell Networks in Endocrine/Neuroendocrine Gland Function

Reproduction, growth, stress, and metabolism are determined by endocrine/neuroendocrine systems that regulate circulating hormone concentrations. All these systems generate rhythms and changes in hormone pulsatility observed in a variety of pathophysiological states. Thus, the output of endocrine/neuroendocrine systems must be regulated within a narrow window of effective hormone concentrations but must also maintain a capacity for plasticity to respond to changing physiological demands. Remarkably most endocrinologists still have a "textbook" view of endocrine gland organization which has emanated from 20^th century histological studies on thin 2D tissue sections. However, 21^st -century technological advances, including in-depth 3D imaging of specific cell types have vastly changed our knowledge. We now know that various levels of multicellular organization can be found across different glands, that organizational motifs can vary between species and can be modified to enhance or decrease hormonal release. This article focuses on how the organization of cells regulates hormone output using three endocrine/neuroendocrine glands that present different levels of organization and complexity: the adrenal medulla, with a single neuroendocrine cell type; the anterior pituitary, with multiple intermingled cell types; and the pancreas with multiple intermingled cell types organized into distinct functional units. We give an overview of recent methodologies that allow the study of the different components within endocrine systems, particularly their temporal and spatial relationships. We believe the emerging findings about network organization, and its impact on hormone secretion, are crucial to understanding how homeostatic regulation of endocrine axes is carried out within endocrine organs themselves. © 2022 American Physiological Society. Compr Physiol 12:3371-3415, 2022.

Evaluation of Weight Gain, Clinicopathological and Radiographic Changes after Early Diagnosis and Treatment of Congenital Hypothyroidism in Cats

Congenital hypothyroidism is uncommon in cats. This case report describes weight gain, clinicopathological and radiographic changes after early diagnosis and treatment of congenital hypothyroidism in three British shorthair cats’ siblings. Data were assessed at 53 (diagnosis), 83, 185 and 365 days of age. Correlations between serum insulin-like growth factor-1 (IGF-1) and body weight, levothyroxine dose, total thyroxine, and thyroid-stimulating hormone concentrations were evaluated. The body weights of the congenital hypothyroid kittens were compared with those of their two healthy siblings and British shorthair kittens of the same age. At diagnosis, the congenital hypothyroid kittens showed a significantly lower body weight compared to the healthy siblings (p = 0.03). After diagnosis, oral levothyroxine supplementation was started. The difference in body weight was no longer observed after one month of treatment. The clinical signs, clinicopathological and radiographic abnormalities ameliorated after one month of treatment. IGF-1 concentration was significantly positively correlated with body weight (rs = 0.80, p < 0.002). In conclusion, resolution of the clinical signs, achieving a consistent within-breed weight, and improvement of the clinicopathological and radiographic parameters demonstrated the importance of the early diagnosis and treatment of feline congenital hypothyroidism.

Differential Diagnosis of the Short IGF-I-Deficient Child with Apparently Normal Growth Hormone Secretion

The current differential diagnosis for a short child with low insulin-like growth factor I (IGF-I) and a normal growth hormone (GH) peak in a GH stimulation test (GHST), after exclusion of acquired causes, includes the following disorders: (1) a decreased spontaneous GH secretion in contrast to a normal stimulated GH peak ("GH neurosecretory dysfunction," GHND) and (2) genetic conditions with a normal GH sensitivity (e.g., pathogenic variants of GH1 or GHSR) and (3) GH insensitivity (GHI). We present a critical appraisal of the concept of GHND and the role of 12- or 24-h GH profiles in the selection of children for GH treatment. The mean 24-h GH concentration in healthy children overlaps with that in those with GH deficiency, indicating that the previously proposed cutoff limit (3.0-3.2 μg/L) is too high. The main advantage of performing a GH profile is that it prevents about 20% of false-positive test results of the GHST, while it also detects a low spontaneous GH secretion in children who would be considered GH sufficient based on a stimulation test. However, due to a considerable burden for patients and the health budget, GH profiles are only used in few centres. Regarding genetic causes, there is good evidence of the existence of Kowarski syndrome (due to GH1 variants) but less on the role of GHSR variants. Several genetic causes of (partial) GHI are known (GHR, STAT5B, STAT3, IGF1, IGFALS defects, and Noonan and 3M syndromes), some responding positively to GH therapy. In the final section, we speculate on hypothetical causes.

Growth Hormone Stimulation Testing: To Test or Not to Test? That Is One of the Questions

The evaluation of children with short stature includes monitoring over a prolonged period to establish a growth pattern as well as the exclusion of chronic medical conditions that affect growth. After a period of monitoring, evaluation, and screening, growth hormone stimulation testing is considered when the diagnosis of growth hormone deficiency (GHD) is entertained. Though flawed, growth hormone stimulation tests remain part of the comprehensive evaluation of growth and are essential for the diagnosis of growth hormone (GH) deficiency. Variables including testing length, growth hormone assay and diagnostic cut off affect results. Beyond the intrinsic issues of testing, results of GH stimulation testing can be influenced by patient characteristics. Various factors including age, gender, puberty, nutritional status and body weight modulate the secretion of GH.

Growth, growth potential, and influences on adult height in the transgender and gender-diverse population

The sexually dimorphic trait of height is one aspect of the experience of transgender and gender‐diverse (TGD) individuals that may influence their gender dysphoria and satisfaction with their transition. In this article, we have reviewed the current knowledge of the factors that contribute to one's final adult height and how it might be affected in TGD youth who have not experienced their gonadal puberty in the setting of receiving gonadotropin‐releasing hormone analog (GnRHa) and gender‐affirming hormonal treatment. Additional research is needed to characterize the influence of growth and final adult height on the lived experience of TGD youth and adults and how to best assess their growth, predict their final adult height, and how medical transition can be potentially modified to help them meet their goals.

Differential effects of androgens and estrogens over cellular GH sensitivity in HEPG2 cells

Testosterone and estrogen concentrations progressively increase during puberty, and in association with growth hormone (GH), lead to the increase in height velocity known as the pubertal growth spurt. Very limited information is available however, regarding the possible effects of sex steroids over GH cellular sensitivity.

OBJECTIVE

To investigate the effects of different concentrations of testosterone, estradiol and dihydrotestosterone over the GH intracellular signaling pathway.

METHODS

We evaluated the effects of these sex steroids on the nuclear phosphorylation of STAT5b and IGF-1 expression, in HEPG2 human hepatoma cells. In addition, we studied whether Tamoxifen (TAM), can modulate these effects.

RESULTS

The highest concentration of T tested (10 ng/mL) co-incubated with a fixed concentration of GH (40 ng/mL) increased nuclear STAT5b phosphorylation compared with GH alone (1.34 ± 0.2 vs 0.6 ± 0.09 AU; *p < 0.05), as well as IGF-1 expression (0.6 ± 0.03 vs 0.32 ± 0.05 AU; *p < 0.05). This effect was not observed with lower concentrations of T tested (1 and 5 ng/mL). A similar increase in nuclear STAT5b phosphorylation was observed with the lowest concentration of E₂ tested (20 pg/mL), co-incubated with the same fixed concentration of GH (3.6 ± 0.5 vs 1.28 ± 0.33 AU; *p < 0.05). This effect was also associated with an increase in IGF-1 expression (0.73 ± 0.02 vs 0.39 ± 0.04 AU; *p < 0.05). These results were not observed with higher concentrations of E₂ tested (75 and 200 pg/mL). DHT at concentrations of 0.1, 0.25 and 0.5 ng/mL, co-stimulated with GH, did not change cytoplasmic STAT5b phosphorylation, nuclear STAT5b or IGF-1 expression. In addition, the co-incubation of TAM with the highest concentration of T tested (10 ng/mL) and GH (40 ng/mL) did not change cytoplasmic, nuclear pSTAT5 levels or IGF-1 expression.

CONCLUSIONS

T and E₂ potentiate the GH signaling pathway in a concentration-dependent fashion. The observation that the non-aromatizable androgen dihydrotestosterone does not stimulate this pathway, and that the effects of T are blocked with TAM, suggests that the effects of T over the GH signaling pathway appear to be mediated by estrogen.

Insights from the clinical phenotype of subjects with Laron syndrome in Ecuador

The Ecuadorian cohort of subjects with LS has taught us valuable lessons since the late 80's. We have learned about migration of Sephardic Jews to our country, their isolation in remote hamlets and further inbreeding. These geographical, historical and social determinants induced dissemination of a growth hormone (GH) receptor mutation which widely occurred in those almost inaccessible villages. Consequently, the world's largest Laron syndrome (LS) cohort emerged in Loja and El Oro, two of the southern provinces of Ecuador. We have been fortunate to study these patients since 1987. New clinical features derived from GH insensitivity, their growth patterns as well as treatment with exogenous insulin-like growth factor I (IGF-I) have been reported. Novel biochemical characteristics in the field of GH insensitivity, IGFs, IGF binding proteins (BP) and their clinical correlates have also been described. In the last few years, studies on the morbidity and mortality of Ecuadorian LS adults surprisingly demonstrated that despite obesity, they had lower incidence of diabetes and cancer than their relatives. These events were linked to their metabolic phenotype of elevated but ineffective GH concentrations and low circulating IGF-I and IGFBP-3. It was also noted that absent GH counter-regulation induces a decrease in insulin resistance (IR), which results in low but highly efficient insulin levels which properly handle metabolic substrates. We propose that the combination of low IGF-I signaling, decreased IR, and efficient serum insulin concentrations are reasonable explanations for the diminished incidence of diabetes and cancer in these subjects.

Pituitary Remodeling Throughout Life: Are Resident Stem Cells Involved?

The pituitary gland has the primordial ability to dynamically adapt its cell composition to changing hormonal needs of the organism throughout life. During the first weeks after birth, an impressive growth and maturation phase is occurring in the gland during which the distinct hormonal cell populations expand. During pubertal growth and development, growth hormone (GH) levels need to peak which requires an adaptive enterprise in the GH-producing somatotrope population. At aging, pituitary function wanes which is associated with organismal decay including the somatopause in which GH levels drop. In addition to these key time points of life, the pituitary's endocrine cell landscape plastically adapts during specific (patho-)physiological conditions such as lactation (need for PRL) and stress (engagement of ACTH). Particular resilience is witnessed after physical injury in the (murine) gland, culminating in regeneration of destroyed cell populations. In many other tissues, adaptive and regenerative processes involve the local stem cells. Over the last 15 years, evidence has accumulated that the pituitary gland houses a resident stem cell compartment. Recent studies propose their involvement in at least some of the cell remodeling processes that occur in the postnatal pituitary but support is still fragmentary and not unequivocal. Many questions remain unsolved such as whether the stem cells are key players in the vivid neonatal growth phase and whether the decline in pituitary function at old age is associated with decreased stem cell fitness. Furthermore, the underlying molecular mechanisms of pituitary plasticity, in particular the stem cell-linked ones, are still largely unknown. Pituitary research heavily relies on transgenic in vivo mouse models. While having proven their value, answers to pituitary stem cell-focused questions may more diligently come from a novel powerful in vitro research model, termed organoids, which grow from pituitary stem cells and recapitulate stem cell phenotype and activation status. In this review, we describe pituitary plasticity conditions and summarize what is known on the involvement and phenotype of pituitary stem cells during these pituitary remodeling events.

Association between triglyceride glucose index and peak growth hormone in children with short stature

Growth hormone (GH) secretion is related to many factors, such as weight and puberty, and the reproducibility of GH provocation tests is very poor. This study aimed to evaluate whether the triglyceride (TyG) index was associated with peak GH in children with short stature. This study included 1095 children with short stature divided into two groups based on peak GH level in GH provocation tests [GH deficiency (GHD) group = 733 children; non-GHD group = 362 children]. We found that the TyG index was significantly higher in the GHD group than in the non-GHD group (P < 0.001). A nonlinear relationship was detected between the TyG index and peak GH, whose point was 7.8. A significant negative association between the TyG index and peak GH was observed when the TyG index was greater than 7.8 (β − 2.61, 95% CI − 3.98, − 1.24; P < 0.001), whereas, the relationship between the TyG index and peak GH was not significant when the TyG index was lower than 7.8 (β 0.25, 95% CI − 1.68, 2.17; P = 0.799). There is a nonlinear relationship between the TyG index and peak GH, and a higher TyG index is associated with decreased peak GH in children with short stature.

GH Deficiency and Replacement Therapy in Hypopituitarism: Insight Into the Relationships With Other Hypothalamic-Pituitary Axes

GH deficiency (GHD) in adult patients is a complex condition, mainly due to organic lesion of hypothalamic-pituitary region and often associated with multiple pituitary hormone deficiencies (MPHD). The relationships between the GH/IGF-I system and other hypothalamic-pituitary axes are complicated and not yet fully clarified. Many reports have shown a bidirectional interplay both at a central and at a peripheral level. Signs and symptoms of other pituitary deficiencies often overlap and confuse with those due to GH deficiency. Furthermore, a condition of untreated GHD may mask concomitant pituitary deficiencies, mainly central hypothyroidism and hypoadrenalism. In this setting, the diagnosis could be delayed and possible only after recombinant human Growth Hormone (rhGH) replacement. Since inappropriate replacement of other pituitary hormones may exacerbate many manifestations of GHD, a correct diagnosis is crucial. This paper will focus on the main studies aimed to clarify the effects of GHD and rhGH replacement on other pituitary axes. Elucidating the possible contexts in which GHD may develop and examining the proposed mechanisms at the basis of interactions between the GH/IGF-I system and other axes, we will focus on the importance of a correct diagnosis to avoid possible pitfalls.

Somatotropic-Testicular Axis: A crosstalk between GH/IGF-I and gonadal hormones during development, transition, and adult age

BACKGROUND

The hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-somatotropic (HPS) axes are strongly interconnected. Interactions between these axes are complex and poorly understood. These interactions are characterized by redundancies in reciprocal influences at each level of regulation and the combination of endocrine and paracrine effects that change during development.

OBJECTIVES

To comprehensively review the crosstalk between the HPG and HPS axes and related pathological and clinical aspects during various life stages of male subjects.

MATERIALS AND METHODS

A thorough search of publications available in PubMed was performed using proper keywords.

RESULTS

Molecular studies confirmed the expressions of growth hormone (GH) and insulin-like growth factor-I (IGF-I) receptors on the HPG axis and reproductive organs, indicating a possible interaction between HPS and HPG axes at various levels. Insulin growth factors participate in sexual differentiation during fetal development, indicating that normal HPS axis activity is required for proper testicular development. IGF-I contributes to correct testicular position during minipuberty, determines linear growth during childhood, and promotes puberty onset and pace through gonadotropin-releasing hormone activation. IGF-I levels are high during transition age, even when linear growth is almost complete, suggesting its role in reproductive tract maturation. Patients with GH deficiency (GHD) and insensitivity (GHI) exhibit delayed puberty and impaired genital development; replacement therapy in such patients induces proper pubertal development. In adults, few studies have suggested that lower IGF-I levels are associated with impaired sperm parameters.

DISCUSSION AND CONCLUSION

The role of GH-IGF-I in testicular development remains largely unexplored. However, it is important to evaluate gonadic development in children with GHD. Additionally, HPS axis function should be evaluated in children with urogenital malformation or gonadal development alterations. Correct diagnosis and prompt therapeutic intervention are needed for healthy puberty, attainment of complete gonadal development during transition age, and fertility potential in adulthood.

Discordance Between Stimulated and Spontaneous Growth Hormone Levels in Short Children Is Dependent on Cut-Off Level and Partly Explained by Refractoriness

BACKGROUND

A growth hormone (GH) stimulation test is the recommended method for evaluating GH levels in children with possible GH deficiency (GHD). However, serial measurements of nocturnal spontaneous GH secretion are also performed. Divergent results from these tests have been reported, but with variable frequencies.

OBJECTIVES

To investigate whether performing one or two GH tests is associated with the probability to diagnose a child with GHD; the frequency of divergent results in the arginine-insulin tolerance test (AITT) and the nocturnal spontaneous test using different cut-off levels, and whether refractoriness may explain some of the discordance.

METHODS

In a population-based setting, the medical records of all short children evaluated for possible GHD during January 1993-February 2017 were reviewed. Twenty-one patients had been evaluated with one GH test only and 102 children had been evaluated with a spontaneous nocturnal GH test followed immediately by a complete AITT. Divergent results were defined as having a pathological response on only one of the tests when using 3, 5, 7, and 10 µg/L as cut-offs for peak GH on both tests, 1.1 and 3.3 µg/L for mean nocturnal values and receiver operating characteristic curves-derived cut-offs for nocturnal values.

RESULTS

Children evaluated with one test only were more often diagnosed with GHD compared with children evaluated with both tests (48 vs. 19%, p = 0.019). Divergent results were found in 6-42% of the patients, with higher frequencies seen when higher cut-offs were applied. A higher proportion of patients with stimulated peak values ≤ 7 and ≤ 5 µg/L had a spontaneous peak within 2 h before the start of the AITT compared with patients with higher stimulated peak values (68 vs. 45%, p = 0.026, and 77 vs. 48%, p = 0.033, respectively).

CONCLUSIONS

Divergent results between AITT and nocturnal spontaneous secretion are common in short children, dependent on the cut-offs applied and partly due to refractoriness. Performing both tests decreases the risk of over diagnosing GHD in short children.

Pubertal Hormonal Changes and the Autonomic Nervous System: Potential Role in Pediatric Orthostatic Intolerance

Puberty is initiated by hormonal changes in the adolescent body that trigger physical and behavioral changes to reach adult maturation. As these changes occur, some adolescents experience concerning pubertal symptoms that are associated with dysfunction of the autonomic nervous system (ANS). Vasovagal syncope (VVS) and Postural Orthostatic Tachycardia Syndrome (POTS) are common disorders of the ANS associated with puberty that are related to orthostatic intolerance and share similar symptoms. Compared to young males, young females have decreased orthostatic tolerance and a higher incidence of VVS and POTS. As puberty is linked to changes in specific sex and non-sex hormones, and hormonal therapy sometimes improves orthostatic symptoms in female VVS patients, it is possible that pubertal hormones play a role in the increased susceptibility of young females to autonomic dysfunction. The purpose of this paper is to review the key hormonal changes associated with female puberty, their effects on the ANS, and their potential role in predisposing some adolescent females to cardiovascular autonomic dysfunctions such as VVS and POTS. Increases in pubertal hormones such as estrogen, thyroid hormones, growth hormone, insulin, and insulin-like growth factor-1 promote vasodilatation and decrease blood volume. This may be exacerbated by higher levels of progesterone, which suppresses catecholamine secretion and sympathetic outflow. Abnormal heart rate increases in POTS patients may be exacerbated by pubertal increases in leptin, insulin, and thyroid hormones acting to increase sympathetic nervous system activity and/or catecholamine levels. Given the coincidental timing of female pubertal hormone surges and adolescent onset of VVS and POTS in young women, coupled with the known roles of these hormones in modulating cardiovascular homeostasis, it is likely that female pubertal hormones play a role in predisposing females to VVS and POTS during puberty. Further research is necessary to confirm the effects of female pubertal hormones on autonomic function, and their role in pubertal autonomic disorders such as VVS and POTS, in order to inform the treatment and management of these debilitating disorders.

Distribution-free estimation of local growth rates around interval censored anchoring events

Biological processes are usually defined on timelines that are anchored by specific events. For example, cancer growth is typically measured by the change in tumor size from the time of oncogenesis. In the absence of such anchoring events, longitudinal assessments of the outcome lose their temporal reference. In this paper, we considered the estimation of local change rates in the outcomes when the anchoring events are interval-censored. Viewing the subject-specific anchoring event times as random variables from an unspecified distribution, we proposed a distribution-free estimation method for the local growth rates around the unobserved anchoring events. We expressed the rate parameters as stochastic functionals of the anchoring time distribution and showed that under mild regularity conditions, consistent and asymptotically normal estimates of the rate parameters could be achieved, with a n convergence rate. We conducted a carefully designed simulation study to evaluate the finite sample performance of the method. To motivate and illustrate the use of the proposed method, we estimated the skeletal growth rates of male and female adolescents, before and after the unobserved pubertal growth spurt (PGS) times.

Reliability of clonidine testing for the diagnosis of growth hormone deficiency in children and adolescents

OBJECTIVE

The diagnosis of growth hormone deficiency (GHD) is currently based on clinical, auxological, biochemical and neuro-radiological investigation. Provocative tests of GH secretion using physiological/pharmacological stimuli are required to confirm GHD. The clonidine test (CT) is widely used to assess GH secretory status. In this retrospective study, we analyzed the reliability of CT and the effect of puberty in a large number of children with short stature who had been evaluated for suspected GHD.

DESIGN AND PATIENTS

Data were collected retrospectively from 327 children and adolescents with short stature (204 boys and 123 girls, median age 10.5 years (IQR 7.90-12.40) followed in four Italian Paediatric Endocrine Units (Cagliari, Genova, Napoli and Roma) between 2005 and 2013.

MEASUREMENTS

All children underwent CT as the first GH stimulation test after exclusion of other known cause of their short stature.

RESULTS

In 73 prepubertal children and 25 pubertal children, the GH peak after CT was <7 μg/L. GHD was confirmed in 87 (37 organic, 50 idiopathic). Six prepubertal and five pubertal patients showed false positive responses. The median BMI-SDS in these children was similar to that of children with GH peak ≥7 μg/L, and none were obese. Overall, the prevalence of false-positive responses was 3.3%. The median (IQR) peak GH after CT was similar between prepubertal and pubertal GHD (3.80 μg/L [1.7-6.00] vs 3.51 μg/L [0.76-5.74]) and non-GHD (13.70 μg/L [10.70-18.40] vs 12.40 μg/L [9.90-19.25]) children.

CONCLUSIONS

Our results show that CT is a reliable and safe GH-releasing agent in both prepubertal and pubertal children.

Selective Serotonin Reuptake Inhibitors Reduce Longitudinal Growth in Risperidone-Treated Boys

OBJECTIVES

To examine whether selective serotonin reuptake inhibitors (SSRIs) inhibit longitudinal growth in children and adolescents, particularly in the early stages of puberty, using a sample of convenience comprising risperidone-treated boys.

STUDY DESIGN

Data from four clinic-based studies in risperidone-treated 5- to 17-year-old boys with no general medical conditions were combined for this analysis. Anthropometric measurements and psychotropic treatment history were extracted from the medical and pharmacy records. Linear mixed effects regression analyses examined the association between SSRI use and change in age-sex-specific height and body mass index z scores, after adjusting for relevant confounders.

RESULTS

Risperidone-treated boys (n = 267; age: 12.7 ± 2.7 years), 71% of whom had ever taken an SSRI, contributed to the analysis. After adjusting for age, psychostimulant and antipsychotic use, and time in the study, both the duration of SSRI use as well as the cumulative dose were inversely associated with height z score after age 11 years (P < .0001). After adjusting for baseline height, duration of SSRI use was most strongly inversely associated with height z score in Tanner stages 3 and 4 boys who took SSRIs continuously (r = -0.69, P < .009). No association was observed with body mass index z score.

CONCLUSIONS

In risperidone-treated boys, SSRI use is associated with reduced longitudinal growth, particularly in those undergoing puberty. Whether adult height or other metabolic or psychological outcomes are affected remains to be determined.

The Physiology of Childhood Growth: Hormonal Regulation

The growth patterns of a child changes from uterine life until the end of puberty. Height velocity is highest in utero and declines after birth until puberty when it rises again. Important hormonal regulators of childhood growth are growth hormone, insulin-like growth factor 1, sex steroids, and thyroid hormone. This review gives an overview of these hormonal regulators of growth and their interplay with nutrition and other key players such as inflammatory cytokines.

Insulin resistance depends on GH counter-regulation in two syndromes of short stature

Specific phenotypic features of subjects affected with genetic syndromes depend on peculiarities of expression of each discrete mutation and on extent of its divergence from normal physiology. In this context, and when studying the GH/IGF-I axis of subjects with two different syndromes that include severe short stature (SSS), we noticed different metabolic phenotypes in each cohort. Subjects with Laron syndrome (LS), who have GH insensitivity (GHI), display obesity, increased body fat, enhanced insulin sensitivity and diminished incidence of diabetes mellitus. Subjects with a new syndrome (NS), who have normal GH signaling, display intrauterine growth retardation (IUGR), normal to slightly elevated body fat content, insulin resistance and early onset type 2 diabetes mellitus (T2DM). In consequence, we were able to observe the clinical consequences of different GH counter-regulation status on carbohydrate metabolism, especially considering that subjects with either syndrome most likely have diminished pancreatic reserve.

Endocrine rhythms of growth hormone release: Insights from animal studies

Growth hormone (GH) secretory patterns emerge following birth, and changes in patterning occur throughout life. These secretory patterns are coupled to growth, reproduction and metabolism. Comparing human and animal studies, this review will highlight ultradian patterning of GH release and the mechanisms that contribute to this. Discussions will focus on the emergence in variations in the number and frequency of GH secretory events, and the amounts of GH released (peak and basal). Animal studies have contributed significantly to our understanding of the processes that regulate GH release. However, translation of knowledge from animal models to benefit our understanding of human physiology is sometimes limited. To overcome these limitations, it is critical that we reconcile the cause and consequences of differences in GH release between humans and model organisms. In doing so, we can embrace emerging technologies that will rapidly advance our knowledge of endogenous process that control GH release.

Body typing of children and adolescents using 3D-body scanning

Three-dimensional (3D-) body scanning of children and adolescents allows the detailed study of physiological development in terms of anthropometrical alterations which potentially provide early onset markers for obesity. Here, we present a systematic analysis of body scanning data of 2,700 urban children and adolescents in the age range between 5 and 18 years with the special aim to stratify the participants into distinct body shape types and to describe their change upon development. In a first step, we extracted a set of eight representative meta-measures from the data. Each of them collects a related group of anthropometrical features and changes specifically upon aging. In a second step we defined seven body types by clustering the meta-measures of all participants. These body types describe the body shapes in terms of three weight (lower, normal and overweight) and three age (young, medium and older) categories. For younger children (age of 5-10 years) we found a common 'early childhood body shape' which splits into three weight-dependent types for older children, with one or two years delay for boys. Our study shows that the concept of body types provides a reliable option for the anthropometric characterization of developing and aging populations.

Prediction of glycaemic control in young children and adolescents with type 1 diabetes mellitus using mixed-effects logistic regression modelling

OBJECTIVES

Glycaemic control in children and adolescents with type 1 diabetes mellitus can be challenging, complex and influenced by many factors. This study aimed to identify patient characteristics that were predictive of satisfactory glycaemic control in the paediatric population using a logistic regression mixed-effects (population) modelling approach.

METHODS

The data were obtained from 288 patients aged between 1 and 22 years old recorded retrospectively over 3 years (1852 HbA1c observations). HbA1c status was categorised as 'satisfactory' or 'unsatisfactory' glycaemic control, using an a priori cut-off value of HbA1c ≥ 9% (75 mmol/mol), as used routinely by the hospital's endocrine paediatricians. Patients' characteristics were tested as covariates in the model as potential predictors of glycaemic control.

RESULTS

There were three patient characteristics identified as having a significant influence on glycaemic control: HbA1c measurement at the beginning of the observation period (Odds Ratio (OR) = 0.30 per 1% HbA1c increase, 95% confidence interval (CI) = 0.20-0.41); Age (OR = 0.88 per year increase, 95% CI = 0.80-0.94), and fractional disease duration (disease duration/age, OR = 0.80 per 0.10 increase, 95% CI = 0.66-0.93) were collectively identified as factors contributing significantly to lower the probability of satisfactory glycaemic control.

CONCLUSIONS

The study outcomes may prove useful for identifying paediatric patients at risk of having unsatisfactory glycaemic control, and who could require more extensive monitoring, support, or targeted interventions.

Endocrinology, energetics, and human life history: A synthetic model

Human life histories are shaped by the allocation of metabolic energy to competing physiological domains. A model framework of the pathways of energy allocation is described and hormonal regulators of allocation along the pathways of the framework are discussed in the light of evidence from field studies of the endocrinology of human energetics. The framework is then used to generate simple models of two important life history transitions in humans, puberty and the postpartum return to full fecundity in females. The results of the models correspond very closely to observations made in the field.

Osteonecrosis in children with acute lymphoblastic leukemia

The morbidity and toxicity associated with current intensive treatment protocols for acute lymphoblastic leukemia in childhood become even more important as the vast majority of children can be cured and become long-term survivors. Osteonecrosis is one of the most common therapy-related and debilitating side effects of anti-leukemic treatment and can adversely affect long-term quality of life. Incidence and risk factors vary substantially between study groups and therapeutic regimens. We therefore analyzed 22 clinical trials of childhood acute lymphoblastic leukemia in terms of osteonecrosis incidence and risk factors. Adolescent age is the most significant risk factor, with patients >10 years old at the highest risk. Uncritical modification or even significant reduction of glucocorticoid dosage cannot be recommended at this stage. A novel and innovative approach to reduce osteonecrosis-associated morbidity might be systematic early screening for osteonecrosis by serial magnetic resonance images. However, discriminating patients at risk of functional impairment and debilitating progressive joint disease from asymptomatic patients still remains challenging.

Hyperphagia in male melanocortin 4 receptor deficient mice promotes growth independently of growth hormone

KEY POINTS

Loss of function of the melanocortin 4 receptor (MC4R) results in hyperphagia, obesity and increased growth. Despite knowing that MC4Rs control food intake, we are yet to understand why defects in the function of the MC4R receptor contribute to rapid linear growth. We show that hyperphagia following germline loss of MC4R in male mice promotes growth while suppressing the growth hormone-insulin-like growth factor-1 (GH-IGF-1) axis. We propose that hyperinsulinaemia promotes growth while suppressing the GH-IGF-1 axis. It is argued that physiological responses essential to maintain energy flux override conventional mechanisms of pubertal growth to promote the storage of excess energy while ensuring growth.

ABSTRACT

Defects in melanocortin-4-receptor (MC4R) signalling result in hyperphagia, obesity and increased growth. Clinical observations suggest that loss of MC4R function may enhance growth hormone (GH)-mediated growth, although this remains untested. Using male mice with germline loss of the MC4R, we assessed pulsatile GH release and insulin-like growth factor-1 (IGF-1) production and/or release relative to pubertal growth. We demonstrate early-onset suppression of GH release in rapidly growing MC4R deficient (MC4RKO) mice, confirming that increased linear growth in MC4RKO mice does not occur in response to enhanced activation of the GH-IGF-1 axis. The progressive suppression of GH release in MC4RKO mice occurred alongside increased adiposity and the progressive worsening of hyperphagia-associated hyperinsulinaemia. We next prevented hyperphagia in MC4RKO mice through restricting calorie intake in these mice to match that of wild-type (WT) littermates. Pair feeding of MC4RKO mice did not prevent increased adiposity, but attenuated hyperinsulinaemia, recovered GH release, and normalized linear growth rate to that seen in pair-fed WT littermate controls. We conclude that the suppression of GH release in MC4RKO mice occurs independently of increased adipose mass, and is a consequence of hyperphagia-associated hyperinsulinaemia. It is proposed that physiological responses essential to maintain energy flux (hyperinsulinaemia and the suppression of GH release) override conventional mechanisms of pubertal growth to promote the storage of excess energy while ensuring growth. Implications of these findings are likely to extend beyond individuals with defects in MC4R signalling, encompassing physiological changes central to mechanisms of growth and energy homeostasis universal to hyperphagia-associated childhood-onset obesity.

Evaluation of delayed puberty: what diagnostic tests should be performed in the seemingly otherwise well adolescent?

Delayed puberty (DP) is defined as the lack of pubertal development by an age that is 2-2.5 SDs beyond the population mean. Although it generally represents a normal variant in pubertal timing, concern that DP could be the initial presentation of a serious underlying disorder has led to a diagnostic approach that is variable and may include tests that are unnecessary and costly. In this review, we examine available literature regarding the recommended diagnostic tests and aetiologies identified during the evaluation of youth with DP. We view this literature through the prism of the seemingly otherwise well adolescent. To provide further clinical context, we also evaluate the clinical and laboratory data from patients seen with DP in our centre over a 2-year period. The literature and our data reveal wide variability in the number of tests performed and raise the question of whether tests, other than gonadotropins, obtained in the absence of signs or symptoms of an underlying disorder are routinely warranted. Together this information provides a pragmatic rationale for revisiting recommendations calling for broad testing during the initial diagnostic evaluation of an otherwise healthy adolescent with DP. We highlight the need for further research comparing the utility of broader screening with a more streamlined approach, such as limiting initial testing to gonadotropins and a bone age, which, while not diagnostic, is often useful for height prediction, followed by close clinical monitoring. If future research supports a more streamlined approach to DP, then much unnecessary testing could be eliminated.

Prepubertal Adiposity, Vitamin D Status, and Insulin Resistance

OBJECTIVE

To evaluate the following from prepuberty to the puberty-onset: (1) changes in serum 25-hydroxyvitamin-D (25[OH]D), adiposity, and insulin resistance (IR); (2) the effect of prepubertal adiposity on serum 25(OH)D changes; and (3) the combined effect of prepubertal obesity and suboptimal-25(OH)D on IR at puberty-onset.

METHODS

A total of 426 prepubertal children (∼54% girls) were followed during pubertal-onset assessing before and after puberty-onset serum 25(OH)D, adiposity (BMI and waist circumference) and IR indicators (homeostasis-model-assessment of IR [HOMA-IR]). Associations were tested using multiple and logistic regression models adjusted by age, gender, and seasonality.

RESULTS

At puberty-onset, mean serum 25(OH)D decreased (32.2 ± 8.9 Tanner I vs 25.2 ± 8.3 ng/mL Tanner II) and total and central obesity increased (BMI-for-age-z-score ≥2 SD [%]: 16.4 vs 22.1; waist-circumference ≥75th percentile [%]: 27.2 vs 37.1, all P < .05). Children with higher adiposity before puberty onset had higher risk of suboptimal-25(OH)D (<30 ng/mL) in Tanner II (ie, odds ratio = 2.7 [1.1-6.7] for obesity and 2.7 [1.4-5.5] for central-obesity) after adjusting for relevant covariates. Children with higher adiposity and suboptimal-25(OH)D before puberty-onset had higher HOMA-IR compared with their counterparts in Tanner II (HOMA-IR: 2.8 [2.5-3.1] if central-obese and suboptimal-25[OH]D vs 2.1 [1.9-2.3] no central-obesity and optimal-25[OH]D).

CONCLUSIONS

We found that serum 25(OH)D declined with puberty-onset, likely because of adiposity increase. Moreover, children with the combined condition of central-obesity and suboptimal-25(OH)D before puberty-onset had higher pubertal IR. These results highlight the need of ensuring adequate-25(OH)D status before pubertal-onset, particularly in obese children.

An examination of the effects of different doses of recombinant human growth hormone on children with growth hormone deficiency

The aim of the present study was to examine the effects of different doses of recombinant human growth hormone (rhGH) on children with growth hormone deficiency (GHD) and on thyroid and glucose metabolism to identify more reasonable therapeutic doses of growth hormone (GH) for the treatment of this condition. In total, 60 prepubertal patients with GHD were randomly divided into the high-dose and low-dose groups (n=30 per group). The groups were treated with 0.1 or 0.05 U/kg for 6 months, respectively. The follow-up study focused on changes to the serum levels of insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein (IGFBP)-3, blood glucose, thyroid hormone [triiodothyronine (T3) and its prohormone, thyroxine (T4), and thyroid stimulating hormone (TSH)] and the analysis of variance of the repeated data. Changes in the height, body weight and bone age of the high-dose group were greater than those of the low-dose group. After 6 months of treatment, the difference in height between the two groups was statistically significant (P<0.05). Glucose metabolism in the two groups was consistent, but there was a statistically significant difference in the fasting blood glucose (FBG) levels of the two groups after 6 months of treatment (P<0.05). Prior to treatment, the T3, T4 and TSH values (the thyroid function tests) in the two groups, especially for the value of T3 in high-dose group were varied. However, 6 months after treatment, statistically significant differences between the two groups (P<0.05) were identified. In conclusion, 0.1 U/kg of GH is beneficial to children with GHD in attaining a satisfactory height, but it leads to insulin resistance. Thus, glucose metabolism and thyroid function should be monitored on a regular basis in a clinical setting.

Clonidine-stimulated growth hormone concentrations (cut-off values) measured by immunochemiluminescent assay (ICMA) in children and adolescents with short stature

OBJECTIVES

To establish cut-off values for growth hormone concentrations using clonidine as a secretagogue and an immunochemiluminescent assay as the method of measurement and to analyze the response time as well as the influence of gender, nutritional status and pubertal stage.

METHODS

A total of 225 tests were performed in 3 patient groups, categorized as group 1 (normal), group 2 (idiopathic short stature) and group 3 (growth hormone deficiency). Among the 199 disease-free individuals, 138 were prepubertal, and 61 were pubertal. Clonidine (0.1 mg/m2) was orally administered, and the growth hormone level was measured by immunochemiluminescent assay. The growth hormone peak and the difference between the growth hormone peak and the baseline level were then analyzed. Statistical analyses were performed using Student's t-test or the Mann-Whitney test and Kruskal-Wallis test followed by Dunn's post hoc test. Cut-off values were determined using a receiver operating characteristic curve.

RESULTS

Group 1 and group 2 had no difference in growth hormone peak, gender, body mass index standard deviation score, or pubertal stage. Group 3 exhibited a significantly lower growth hormone peak than the other groups did. The receiver operating characteristic curve demonstrated that growth hormone concentrations ≥ 3.0 ng/mL defined responsiveness to clonidine. In total, 3.02% of individuals in group 1 and group 2 were considered false positive, i.e., these children lacked growth hormone deficiency and had a peak below 3.0 ng/mL.

CONCLUSION

Clonidine-stimulated growth hormone concentrations ≥3 ng/mL, as measured by immunochemiluminescent assay, suggest responsiveness to the stimulus regardless of gender, body mass index standard deviation score or pubertal stage.

Neuroendocrine Regulation of Growth Hormone Secretion

This article reviews the main findings that emerged in the intervening years since the previous volume on hormonal control of growth in the section on the endocrine system of the Handbook of Physiology concerning the intra- and extrahypothalamic neuronal networks connecting growth hormone releasing hormone (GHRH) and somatostatin hypophysiotropic neurons and the integration between regulators of food intake/metabolism and GH release. Among these findings, the discovery of ghrelin still raises many unanswered questions. One important event was the application of deconvolution analysis to the pulsatile patterns of GH secretion in different mammalian species, including Man, according to gender, hormonal environment and ageing. Concerning this last phenomenon, a great body of evidence now supports the role of an attenuation of the GHRH/GH/Insulin-like growth factor-1 (IGF-1) axis in the control of mammalian aging.

Growth hormone deficiency after childhood bone marrow transplantation with total body irradiation: interaction with adiposity and age

OBJECTIVE

Bone marrow transplantation with total body irradiation (BMT/TBI) has adverse effects on growth, growth hormone status and adiposity. We investigated the GH-IGF-I axis in relation to adiposity.

DESIGN

Cross-sectional case control study.

PATIENTS

BMT/TBI survivors (n = 22) and short stature control participants (n = 19), all GH-naïve or off GH treatment >3 months.

MEASUREMENTS

Auxology, DEXA scans and GH-IGF-I axis investigation: (i) 12-h overnight GH profiles; (ii) insulin tolerance test (ITT); and (iii) IGF-I generation test.

ANALYSIS

auto-deconvolution of GH profile data and comparison of quantitative parameters using ANOVA.

RESULTS

Eighty-two percent of BMT/TBI survivors had growth hormone deficiency (GHD) using ITT. GH profile area-under-the-curve (GH-AUC) was reduced in BMT/TBI survivors vs short stature control participants [geometric mean (range) 209 (21-825) vs 428 (64-1400) mcg/l/12 h, respectively, P = 0·007]. GHD was more marked in those who had additional cranial irradiation (CRT) [ITT peak 1·4 (0·2-3·0) vs TBI only 4·1 (1·1-14·8) mcg/l, P = 0·036]. GHD was more marked at the end of growth in BMT/TBI survivors vs short stature control participants (GH-AUC 551 (64-2474) vs 1369 (192-4197) mcg/l/12 h, respectively, P = 0·011) and more prevalent (9/11 vs 1/9, respectively, P = 0·005). GH profile data were consistent with ITT results in 80% of participants. IGF-I generation tests were normal. BMT/TBI survivors still demonstrated lower GH levels after adjustment for adiposity (fat-adjusted mean difference for GH-AUC 90·9 mcg/l/12 h, P = 0·025).

CONCLUSIONS

GHD was more prevalent in BMT/TBI survivors than expected for the CRT dose in TBI, worsened with time and persisted into adulthood. GHD could not be explained by adiposity. There was no evidence of GH neurosecretory dysfunction or resistance after BMT/TBI.

Growth hormone responses to provocative tests in children with short stature

Growth hormone deficiency (GHD) is defined as a serum peak GH concentration <10 ng/mL with provocation as tested by a combination of at least two separate tests. The aim of this study was to compare two standard tests, insulin and levodopa (L-dopa), with a primary focus on specificity and accuracy. Clinical data were collected retrospectively from a review of 120 children who visited the pediatric endocrine clinic at Chonnam National University Hospital for the evaluation of short stature between January 2006 and April 2014. Subjects underwent GH provocation tests with insulin and L-dopa. Blood samples were obtained at 0, 15, 30, 45, 60, 90, and 120 min after administration, and GH levels were measured. In the insulin test, serial glucose levels were also checked, closely monitoring hypoglycemia. A total of 83 children (69.2%) were diagnosed with GHD and 37 children (30.8%) were diagnosed with idiopathic short stature (ISS). Peak GH levels were achieved an average of 45 min after the administration of insulin and L-dopa for both groups. The specificity and accuracy were 78.4% and 93.6% for the insulin test and 29.7% and 79.2% for L-dopa test, respectively. In the ISS group, the cumulative frequency of a GH cutoff value of >10 ng/mL at 120 min was 75.6% after insulin stimulation compared with 35.1% after L-dopa stimulation. Considering these results, we recommend performing the insulin test first to exclude ISS and then the L-dopa test for the diagnosis of GHD. This way, ISS patients are diagnosed after a single test, thus reducing hospital days and the burden of undergoing two serial tests.

Review of growth hormone therapy in adolescents and young adults with Prader-Willi syndrome

Consensus guidelines from the Growth Hormone Research Society Workshop recommend growth hormone therapy in all children with genetically confirmed Prader-Willi syndrome (PWS) in combination with dietary, lifestyle and environmental interventions. As yet, however, there are limited published data regarding the use of growth hormone therapy in adolescents and young adults with PWS. This review focuses on the advantages and disadvantages of growth hormone therapy in this particular group. The risk of complications, challenges with consent for therapy, the need for contraception in females with PWS and the appropriate monitoring required are all factors which must be carefully considered in this challenging patient group. Transition from paediatric to adult services can be difficult for most adolescents, but especially so for PWS adolescents and should be undertaken under the care of experienced paediatric and adult endocrinologists and a multidisciplinary team approach. Further research is, however, still required in the management of PWS patients during adolescence.

Hypothalamic distribution of somatostatin mRNA expressing neurones relative to pubertal and adult changes in pulsatile growth hormone secretion in mice

The age-associated decline in growth hormone (GH) secretion may be a consequence of the reduction in the number of GH-releasing hormone (GHRH) positive neurones. However, it remains unclear whether an alteration in the number or distribution of somatostatin (SST) neurones contributes to this change. In the present study, we characterised the role of SST in modulating the change in pulsatile GH secretion in male C57Bl/6J mice throughout puberty and into early adulthood. We assessed pulsatile GH secretion in mice at 4, 8 and 16 weeks of age. These ages correspond to early pubertal, early adulthood and adulthood, respectively. We show an elevation in peak, total and pulsatile GH secretion coinciding with periods of rapid linear growth. Using in situ hybridisation and morphometric methods, we mapped the distribution of Sst mRNA expression within the mouse brain relative to this change in pulsatile GH secretion. The results obtained show that altered pulsatile GH secretion in male mice from 4-16 weeks of age does not coincide with a significant change in the number of Sst mRNA expressing neurones or an abundance of Sst mRNA expression throughout the arcuate nucleus (ARC) and periventricular nucleus (PeV). Rather, we observed a progressive decline in Sst mRNA expressing neurones within subnuclei of the paraventricular nucleus at this time. We conclude that structural changes in Sst expression within the PeV and ARC may not reflect the observed decline in pulsatile GH secretion in mice from puberty into early adulthood.

Influence of body mass index on the growth hormone response to provocative testing in short children without growth hormone deficiency

Obesity and its related factors are known to suppress the secretion of growth hormone (GH). We aimed to evaluate the influence of body mass index (BMI) on the peak GH response to provocative testing in short children without GH deficiency. We conducted a retrospective review of medical records of 88 children (2-15 yr old) whose height was less than 3 percentile for one's age and sex, with normal results (peak GH level > 10 ng/mL) of GH provocative testing with clonidine and dopamine. Peak stimulated GH level, height, weight, pubertal status and serum IGF-1 level were measured. Univariate analysis showed that the BMI standard deviation score (SDS) correlated negatively with the natural log (ln) of the peak stimulated GH level (ln peak GH). BMI SDS did not correlate significantly with sex, age, pubertal status, or ln IGF-1 level. BMI SDS correlated negatively with ln peak GH level induced by clonidine but not by dopamine. In stepwise multivariate regression analysis, BMI SDS was the only significant predictor of ln peak GH level in the combination of tests and the clonidine test, but not in the dopamine test. In children without GH deficiency, BMI SDS correlates negatively with the peak GH level. BMI SDS should be included in the analysis of the results of GH provocation tests, especially tests with clonidine.

Height-based Indices of Pubertal Timing in Male Adolescents

It is important to account for timing of puberty when studying the adolescent brain and cognition. The use of classical methods for assessing pubertal status may not be feasible in some studies, especially in male adolescents. Using data from a sample of 478 males from a longitudinal birth cohort, we describe the calculations of three independent height-based markers of pubertal timing: Age at Peak Height Velocity (APHV), Height Difference in Standard Deviations (HDSDS), and Percent Achieved of Adult Stature (PAAS). These markers correlate well with each other. In a separate cross-sectional study, we show that the PAAS marker correlates well with testosterone levels and self-reported pubertal-stage scores. We conclude by discussing key considerations for investigators when drawing upon these methods of assessing pubertal timing.

Both estrogen receptor α and β stimulate pituitary GH gene expression

Although sex steroids have been implicated in the control of mammalian growth, their direct effect on GH synthesis is less clear. The aim of this study was to establish whether estradiol (E2) directly affects GH synthesis in somatotrophs. Somatotroph GH3 and MtT/S cells were used as in vitro models. At physiological doses of E2 stimulation, GH mRNA levels were increased and the ER antagonist ICI 182,780 completely abolished this effect. Estrogen receptor (ER) α- and ERβ-selective agonists, propylpyrazole triol (PPT), and 2,3-bis(4-hydroxyphenyl) propionitrile (DPN), respectively, augmented GH mRNA expression and secretion, whereas E2 and PPT, but not DPN increased prolactin (PRL) mRNA levels. E2, PPT, and DPN stimulated expression of the pituitary transcription factor Pou1f1 and increased its binding to the GH promoter. In vivo evidence of E2 effects on GH synthesis was obtained from the generation of the somatotroph-specific ERα knockout (sERα-KO) mouse model. Basal pituitary GH, PRL, POU1F1, and ERα mRNA expression levels were lower in sERα-KO mice compared with those in controls; whereas ERβ mRNA levels remained unchanged. E2 and DPN stimulated pituitary GH mRNA expression and serum GH levels in control and sERα-KO ovariectomized mice; however, serum GH levels were unchanged in PPT-treated ovariectomized sERα-KO mice. In these animal models, PRL mRNA levels increased after either E2 or PPT, but an increase was not seen after DPN treatment. Thus, we propose a mechanism by which estrogen directly regulates somatotroph GH synthesis at a pretranslational level. In contrast to the predominant effect of ERα in the lactotroph, these results support a role for both ERα and ERβ in the transcriptional control of Gh in the somatotroph and illustrate important differences in ER isoform specificity in the anterior pituitary gland.

Growth retardation in children with kidney disease

Growth failure is almost inextricably linked with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Growth failure in CKD has been associated with both increased morbidity and mortality. Growth failure in the setting of kidney disease is multifactorial and is related to poor nutritional status as well as comorbidities, such as anemia, bone and mineral disorders, and alterations in hormonal responses, as well as to aspects of treatment such as steroid exposure. This review covers updated management of growth failure in these children including adequate nutrition, treatment of metabolic alterations, and early administration of recombinant human growth hormone (GH).

Anterior pituitary cell networks

Both endocrine and non-endocrine cells of the pituitary gland are organized into structural and functional networks which are formed during embryonic development but which may be modified throughout life. Structural mapping of the various endocrine cell types has highlighted the existence of distinct network motifs and relationships with the vasculature which may relate to temporal differences in their output. Functional characterization of the network activity of growth hormone and prolactin cells has revealed a role for cell organization in gene regulation, the plasticity of pituitary hormone output and remarkably the ability to memorize altered demand. As such, the description of these endocrine cell networks alters the concept of the pituitary from a gland which simply responds to external regulation to that of an oscillator which may memorize information and constantly adapt its coordinated networks' responses to the flow of hypothalamic inputs.

Strategies for maximizing growth in puberty in children with short stature

The approach to the child with growth retardation who is in puberty remains an important clinical challenge. The use of high-dose growth hormone (GH), suppression of puberty with GnRH analogs in combination with GH, and the use of selective inhibitors of the aromatase enzyme with aromatase inhibitors (also in combination with GH) are all therapeutic choices that have been studied. Aromatase blockade effectively blocks estrogen production in males with a reciprocal increase in testosterone, and a new generation of aromatase inhibitors, including anastrozole, letrozole and exemestane, is under investigation in adolescent subjects with severe growth retardation. This class of drugs, if judiciously used for a window of time, offers promise as an adjunct treatment of growth delay in pubertal patients with GH deficiency, idiopathic short stature, testotoxicosis, and other disorders of growth. These evolving uses of aromatase inhibitors, however, represent off-label use of the product, and definitive data on their efficacy are not available for each of the conditions mentioned. Safety issues regarding bone health also require further study.

Growth hormone is positively associated with surrogate markers of bone turnover during puberty

BACKGROUND

Puberty is characterized by increases in growth hormone (GH) and insulin-like growth factor-1 (IGF-1) and the pubertal growth spurt. Bone formation and resorption also increase, consistent with increased bone metabolism.

OBJECTIVE

To determine the relationship between pubertal bone metabolism, GH and IGF-1. We hypothesized that bone turnover peaks at the time of greatest pubertal GH secretion.

DESIGN AND SUBJECTS

Subjects included 86 girls and boys, 9-17 years-old (BMI 10th-90th percentiles). Because higher endogenous GH secretion is associated with a higher nadir following oral glucose, we used the GH nadir following a 2-h OGTT as indicative of GH status. Fasting serum IGF-1, aminoterminal propeptide of type 1 procollagen (P1NP) and carboxy-terminal collagen crosslinks (CTX) were obtained. Subjects were grouped per expected timing of peak growth. Group 1: Tanner 1 girls and Tanner 1-2 boys (period preceding peak growth), Group 2: Tanner 2-3 girls and Tanner 3-4 boys (period of peak growth) and Group 3: Tanner 4-5 girls and Tanner 5 boys (period following peak growth).

RESULTS

GH peaked at mid-puberty (Group 2) and IGF-1 in late puberty (Group 3). P1NP and CTX were highest in mid-puberty compared with early and late puberty (P = 0·0009 and 0·006 in girls and P = 0·005 and 0·04 in boys). GH, but not IGF-1, correlated with P1NP (r = 0·46 in both genders, P ≤ 0·008) and CTX (r = 0·37 and 0·38, P = 0·04 and 0·02 in girls and boys, respectively). Similarly, on regression modelling, GH (but not IGF-1) predicted both bone turnover markers in both genders.

CONCLUSION

GH is strongly associated with pubertal bone metabolism, independent of systemic IGF-1 in girls and boys.

Mechanisms limiting body growth in mammals

Recent studies have begun to provide insight into a long-standing mystery in biology-why body growth in animals is rapid in early life but then progressively slows, thus imposing a limit on adult body size. This growth deceleration in mammals is caused by potent suppression of cell proliferation in multiple tissues and is driven primarily by local, rather than systemic, mechanisms. Recent evidence suggests that this progressive decline in proliferation results from a genetic program that occurs in multiple organs and involves the down-regulation of a large set of growth-promoting genes. This program does not appear to be driven simply by time, but rather depends on growth itself, suggesting that the limit on adult body size is imposed by a negative feedback loop. Different organs appear to use different types of information to precisely target their adult size. For example, skeletal and cardiac muscle growth are negatively regulated by myostatin, the concentration of which depends on muscle mass itself. Liver growth appears to be modulated by bile acid flux, a parameter that reflects organ function. In pancreas, organ size appears to be limited by the initial number of progenitor cells, suggesting a mechanism based on cell-cycle counting. Further elucidation of the fundamental mechanisms suppressing juvenile growth is likely to yield important insights into the pathophysiology of childhood growth disorders and of the unrestrained growth of cancer. In addition, improved understanding of these growth-suppressing mechanisms may someday allow their therapeutic suspension in adult tissues to facilitate tissue regeneration.