Testotoxicosis: Report of Two Cases, One with a Novel Mutation in LHCGR Gene

Familial male-limited precocious puberty due to an activating mutation of the LHCGR: a case report and literature review

Familial male-limited precocious puberty (FMPP) is a rare form of gonadotropin-independent precocious puberty that is caused by an activating mutation of the LHCGR gene. Herein, we report a case of FMPP with a mutation of the LHCGR gene in a Korean boy with familial history of precocious puberty through 3 generations. A 16-month-old boy presented with signs of precocious puberty, including pubic hair, acne, and increased growth velocity. The patient's grandfather and father had a history of precocious puberty and profound short stature. On physical examination, the patient had prepubertal testes with pubic hair development appropriate for Tanner stage II. The stretched penile length was 7 cm (>2 standard deviation score), and observed bone age was that of a 4-year-old boy. Laboratory findings showed high serum testosterone (5.74 ng/mL [appropriate for Tanner IV-V]; normal range, <0.05 ng/mL) with suppressed luteinizing hormone (<0.07 mIU/mL) and normal serum level of follicular stimulating hormone (0.56 mIU/mL; normal range, 0.38-1.11 mIU/mL). Genetic testing revealed a pathogenic variant of LHCGR (c.1730 C>T (p.Thr577Ileu)), confirming FMPP. Bicalutamide and anastrozole were administered, and pubertal progression was sufficiently suppressed without any specific side effects. To our knowledge, this is the first case of genetically confirmed FMPP in Korea.

Whole exome sequencing identifies a novel homozygous missense mutation of LHCGR gene in primary infertile women with empty follicle syndrome

AIM

The genetic basis of empty follicle syndrome (EFS) is largely unknown, and the aim of this study was to investigate the genetic causes of EFS in primary infertile women.

METHODS

Four affected women diagnosed with anovulation were recruited, and whole exome sequencing (WES) was requested for the genetic diagnosis of the cases. One hundred healthy controls were verified by Sanger sequencing.

RESULTS

A novel homozygous variant of the LHCGR gene (NM_000233:c.1847C>A) was revealed in one affected individual by WES. Trios analysis of the mutation revealed an autosomal recessive pattern. This LHCGR variant was absent in 100 healthy controls and predicted to be highly damaging to the function of LHCGR.

CONCLUSIONS

The novel variant extends the mutational spectrum of the LHCGR gene associated with female sterility, which promotes the prognostic value of testing for LHCGR mutations in infertile women with EFS.

Hormone- and antibody-mediated activation of the thyrotropin receptor

Thyroid stimulating hormone (TSH), through activation of its G protein-coupled thyrotropin receptor (TSHR), controls the synthesis of thyroid hormone (TH), an essential metabolic hormone^1-3. Aberrant signaling of TSHR by autoantibodies causes Graves' disease and hypothyroidism that affect millions of patients worldwide⁴. Here we report the active structures of TSHR with TSH and an activating autoantibody M22⁵, both bound to an allosteric agonist ML-109⁶, as well as an inactivated TSHR structure with inhibitory antibody K1-70⁷. Both TSH and M22 push the extracellular domain (ECD) of TSHR into the upright active conformation. In contrast, K1-70 blocks TSH binding and is incapable of pushing the ECD to the upright conformation. Comparisons of the active and inactivated structures of TSHR with those of the luteinizing hormone-choriogonadotropin receptor (LHCGR) reveal a universal activation mechanism of glycoprotein hormone receptors, in which a conserved 10-residue fragment (P10) from the hinge C-terminal loop mediates ECD interactions with the TSHR transmembrane domain⁸. One surprisingly feature is that there are over 15 cholesterols surrounding TSHR, supporting its preferential location in lipid rafts⁹. These structures also highlight a similar ECD-push mechanism for TSH and autoantibody M22 to activate TSHR, thus providing the molecular basis for Graves' disease.

Long-Term Treatment With Letrozole in a Boy With Familial Male-Limited Precocious Puberty

BACKGROUND

The long-term follow-up in children with familial male-limited precocious puberty (FMPP) who were treated with letrozole, triptorelin, and spironolactone is limited, especially considering the efficiency and safety.

OBJECTIVE

We describe the clinical characteristics and long-term treatment with letrozole on adult height of a boy diagnosed with FMPP, confirmed by analysis of the LHCGR gene.

METHODS

Physical examinations, bone age (BA), testosterone, and gonadotropin levels were measured as well as gene sequencing of the proband and parents.

RESULTS

The boy was referred to the hospital at 3.1 years of age due to peripheral precocious puberty. His height was 116.8cm (+5.1SD) and BA was 9 years. Genetic analysis revealed a patrilineal c.1703C>T.(p.Ala568Val) mutation of the LHCGR gene. After treating with letrozole for 1.6 years, the height according to BA went from -3.52SD to -2.82SD. Triptorelin was added at age 4.7 years based on both the evidence of central puberty and his growth velocity according to BA. During the 6.9 years of treatment, he had a height gain of 51.9cm, and BA increased 5.2 years. At age 10, his present height is 168.7cm (0.05SD) and BA is 14.7 years. No adverse effects of treatment were encountered.

CONCLUSION

A patrilineal mutation of the LHCGR gene has been identified in a boy with FMPP. His height is 168.7cm (-0.05SD) which is approaching his adult height after long-term treatment with letrozole, triptorelin, and spironolactone.

Peripheral precocious puberty in a girl with an intracranial hCG-producing tumor: case report and literature review

Human chorionic gonadotropin (hCG)-producing tumors cause peripheral precocious puberty (PP) in boys, but generally not in girls. Homology between LH and hCG activates the LH receptor in testicular Leydig cells, increases testosterone production, and causes virilization. However, since FSH action is required for follicle development, hCG action alone does not increase estradiol (E2) production and does not cause feminization. Only a few cases of peripheral PP with hCG tumors in girls have been reported. We describe the case of a 7-year-old Japanese girl with peripheral PP associated with an hCG-producing tumor. She had prolonged vomiting, loss of appetite, and Tanner stage III breast development. Although no apparent increase in growth rate, bone age was advanced at 9.8 years. Serum E2 was slightly elevated and LH and FSH were below the measurement sensitivity, and abdominal ultrasonography and computed tomography images showed no abnormal findings in the uterus or ovaries. Subsequently, she developed visual field disturbance and loss of consciousness, and brain magnetic resonance imaging revealed an intracranial tumor. Based on pathological findings and abnormally high serum hCG-β level (48,800 IU/L), intracranial choriocarcinoma was diagnosed. 2.5 months after the start of chemotherapy, the hCG-β level became almost negative and the breast development disappeared synchronously. Tissue immunostaining of the tumor showed strong positivity for aromatase and hCG, indicating that the choriocarcinoma cells themselves may have produced estrogen via aromatase. This unique case highlights the possibility that hCG-producing tumors can cause peripheral PP in girls as well as boys.

A Case of Familial Male-limited Precocious Puberty with a Novel Mutation

Familial male-limited precocious puberty (FMPP), also known as testotoxicosis, is a rare cause of precocious puberty in males. It is caused by a mutation in the luteinizing hormone/chorionic gonadotropin receptor (LHCGR) gene, resulting in the receptor being constitutively activated. This causes excessive production of testosterone, leading to precocious puberty in males. Generally, boys present with signs of puberty, such as pubic hair growth, acne, and increased height velocity around the age of 2-4 years old. Like any other cause of precocious puberty, the goal of treatment is to prevent virilization and also delay closure of the epiphyseal plates to maintain adult height potential. Treatment, therefore, is aimed at decreasing the effects of testosterone, as well as stopping the conversion of testosterone to estrogen. Little is known about the long-term effects of treatment because the disorder is so rare. However, studies using bicalutamide and anastrozole have been promising. In this report, we present a boy with FMPP with a novel mutation in the LHCGR gene, who has been responding well to therapy using both drugs.

Testotoxicosis without Testicular Mass: Revealed by Peripheral Precocious Puberty and Confirmed by Somatic LHCGR Gene Mutation

Purpose: Testotoxicosis is an autosomal dominant form of limited gonadotropin-independent precocious puberty in boys. It is caused by a heterozygous constitutively activating mutation of the LHCGR gene encoding the luteinizing/hormone receptor (LHR). Some twenty mutations of the LHCGR gene have been reported. Most of them are constitutive mutations isolated from blood leukocyte DNA, although others are somatic, found only in testicular tumoural tissue. In all the previously reported cases of these somatic mutations, the tumour, whether a nodular Leydig cell adenoma or hyperplasia, was easily visible on testicular ultrasonography. The aim of this study was to describe an unusual presentation of a patient with the clinical and hormonal characteristics of testotoxicosis but no well-circumscribed lesion at testicular ultrasonography.Materials and Methods: Molecular analysis of the LHCGR gene was performed by direct sequencing of DNA extracted from peripheral leucocytes and testicular biopsy.Results: Molecular analysis didn't find any LHR mutation in blood, whereas it revealed for the first time a somatic D578H mutation in testicular tissue despite no evidence of a nodular aspect at testis ultrasonography.Conclusions: This observation underlines the need to look for a somatic LHCGR gene mutation from the testicular biopsies of all boys with testotoxicosis with no constitutive LHCGR gene mutation identified from blood DNA, even in the absence of circumscribed testicular lesion at ultrasonography. In addition, based on the known link between LHR mutations and testicular tumourigenesis, yearly ultrasound monitoring of the testes should be considered for these patients.

Leucine Rich Repeat Proteins: Sequences, Mutations, Structures and Diseases

Mutations in the genes encoding Leucine Rich Repeat (LRR) containing proteins are associated with over sixty human diseases; these include high myopia, mitochondrial encephalomyopathy, and Crohn's disease. These mutations occur frequently within the LRR domains and within the regions that shield the hydrophobic core of the LRR domain. The amino acid sequences of fifty-five LRR proteins have been published. They include Nod-Like Receptors (NLRs) such as NLRP1, NLRP3, NLRP14, and Nod-2, Small Leucine Rich Repeat Proteoglycans (SLRPs) such as keratocan, lumican, fibromodulin, PRELP, biglycan, and nyctalopin, and F-box/LRR-repeat proteins such as FBXL2, FBXL4, and FBXL12. For example, 363 missense mutations have been identified. Replacement of arginine, proline, or cysteine by another amino acid, or the reverse, is frequently observed. The diverse effects of the mutations are discussed based on the known structures of LRR proteins. These mutations influence protein folding, aggregation, oligomerization, stability, protein-ligand interactions, disulfide bond formation, and glycosylation. Most of the mutations cause loss of function and a few, gain of function.

Diseases caused by mutations in luteinizing hormone/chorionic gonadotropin receptor

Accumulating evidence showed that the luteinizing hormone/chorionic gonadotropin receptor (LHCGR) is an essential regulator of sexual development and reproduction from zebrafish to human. Activating and inactivating mutations of LHCGR gene have been identified from patients of different phenotypes. Familial male-limited precocious puberty, Leydig cell hypoplasia, and empty follicle syndrome are caused by LHCGR mutations. More than 50 mutations have been reported from subjects of different ethnic backgrounds. Functional analyses of the mutant LHCGR revealed multiple defects, including cell surface expression, ligand binding, and signaling. The difference of the two native ligands and signaling pathway activated by LHCGR are illustrated. Potential therapeutic implications from the analyses of the naturally occurring LHCGR mutations, such as pharmacological chaperones, are highlighted.

A Case of Familial Male-Limited Precocious Puberty in a Child With Klinefelter Syndrome

Familial male-limited precocious puberty (FMPP) is an autosomal dominant, male-limited disorder that causes peripheral precocious puberty in boys. Klinefelter syndrome (47, XXY) is the most common chromosomal aberration in males with associated infertility, hypogonadism, and learning disability. We report here a case of Klinefelter syndrome in a patient with FMPP. A 6-year-old boy was referred to our pediatric endocrinology department for accelerated linear growth and premature pubic hair development. He was diagnosed with FMPP based on clinical, laboratory, and genetic sequencing. Increased levels of gonadotropins prompted further investigation, leading to a subsequent diagnosis of Klinefelter syndrome through karyotype analysis. This case illustrates that patients with FMPP and elevated gonadotropins should encourage further investigation by physicians. We recommend the use of karyotype analysis in such patients who are not receiving aromatase inhibitor therapy. We hypothesize that his mutation or pretreatment with aromatase inhibitors may have a protective effect on testosterone production and sperm viability.

Central precocious puberty in a case of late-diagnosed familial testotoxicosis and long-term treatment monitoring

Familial testotoxicosis is a disease with autosomal dominant inheritance that only affects men and which causes gonadotropin-independent precocious puberty. Although basal levels of luteinizing hormone and follicle-stimulating hormone are low, similar to what is expected in the pre-pubertal period, testosterone levels are high. Bicalutamide as an anti-androgen medication and anastrozole as an aromatase inhibitor have been proposed as agents that can be safely used in children. In the present study, we present the case of coexistent familial testotoxicosis and central precocious puberty induced by long-term androgen exposure in a patient aged 7.5 years, whose clinical symptoms started at the age of 4 years. Along with our experience with the effects of long-term (3 years) anastrozole plus bicalutamide treatment in this case, we discuss the relevant literature.

Adult height in patients with familial male-limited precocious puberty and the role of an aromatase inhibitor in patient management

BACKGROUND

There is little adult height data in patients with familial male-limited precocious puberty (FMPP) and no management consensus. We assessed the treatment and adult height in local patients with FMPP and those reported in the literature.

METHODS

Growth data were obtained on four local patients with FMPP and a search performed to obtain management details and adult height data on cases in the literature. UK (90) population standards were used to calculate standard deviation scores (SDS).

RESULTS

Adult height data were available on 25 men with FMPP of whom 21 were treated. Median adult height SDS of patients was -1.5 SD with a mid-parental target of -0.6 SD (p=0.1). Eight patients (32%) had an adult height above the mid-parental target and seven patients (28%) had a height >2 SD below the mean. The median height SD was -0.03 in untreated patients and +0.5 SD in those receiving an aromatase inhibitor. There was no relationship between height and age at presentation.

CONCLUSIONS

Aromatase inhibitor therapy is associated with a positive height outcome in FMPP but the outcome with and without intervention is unpredictable. Clinicians need to be cautious when counselling families about the potential height outcome in FMPP.

Familial Hypocalciuric Hypercalcemia as an Atypical Form of Primary Hyperparathyroidism

Familial hypocalciuric hypercalcemia (FHH) causes lifelong hypercalcemia with features that overlap with typical primary hyperparathyroidism (PHPT). The incompleteness of this overlap has led to divergent nomenclatures for FHH. I compare two nomenclatures. One sets FHH as an entity distinct from PHPT. The other groups FHH with PHPT but conditions FHH as atypical PHPT. I analyzed selected articles about calcium-sensing receptors, FHH, PHPT, CASR, GNA11, and AP2S1. FHH usually results from a heterozygous germline inactivating mutation of the CASR, and less frequently from mutation of GNA11 or AP2S1. The CASR encodes the calcium-sensing receptors. These are highly expressed on parathyroid cells, where they sense serum calcium concentration and regulate suppression of PTH secretion by serum calcium. Their mutated expression in the kidney in FHH causes increased renal tubular reabsorption of calcium (hypocalciuria). Many FHH features are shared with PHPT and thus support FHH as a form of PHPT. These include a driver mutation expressed mainly in the parathyroid cells. The mutation causes a parathyroid cell insensitivity to extracellular calcium in vivo and in vitro, a right-shift of the set point for suppression of PTH secretion by calcium. Serum PTH is normal or mildly elevated; ie, it is not appropriately suppressed by hypercalcemia. Total parathyroidectomy causes hypoparathyroidism and durable remission of hypercalcemia. Some other features are not shared with PHPT and could support FHH as a distinct entity. These include onset of hypercalcemia in the first week of life, frequent persistence of hypercalcemia after subtotal parathyroidectomy, and hypocalciuria. The features supporting FHH as a form of PHPT are stronger than those favoring FHH as a distinct entity. Classifying FHH as an atypical form of PHPT represents compact nomenclature and supports current concepts of pathophysiology of FHH and PHPT. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.