Hypogonadism in a patient with a mutation in the luteinizing hormone beta-subunit gene

Luteinizing hormone β-subunit deficiency: Report of a novel LHB likely pathogenic variant and a systematic review of the published literature

CONTEXT

Selective deficiency of β-subunit of luteinizing hormone (LHB) is a rare disease with scarce data on its characteristics.

OBJECTIVES

To describe a male with LHB deficiency and systematically review the literature.

DESIGN AND PATIENTS

Description of a male patient with LHB deficiency and a systematic review of LHB deficiency patients published to date (10 males and 3 females) as per PRISMA guidelines.

RESULTS

A 36-year-old Asian Indian male presented with infertility. On evaluation, he had sexual maturity of Tanner's stage 3, low testosterone (0.23 ng/ml), low LH (0.44 mIU/ml), high follicle-stimulating hormone (FSH, 22.4 mIU/ml), and a novel homozygous missense likely pathogenic variant (p.Cys46Arg) in LHB. In the molecular dynamics simulation study, this variant interferes with heterodimerization of alpha-beta subunits. Eleven males with pathogenic variants in LHB reported to date, presented at a median age of 29 (17-38) years, most commonly with delayed puberty. Clinical and biochemical profiles were similar to those of our patient. In the majority, testosterone monotherapy modestly increased testicular volume whereas human chorionic gonadotropin (hCG) monotherapy also improved spermatogenesis. In females, oligomenorrhoea after spontaneous menarche was the most common manifestation. Ten pathogenic/likely pathogenic variants (three in-frame deletions, three missense, two splice-site, one nonsense, and one frameshift variants) have been reported in nine index patients.

CONCLUSION

We report a novel likely pathogenic LHB variant in an Asian Indian patient. The typical phenotype in male patients with LHB deficiency is delayed puberty with low testosterone, low LH, and normal to high FSH and hCG monotherapy being the best therapeutic option.

Emerging concepts on Leydig cell development in fetal and adult testis

Leydig cells (Lc) reside in the interstitial compartment of the testis and are the target of Luteinising hormone (LH) for Testosterone (T) production, thus critically regulates male fertility. Classical histological studies have identified two morphologically different populations of Lc during testicular development [fetal (FLc) and adult (ALc)]. Recent progress in ex vivo cell/organ culture, genome-wide analysis, genetically manipulated mouse models, lineage tracing, and single-cell RNA-seq experiments have revealed the diverse cellular origins with differential transcriptomic and distinct steroidogenic outputs of these populations. FLc originates from both coelomic epithelium and notch-active Nestin-positive perivascular cells located at the gonad-mesonephros borders, and get specified as Nr5a1 (previously known as Ad4BP/SF-1) expressing cells by embryonic age (E) 12.5 days in fetal mouse testes. These cells produce androstenedione (precursor of T, due to lack of HSD17β3 enzyme) and play critical a role in initial virilization and patterning of the male external genitalia. However, in neonatal testis, FLc undergoes massive regression/dedifferentiation and gradually gets replaced by T-producing ALc. Very recent studies suggest a small fraction (5-20%) of FLc still persists in adult testis. Both Nestin-positive perivascular cells and FLc are considered to be the progenitor populations for ALc. This minireview article summarizes the current understanding of Lc development in fetal and adult testes highlighting their common or diverse cellular (progenitor/stem) origins with respective functional significance in both rodents and primates. (227 words).

Revisiting the gonadotropic regulation of mammalian spermatogenesis: evolving lessons during the past decade

Spermatogenesis is a multi-step process of male germ cell (Gc) division and differentiation which occurs in the seminiferous tubules of the testes under the regulation of gonadotropins - Follicle Stimulating Hormone (FSH) and Luteinising hormone (LH). It is a highly coordinated event regulated by the surrounding somatic testicular cells such as the Sertoli cells (Sc), Leydig cells (Lc), and Peritubular myoid cells (PTc). FSH targets Sc and supports the expansion and differentiation of pre-meiotic Gc, whereas, LH operates via Lc to produce Testosterone (T), the testicular androgen. T acts on all somatic cells e.g.- Lc, PTc and Sc, and promotes the blood-testis barrier (BTB) formation, completion of Gc meiosis, and spermiation. Studies with hypophysectomised or chemically ablated animal models and hypogonadal (hpg) mice supplemented with gonadotropins to genetically manipulated mouse models have revealed the selective and synergistic role(s) of hormones in regulating male fertility. We here have briefly summarized the present concept of hormonal control of spermatogenesis in rodents and primates. We also have highlighted some of the key critical questions yet to be answered in the field of male reproductive health which might have potential implications for infertility and contraceptive research in the future.

Reversible hypogonadotropic hypogonadism in men with the fertile eunuch/Pasqualini syndrome: A single-center natural history study

Congenital hypogonadotropic hypogonadism (HH) is a heterogeneous genetic disorder characterized by disrupted puberty and infertility. In most cases, HH is abiding yet 10-15% undergo reversal. Men with HH and absent and partial puberty (i.e., testicular volume <4mL and >4mL respectively) have been well-studied, but the rare fertile eunuch (FE) variant remains poorly characterized. This natural history study of 240 men with HH delineates the clinical presentation, neuroendocrine profile, rate of reversal and genetics of the FE variant. We compared three HH groups: FE (n=38), absent puberty (n=139), and partial puberty (n=63). The FE group had no history of micropenis and 2/38 (5%) had cryptorchidism (p<0.0001 vs. other groups). The FE group exhibited higher rates of detectable gonadotropins, higher mean LH/FSH levels, and higher serum inhibin B levels (all p<0.0001). Neuroendocrine profiling showed pulsatile LH secretion in 30/38 (79%) of FE men (p<0.0001) and 16/36 (44%) FE men underwent spontaneous reversal of HH (p<0.001). The FE group was enriched for protein-truncating variants (PTVs) in GNRHR and FGFR1 and 4/30 (13%) exhibited oligogenic PTVs. Findings suggest men with the FE variant exhibit the mildest neuroendocrine defects of HH men and the FE sub-type represents the first identified phenotypic predictor for reversible HH.

Genetic variants of gonadotrophins and their receptors: Impact on the diagnosis and management of the infertile patient

This narrative review is concerned with genetic variants of the genes encoding gonadotrophin subunits and their receptors, as well as their implications into the diagnosis and treatment of infertility. We first review briefly the basics of molecular biology and biochemistry of gonadotrophin and gonadotrophin receptor structure and function, then describe the phenotypic effects of polymorphisms and mutations of these genes, followed by diagnostic aspects. We will then summarise the information that inactivating gonadotrophin receptor mutations have provided about the controversial topic of extragonadal gonadotrophin action. Finally, we will close with the current and future therapeutic approaches on patients with gonadotrophin and their receptor mutations.

Genetics of congenital central hypogonadism

The diagnostic suspicion of congenital central hypogonadism is based on clinical signs. Biochemical confirmation is challenging, especially after the postnatal activation stage of the hypothalamic-pituitary-testicular axis. Sertoli cell markers, like AMH and inhibin B, have become useful tools for the diagnosis of male central hypogonadism during childhood. Different mechanisms can participate in the aetiopathogenesis of central hypogonadism, leading to a deficiency in the production of gonadotrophins. Advances in genetic studies, mainly next generation sequencing techniques, have allowed the discovery of a large number of genes related to central hypogonadism. However, a causal variant is found in approximately half of the patients. Central hypogonadism has been classically described as a pathology with variable expressivity and incomplete penetrance. Currently, these characteristics are known to be partially explained by the presence of oligogenicity, that is the participation of variants in more than one gene in the aetiology of central hypogonadism in the same patient.

The Roles of Luteinizing Hormone, Follicle-Stimulating Hormone and Testosterone in Spermatogenesis and Folliculogenesis Revisited

Spermatogenesis and folliculogenesis involve cell–cell interactions and gene expression orchestrated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). FSH regulates the proliferation and maturation of germ cells independently and in combination with LH. In humans, the requirement for high intratesticular testosterone (T) concentration in spermatogenesis remains both a dogma and an enigma, as it greatly exceeds the requirement for androgen receptor (AR) activation. Several data have challenged this dogma. Here we report our findings on a man with mutant LH beta subunit (LHβ) that markedly reduced T production to 1–2% of normal., but despite this minimal LH stimulation, T production by scarce mature Leydig cells was sufficient to initiate and maintain complete spermatogenesis. Also, in the LH receptor (LHR) knockout (LuRKO) mice, low-dose T supplementation was able to maintain spermatogenesis. In addition, in antiandrogen-treated LuRKO mice, devoid of T action, the transgenic expression of a constitutively activating follicle stimulating hormone receptor (FSHR) mutant was able to rescue spermatogenesis and fertility. Based on rodent models, it is believed that gonadotropin-dependent follicular growth begins at the antral stage, but models of FSHR inactivation in women contradict this claim. The complete loss of FSHR function results in the complete early blockage of folliculogenesis at the primary stage, with a high density of follicles of the prepubertal type. These results should prompt the reassessment of the role of gonadotropins in spermatogenesis, folliculogenesis and therapeutic applications in human hypogonadism and infertility.

Successful pregnancy after ovulation induction with human chorionic gonadotropin in a woman with selective luteinising hormone deficiency

Selective LH deficiency has been described in several men, but only in two women who presented normal pubertal development but secondary amenorrhoea due to anovulation. Despite its rarity, this condition represents a valuable model for studying the processes regulated by FSH or LH during late folliculogenesis and ovulation in humans. A woman previously diagnosed with selective LH deficiency due to a homozygous germline splice site mutation in LHB (IVS2 + 1G→C mutation) was submitted to an individualised ovarian induction protocol, first with recombinant LH and then with highly purified urinary hCG. Ovarian follicle growth and ovulation were achieved, and a healthy baby was born after an uneventful term pregnancy. The treatment described herein demonstrates that the clinical actions of exogenous LH or hCG in inducing late-stage follicular development in women with deficient LH production or performance might be interchangeable or inevitable, once FSH-dependent early follicular growth is assured.

Genetics of hypogonadotropic Hypogonadism-Human and mouse genes, inheritance, oligogenicity, and genetic counseling

Hypogonadotropic hypogonadism, which may be normosmic (nHH) or anosmic/hyposmic, known as Kallmann syndrome (KS), is due to gonadotropin-releasing hormone deficiency, which results in absent puberty and infertility. Investigation of the genetic basis of nHH/KS over the past 35 years has yielded a substantial increase in our understanding, as variants in 44 genes in OMIM account for ~50% of cases. The first genes for KS (ANOS1) and nHH (GNRHR) were followed by the discovery that FGFR1 variants may cause either nHH or KS. Associated anomalies include midline facial defects, neurologic deficits, cardiac anomalies, and renal agenesis, among others. Mouse models for all but one gene (ANOS1) generally support findings in humans. About half of the known genes implicated in nHH/KS are inherited as autosomal dominant and half are autosomal recessive, whereas only 7% are X-linked recessive. Digenic and oligogenic inheritance has been reported in 2-20% of patients, most commonly with variants in genes that may result in either nHH or KS inherited in an autosomal dominant fashion. In vitro analyses have only been conducted for both gene variants in eight cases and for one gene variant in 20 cases. Rigorous confirmation that two gene variants in the same individual cause the nHH/KS phenotype is lacking for most. Clinical diagnosis is probably best accomplished by targeted next generation sequencing of the known candidate genes with confirmation by Sanger sequencing. Elucidation of the genetic basis of nHH/KS has resulted in an enhanced understanding of this disorder, as well as normal puberty, which makes genetic diagnosis clinically relevant.

[Molecular genetics and phenotypic features of congenital isolated hypogonadotropic hypogonadism]

Congenital isolated hypogonadotropic hypogonadism includes a group of diseases related to the defects of secretion and action of gonadotropin-releasing hormone (GNRH) and gonadotropins. In a half of cases congenital hypogonadism is associated with an impaired sense of smell. It's named Kallmann syndrome. Now 40 genes are known to be associated with function of hypothalamus pituitary gland and gonads. Phenotypic features of hypogonadism and therapy effectiveness are related to different molecular defects. However clinical signs may vary even within the same family with the same molecular genetic defect. Genotype phenotype correlation in patients with congenital malformations prioritizes the search for mutations in candidate genes. There are data of significant contribution of oligogenicity into the phenotype of the disease are presented in the review. Moreover, an issue of current isolated hypogonadotropic hypogonadism definition and classification revision is raised in the review due to hypogonadotropic hypogonadism development while there are mutations in genes not associated with GNRH neurons secretion and function.

Androgen Treatment in Adolescent Males With Hypogonadism

During adolescence, androgens are responsible for the development of secondary sexual characteristics, pubertal growth, and the anabolic effects on bone and muscle mass. Testosterone is the most abundant testicular androgen, but some effects are mediated by its conversion to the more potent androgen dihydrotestosterone (DHT) or to estradiol. Androgen deficiency, requiring replacement therapy, may occur due to a primary testicular failure or secondary to a hypothalamic–pituitary disorder. A very frequent condition characterized by a late activation of the gonadal axis that may also need androgen treatment is constitutional delay of puberty. Of the several testosterone or DHT formulations commercially available, very few are employed, and none is marketed for its use in adolescents. The most frequently used androgen therapy is based on the intramuscular administration of testosterone enanthate or cypionate every 3 to 4 weeks, with initially low doses. These are progressively increased during several months or years, in order to mimic the physiology of puberty, until adult doses are attained. Scarce experience exists with oral or transdermal formulations. Preparations containing DHT, which are not widely available, are preferred in specific conditions. Oxandrolone, a non-aromatizable drug with higher anabolic than androgenic effects, has been used in adolescents with preserved testosterone production, like Klinefelter syndrome, with positive effects on cardiometabolic health and visual, motor, and psychosocial functions. The usual protocols applied for androgen therapy in boys and adolescents are discussed.

Morphometric Evaluation of Spermatogenic Cells and Seminiferous Tubules and Exploration of Luteinizing Hormone Beta Polypeptide in Testis of Datong Yak

Simple Summary

Previous studies revealed that luteinizing hormone βeta polypeptide (LHB) plays an essential role in fertilization. Therefore, we aimed to confirm the importance of LHB in the testis of yak and to determine their association with male yak fertility. Histomorphological analysis of the testes is essential for predicting the fertilizing ability of the bull. To the best our knowledge, this is the first study to evaluate the micro anatomical changes and histometric alternation in testes of Datong yak. These findings could help to predict the sperm production capacity and to understand the specific molecular mechanisms of LHB during spermatogenesis.

Abstract

Histological examination of testes is essential for understanding infertility, sex development, and growth. Therefore, to understand the histomorphology of testes at different developmental stages, we performed hematoxylin and eosin staining of Yak testis. Our results revealed that the diameters of spermatogenic cells and their nuclei were significantly larger (p < 0.05) in the testis at six years compared to at six and 18 months. No significant difference was noted between 30 months and six years. The study was designed to compare the expression profile of LHB in Datong yak. The expression pattern of LHB was explored using quantitative PCR, semi-quantitative PCR, molecular bioinformatic, and Western blot analysis. Our observations indicated that expression of LHB was significantly higher (p < 0.05) in the testis of Datong yak. Western blotting indicated that the molecular mass of LHB protein was 16 kDa in yak. The protein encoded by yak LHB included conserved cysteine-knot domain regions. The high expression of LHB in testis indicated that LHB may be vital for the development of male gonads and the fertility of Datong yak.

Gonadotropins and their receptors: coevolution, genetic variants, receptor imaging, and functional antagonists

Gonadotropins belong to the family of dimeric glycoprotein hormones and regulate gonadal physiology mediated by G protein-coupled, seven-transmembrane receptors. These glycoprotein hormones are widely used in the clinic to promote ovarian follicle development and for treating some cases of male infertility. We traced the coevolution of dimeric gonadotropin hormones and their receptors, together with thyrotropin and its receptor. We updated recent findings on human genetic variants of these genes and their association with dizygotic twining, polycystic ovarian syndrome, primary ovarian insufficiency, male-limited precocious puberty, and infertility. In addition to the known physiological roles of gonadotropin-receptor signaling in gonadal tissues, we also discussed emerging understanding of extragonadal functions of gonadotropins in bones and adipose tissues, together with recent advances in in vivo imaging of gonadotropin receptors in live animals. Recent development of gonadotropin receptor agonists and antagonists were summarized with an emphasis on the development of functional antagonists for FSH receptors to alleviate osteoporosis and obesity associated with menopause.

Two Hormones for One Receptor: Evolution, Biochemistry, Actions, and Pathophysiology of LH and hCG

LH and chorionic gonadotropin (CG) are glycoproteins fundamental to sexual development and reproduction. Because they act on the same receptor (LHCGR), the general consensus has been that LH and human CG (hCG) are equivalent. However, separate evolution of LHβ and hCGβ subunits occurred in primates, resulting in two molecules sharing ~85% identity and regulating different physiological events. Pituitary, pulsatile LH production results in an ~90-minute half-life molecule targeting the gonads to regulate gametogenesis and androgen synthesis. Trophoblast hCG, the "pregnancy hormone," exists in several isoforms and glycosylation variants with long half-lives (hours) and angiogenic potential and acts on luteinized ovarian cells as progestational. The different molecular features of LH and hCG lead to hormone-specific LHCGR binding and intracellular signaling cascades. In ovarian cells, LH action is preferentially exerted through kinases, phosphorylated extracellular-regulated kinase 1/2 (pERK1/2) and phosphorylated AKT (also known as protein kinase B), resulting in irreplaceable proliferative/antiapoptotic signals and partial agonism on progesterone production in vitro. In contrast, hCG displays notable cAMP/protein kinase A (PKA)-mediated steroidogenic and proapoptotic potential, which is masked by estrogen action in vivo. In vitro data have been confirmed by a large data set from assisted reproduction, because the steroidogenic potential of hCG positively affects the number of retrieved oocytes, and LH affects the pregnancy rate (per oocyte number). Leydig cell in vitro exposure to hCG results in qualitatively similar cAMP/PKA and pERK1/2 activation compared with LH and testosterone. The supposed equivalence of LH and hCG has been disproved by such data, highlighting their sex-specific functions and thus deeming it an oversight caused by incomplete understanding of clinical data.

The gonadotropin system, lessons from animal models and clinical cases

This review article centers upon family of gonadotropin hormones which consists of two pituitary hormones - follicle-stimulating hormone (FSH) and luteinizing hormone (LH) as well as one non-pituitary hormone - human chorionic gonadotropin (hCG) secreted by placenta, and their receptors. Gonadotropins play an essential role in proper sexual development, puberty, gametogenesis, maintenance of pregnancy and male sexual differentiation during the fetal development. They belong to the family of glycoprotein hormones thus they constitute heterodimeric proteins built of common α subunit and hormone-specific β-subunit. Hitherto, several mutations in genes encoding both gonadotropins and their receptors have been identified in humans. Their occurrence resulted in a number of different phenotypes including delayed puberty, primary amenorrhea, hermaphroditism, infertility and hypogonadism. In order to understand the effects of mutations on the phenotype observed in affected patients, detailed molecular studies are required to map the relationship between the structure and function of gonadotropins and their receptors. Nonetheless, in vitro assays are often insufficient to understand physiology. Therefore, several animal models have been developed to unravel the physiological roles of gonadotropins and their receptors.

GENETICS IN ENDOCRINOLOGY: Genetic counseling for congenital hypogonadotropic hypogonadism and Kallmann syndrome: new challenges in the era of oligogenism and next-generation sequencing

Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) are rare, related diseases that prevent normal pubertal development and cause infertility in affected men and women. However, the infertility carries a good prognosis as increasing numbers of patients with CHH/KS are now able to have children through medically assisted procreation. These are genetic diseases that can be transmitted to patients' offspring. Importantly, patients and their families should be informed of this risk and given genetic counseling. CHH and KS are phenotypically and genetically heterogeneous diseases in which the risk of transmission largely depends on the gene(s) responsible(s). Inheritance may be classically Mendelian yet more complex; oligogenic modes of transmission have also been described. The prevalence of oligogenicity has risen dramatically since the advent of massively parallel next-generation sequencing (NGS) in which tens, hundreds or thousands of genes are sequenced at the same time. NGS is medically and economically more efficient and more rapid than traditional Sanger sequencing and is increasingly being used in medical practice. Thus, it seems plausible that oligogenic forms of CHH/KS will be increasingly identified making genetic counseling even more complex. In this context, the main challenge will be to differentiate true oligogenism from situations when several rare variants that do not have a clear phenotypic effect are identified by chance. This review aims to summarize the genetics of CHH/KS and to discuss the challenges of oligogenic transmission and also its role in incomplete penetrance and variable expressivity in a perspective of genetic counseling.

Homozygous nonsense mutation Trp28X in the LHB gene causes male hypogonadism

PURPOSE

The purpose of this study was to investigate a novel mutation in the luteinizing hormone beta-subunit (LHB) gene in one male patient with hypogonadism due to selective luteinizing hormone (LH) deficiency.

METHODS

Sanger sequencing of one 28-year-old man born to consanguineous parents was performed. Treatment with human chorionic gonadotropin (hCG) (2000 IU, twice a week) was initiated for 3 months, followed by 5000 IU weekly to date.

RESULTS

We identified a novel c.84G>A[p.W28X] nonsense LHB mutation. The W28X mutation produces a truncated LHB peptide of seven amino acids, which prevents the synthesis of intact LH. After 40 days of treatment with hCG, the patient exhibited a few spermatozoa in the semen. Treated for 6 months, the patient exhibited normal seminal parameters.

CONCLUSIONS

We identified a novel mutation in the LHB gene in a male patient with hypogonadism and provided evidence that LHB nonsense mutation can cause selective LH deficiency. We reconfirmed hCG treatment may restore male fertility due to LHB mutation.

Testicular growth and development in puberty

PURPOSE OF REVIEW

To describe pubertal testicular growth in humans, changes in testicular cell populations that result in testicular growth, and the role of testosterone and gonadotrophins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in testicular growth. When human data were not available, studies in nonhuman primates and/or rodents were used as surrogates.

RECENT FINDINGS

Testicular growth in puberty follows a sigmoidal growth curve, with a large variation in timing of testicular growth and adult testicular volume. Testicular growth early in puberty is due to increase in Sertoli cell number and length of seminiferous tubules, whereas the largest and fastest growth results from the increase in the diameter of the seminiferous tubules first due to spermatogonial proliferation and then due to the expansion of meiotic and haploid germ cells. FSH stimulates Sertoli cell and spermatogonial proliferation, whereas LH/testosterone is mandatory to complete spermatogenesis. However, FSH and LH/testosterone work in synergy and are both needed for normal spermatogenesis.

SUMMARY

Testicular growth during puberty is rapid, and mostly due to germ cell expansion and growth in seminiferous tubule diameter triggered by androgens. Pre-treatment with FSH before the induction of puberty may improve the treatment of hypogonadotropic hypogonadism, but remains to be proven.

Leydig progenitor cells in fetal testis

Testicular Leydig cells play pivotal roles in masculinization of organisms by producing androgens. At least two distinct Leydig cell populations sequentially emerge in the mammalian testis. Leydig cells in the fetal testis (fetal Leydig cells) appear just after initial sex differentiation and induce masculinization of male fetuses. Although there has been a debate on the fate of fetal Leydig cells in the postnatal testis, it has been generally believed that fetal Leydig cells regress and are completely replaced by another Leydig cell population, adult Leydig cells. Recent studies revealed that gene expression patterns are different between fetal and adult Leydig cells and that the androgens produced in fetal Leydig cells are different from those in adult Leydig cells in mice. Although these results suggested that fetal and adult Leydig cells have distinct origins, several recent studies of mouse models support the hypothesis that fetal and adult Leydig cells arise from a common progenitor pool. In this review, we first provide an overview of previous knowledge, mainly from mouse studies, focusing on the cellular origins of fetal Leydig cells and the regulatory mechanisms underlying fetal Leydig cell differentiation. In addition, we will briefly discuss the functional differences of fetal Leydig cells between human and rodents. We will also discuss recent studies with mouse models that give clues for understanding how the progenitor cells in the fetal testis are subsequently destined to become fetal or adult Leydig cells.

A vital region for human glycoprotein hormone trafficking revealed by an LHB mutation

Glycoprotein hormones are complex hormonally active macromolecules. Luteinizing hormone (LH) is essential for the postnatal development and maturation of the male gonad. Inactivating Luteinizing hormone beta (LHB) gene mutations are exceptionally rare and lead to hypogonadism that is particularly severe in males. We describe a family with selective LH deficiency and hypogonadism in two brothers. DNA sequencing of LHB was performed and the effects of genetic variants on hormone function and secretion were characterized by mutagenesis studies, confocal microscopy and functional assays. A 20-year-old male from a consanguineous family had pubertal delay, hypogonadism and undetectable LH. A homozygous c.118_120del (p.Lys40del) mutation was identified in the patient and his brother, who subsequently had the same phenotype. Treatment with hCG led to pubertal development, increased circulating testosterone and spermatogenesis. Experiments in HeLa cells revealed that the mutant LH is retained intracellularly and showed diffuse cytoplasmic distribution. The mutated LHB heterodimerizes with the common alpha-subunit and can activate its receptor. Deletion of flanking glutamic acid residues at positions 39 and 41 impair LH to a similar extent as deletion of Lys40. This region is functionally important across all heterodimeric glycoprotein hormones, because deletion of the corresponding residues in hCG, follicle-stimulating hormone and thyroid-stimulating hormone beta-subunits also led to intracellular hormone retention. This novel LHB mutation results in hypogonadism due to intracellular sequestration of the hormone and reveals a discrete region in the protein that is crucial for normal secretion of all human glycoprotein hormones.

Clinical Applications of Gonadotropins in the Male

The pituitary gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) play a pivotal role in reproduction. The synthesis and secretion of gonadotropins are regulated by complex interactions among several endocrine, paracrine, and autocrine factors of diverse chemical structure. In men, LH regulates the synthesis of androgens by the Leydig cells, whereas FSH promotes Sertoli cell function and thereby influences spermatogenesis. Gonadotropins are complex molecules composed of two subunits, the α- and β-subunit, that are noncovalently associated. Gonadotropins are decorated with glycans that regulate several functions of the protein including folding, heterodimerization, stability, transport, conformational maturation, efficiency of heterodimer secretion, metabolic fate, interaction with their cognate receptor, and selective activation of signaling pathways. A number of congenital and acquired abnormalities lead to gonadotropin deficiency and hypogonadotropic hypogonadism, a condition amenable to treatment with exogenous gonadotropins. Several natural and recombinant preparations of gonadotropins are currently available for therapeutic purposes. The difference between natural and the currently available recombinant preparations (which are massively produced in Chinese hamster ovary cells for commercial purposes) mainly lies in the abundance of some of the carbohydrates that conform the complex glycans attached to the protein core. Whereas administration of exogenous gonadotropins in patients with isolated congenital hypogonadotropic hypogonadism is a well recognized therapeutic approach, their role in treating men with normogonadotropic idiopathic infertility is still controversial. This chapter concentrates on the main structural and functional features of the gonadotropin hormones and how basic concepts have been translated into the clinical arena to guide therapy for gonadotropin deficit in males.

A novel inactivating mutation of the LH/chorionic gonadotrophin receptor with impaired membrane trafficking leading to Leydig cell hypoplasia type 1

OBJECTIVE

The LH/chorionic gonadotrophin receptor (LHCGR) is a G protein-coupled receptor (GPCR) that plays a central role in male sexual differentiation, regulation of ovarian follicular maturation, ovulation and maintenance of corpus luteum and pregnancy, as well as maintenance of testicular testosterone production. Mutations in the LHCGR gene are very rare. The aim of this work was to study the clinical and molecular characteristics of a rare familial LHCGR mutation.

METHODS

Five affected members of a family, including a phenotypically female, but genotypically male (46,XY), patient with Leydig cell hypoplasia type 1 and four genotypically female siblings with reproductive abnormalities, were studied genetically. Cell trafficking studies as well as signalling studies of mutated receptor were performed.

RESULTS

The five affected patients were all homozygous for a novel mutation in the LHCGR gene, a deletion of guanine in position 1850 (1850delG). This resulted in a frameshift affecting most of the C-terminal intracellular domain. In vitro studies demonstrated that the 1850delG receptor was completely incapable of transit to the cell membrane, becoming trapped within the endoplasmic reticulum. This could not be rescued by small-molecule agonist treatment or stimulated intracellularly by co-expression of a yoked human chorionic gonadotrophin.

CONCLUSIONS

This novel LHCGR mutation leads to complete inactivation of the LHCGR receptor due to trafficking and signalling abnormalities, which improves our understanding of the impact of the affected structural domain on receptor trafficking and function.

Glomerular hyperfiltration in hypogonadotropic hypogonadic patients: Overlooking a cache?

PURPOSE

To investigate renal function in idiopathic hypogonadotropic hypogonadic (IHH) patients by measuring glomerular filtration rate (GFR) using modification of diet in renal disease formula, and determine whether there is any relationship between GFR and testosterone levels.

METHODS

Thirty-three patients with IHH and 37 healthy control subjects participated in this study.

RESULTS

The IHH group showed statistically significant higher GFR and proteinuria with respect to the control group (163.1 ± 46.9 to 117.9 ± 30.5 mL/min, p < 0.001; 0.2 ± 0.1 to 0.08 ± 0.02 mg/dL, p = 0.041, respectively). Uric acid and creatinine levels were statistically lower than in the control group (4.6 ± 0.5-3.6 ± 0.9 mg/dL, p = 0.02; 0.7 ± 0.2 to 0.9 ± 0.2 mg/dL, p < 0.001, respectively). Hyperfiltration positively correlated with IHH in multivariate linear regression analyses (β = 0.591, p < 0.001). In addition, in the IHH group, we found that the GFR increased independently of body mass index and age.

CONCLUSION

Our study confirms that low testosterone in IHH patients is associated with glomerular hyperfiltration. Patients with IHH should be carefully monitored with respect to their GFR.

Morphological and functional maturation of Leydig cells: from rodent models to primates

BACKGROUND

Leydig cells (LC) are the sites of testicular androgen production. Development of LC occurs in the testes of most mammalian species as two distinct growth phases, i.e. as fetal and pubertal/adult populations. In primates there are indications of a third neonatal growth phase. LC androgen production begins in embryonic life and is crucial for the intrauterine masculinization of the male fetal genital tract and brain, and continues until birth after which it rapidly declines. A short post-natal phase of LC activity in primates (including human) termed 'mini-puberty' precedes the period of juvenile quiescence. The adult population of LC evolves, depending on species, in mid- to late-prepuberty upon reawakening of the hypothalamic-pituitary-testicular axis, and these cells are responsible for testicular androgen production in adult life, which continues with a slight gradual decline until senescence. This review is an updated comparative analysis of the functional and morphological maturation of LC in model species with special reference to rodents and primates.

METHODS

Pubmed, Scopus, Web of Science and Google Scholar databases were searched between December 2012 and October 2014. Studies published in languages other than English or German were excluded, as were data in abstract form only. Studies available on primates were primarily examined and compared with available data from specific animal models with emphasis on rodents.

RESULTS

Expression of different marker genes in rodents provides evidence that at least two distinct progenitor lineages give rise to the fetal LC (FLC) population, one arising from the coelomic epithelium and the other from specialized vascular-associated cells along the gonad-mesonephros border. There is general agreement that the formation and functioning of the FLC population in rodents is gonadotrophin-responsive but not gonadotrophin-dependent. In contrast, although there is in primates some controversy on the role of gonadotrophins in the formation of the FLC population, there is consensus about the essential role of gonadotrophins in testosterone production. Like the FLC population, adult Leydig cells (ALC) in rodents arise from stem cells, which have their origin in the fetal testis. In contrast, in primates the ALC population is thought to originate from FLC, which undergo several cycles of regression and redifferentiation before giving rise to the mature ALC population, as well as from differentiation of stem cells/precursor cells. Despite this difference in origin, both in primates and rodents the formation of the mature and functionally active ALC population is critically dependent on the pituitary gonadotrophin, LH. From studies on rodents considerable knowledge has emerged on factors that are involved besides LH in the regulation of this developmental process. Whether the same factors also play a role in the development of the mature primate LC population awaits further investigation.

CONCLUSION

Distinct populations of LC develop along the life span of males, including fetal, neonatal (primates) and ALC. Despite differences in the LC lineages of rodents and primates, the end product is a mature population of LC with the main function to provide androgens necessary for the maintenance of spermatogenesis and extra-gonadal androgen actions.

Genetic Models for the Study of Luteinizing Hormone Receptor Function

The luteinizing hormone/chorionic gonadotropin receptor (LHCGR) is essential for fertility in men and women. LHCGR binds luteinizing hormone (LH) as well as the highly homologous chorionic gonadotropin. Signaling from LHCGR is required for steroidogenesis and gametogenesis in males and females and for sexual differentiation in the male. The importance of LHCGR in reproductive physiology is underscored by the large number of naturally occurring inactivating and activating mutations in the receptor that result in reproductive disorders. Consequently, several genetically modified mouse models have been developed for the study of LHCGR function. They include targeted deletion of LH and LHCGR that mimic inactivating mutations in hormone and receptor, expression of a constitutively active mutant in LHCGR that mimics activating mutations associated with familial male-limited precocious puberty and transgenic models of LH and hCG overexpression. This review summarizes the salient findings from these models and their utility in understanding the physiological and pathological consequences of loss and gain of function in LHCGR signaling.

Hormonal therapy for non-obstructive azoospermia: basic and clinical perspectives

Microdissection testicular sperm extraction (micro-TESE) combined with intracytoplasmic sperm injection is a standard therapeutic option for patients with non-obstructive azoospermia (NOA). Hormonal treatment has been believed to be ineffective for NOA because of high gonadotropin levels; however, several studies have stimulated spermatogenesis before or after micro-TESE by using anti-estrogens, aromatase inhibitors, and gonadotropins. These results remain controversial; however, it is obvious that some of the patients showed a distinct improvement in sperm retrieval by micro-TESE, and sperm was observed in the ejaculates of a small number of NOA patients. One potential way to improve spermatogenesis is by optimizing the intratesticular testosterone (ITT) levels. ITT has been shown to be increased after hCG-based hormonal therapy. The androgen receptor that is located on Sertoli cells plays a major role in spermatogenesis, and other hormonal and non-hormonal factors may also be involved. Before establishing a new hormonal treatment protocol to stimulate spermatogenesis in NOA patients, further basic investigations regarding the pathophysiology of spermatogenic impairment are needed. Gaining a better understanding of this issue will allow us to tailor a specific treatment for each patient.

The genetics of Mullerian aplasia

Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome consists of Mullerian aplasia with or without other anomalies, most commonly renal and skeletal. The genetic etiology of MRKH syndrome is unknown for most patients, but supportive evidence exists for heterozygous mutations in WNT4, LHX1, and HNF1B. Chromosomal microarray analyses have demonstrated chromosomal regions with copy number variants in multiple patients - deletions in17q12 and 16p11.2, and either deletions or duplications in 22q11.2. Genomic analyses of expression and methylation have also suggested potential molecular pathways. Positional cloning in MRKH patients with chromosomal rearrangements and exome sequencing are likely to result in new genes. Although some single gene defects and copy number variant regions have been identified, the molecular basis for the vast majority of MRKH remains unknown.

Hypogonadotropic hypogonadism: new identification of testicular blood flow and varicocele after treatment with gonadotropins

OBJECTIVE

To investigate testicular changes in patients with hypogonadotropic hypogonadism (HH) after treatment with gonadotropins.

DESIGN

Patients with HH were investigated and followed before and after treatment.

SETTING

Urology and andrology clinic of a teaching hospital.

PATIENT(S)

Consecutive male patients with diagnosed HH.

INTERVENTION(S)

All patients were treated with gonadotropins during the study period and later.

MAIN OUTCOME MEASURE(S)

The hormonal status and scrotal color Doppler ultrasound (CDUS) of patients was recorded before and after treatment.

RESULT(S)

Twenty-six patients with HH (ages 18-43 years) were followed for 8-29 months. After treatment, serum T and secondary sex characters improved in all and spermatogenesis developed in 61.5% of patients. Before treatment, testicular (intraparenchymal blood flow) was undetectable in all and barely detectable in three patients. This improved significantly to 4.53±5.44 and 4.27±4.97 cm/second, respectively, after treatment. Subcapsular arterial flow and testicular size also improved significantly. Similarly, after treatment, transverse epididymal diameter (TED) increased significantly. At baseline, no patient had detectable varicocele on CDUS. After treatment, varicocele was demonstrable in 23% of patients. This finding was further evaluated retrospectively from our 76 HH patient files. None of them had varicocele before treatment, but after treatment 19.73% were found to have varicocele.

CONCLUSION(S)

Patients with HH responded to gonadotropins by improvement in testicular blood flow and increase in TED. In some patients, varicocele was found to develop after treatment.

Congenital hypogonadotropic hypogonadism and Kallmann syndrome as models for studying hormonal regulation of human testicular endocrine functions

Men with Kallmann syndrome (KS) and those with congenital isolated hypogonadotropic hypogonadism with normal olfaction share a chronic, usually profound deficit, in FSH and LH, the two pituitary gonadotropins. Many studies indicate that this gonadotropin deficiency is already present during fetal life, thus explaining the micropenis, cryptorchidism and marked testicular hypotrophy already present at birth. In addition, neonatal activation of gonadotropin secretion is compromised in boys with severe CHH/Kallmann, preventing the first phase of postnatal testicular activation. Finally, CHH is characterized by the persistence, in the vast majority of cases, of gonadotropin deficiency at the time of puberty and during adulthood. This prevents the normal pubertal testicular reactivation required for physiological sex steroid and testicular peptide production, and for spermatogenesis. CHH/KS thus represents a pathological paradigm that can help to unravel, in vivo, the role of each gonadotropin in human testicular exocrine and endocrine functions at different stages of development. Recombinant gonadotropins with pure LH or FSH activity have been used to stimulate Leydig's cells and Sertoli's cells, respectively, and thereby to clarify their paracrine interaction in vivo. The effects of these pharmacological probes can be assessed by measuring the changes they provoke in circulating testicular hormone concentrations. This review discusses the impact of chronic gonadotropin deficiency on the endocrine functions of the interstitial compartment, which contains testosterone-, estradiol- and INSL3-secreting Leydig's cells. It also examines the regulation of inhibin B and anti-Mullerian hormone (AMH) secretion in the seminiferous tubules, and the insights provided by studies of human testicular stimulation with recombinant gonadotropins, used either individually or in combination.

Endocrine control of spermatogenesis: Role of FSH and LH/ testosterone

Evaluation of testicular functions (production of sperm and androgens) is an important aspect of preclinical safety assessment and testicular toxicity is comparatively far more common than ovarian toxicity. This chapter focuses (1) on the histological sequelae of disturbed reproductive endocrinology in rat, dog and nonhuman primates and (2) provides a review of our current understanding of the roles of gonadotropins and androgens. The response of the rodent testis to endocrine disturbances is clearly different from that of dog and primates with different germ cell types and spermatogenic stages being affected initially and also that the end-stage spermatogenic involution is more pronounced in dog and primates compared to rodents. Luteinizing hormone (LH)/testosterone and follicle-stimulating hormone (FSH) are the pivotal endocrine factors controlling testicular functions. The relative importance of either hormone is somewhat different between rodents and primates. Generally, however, both LH/testosterone and FSH are necessary for quantitatively normal spermatogenesis, at least in non-seasonal species.

Pituitary gonadotropins and autoimmunity

Autoimmune disease occurs when the body produces an inappropriate immune response against its own tissues producing antibodies, called autoantibodies, reacting to specific antigens. Studies regarding the presence of an autoimmune process specifically involving gonadotropins date from over than 20 years ago, when antibodies to gonadotropic-secreting cells were found by immunofluorescence in sera from a group of patients affected by cryptorchidism. Later on, antibodies detected by the same technique, and directed to the same cells were also found at high titer in sera from patients affected by hypogonadotropic hypogonadism, Kallmann's syndrome, lymphocytic hypophysitis with isolated gonadotropin deficiency, as well as autoimmune polyendocrine syndrome. Concerning the autoimmune target/s within the gonadotropic cells, rarely autoantibodies were found labeling gonadotropins while in a large number of cases, auto-antigens remained to be identified. Since pituitary gonadotropins are fundamental for the sexual maturity and reproductive mechanisms, patients with infertility were largely investigated by enzyme-linked immunosorbent assay for the presence of circulating antibodies likely interfering with gonadotropin activity. In infertile women, autoantibodies to gonadotropins were found related to ovarian autoimmunity, ovarian disorders that cause infertility and also associated with in vitro fertilization treatments. In infertile men, autoantibodies to gonadotropins may alter the testicular spermatogenesis and cause apoptosis of the spermatogenic cells. In conclusion, circulating antibodies were found labeling gonadotropic cells and/or gonadotropins, and in both cases they could create dysfunctions in gonadotropin related mechanism. The intriguing question of what can cause the production of such autoantibodies is not clear yet.

Luteinizing hormone and human chorionic gonadotropin: distinguishing unique physiologic roles

Luteinizing hormone (LH) and human chorionic gonadotropin (hCG) are integral components of the hypothalamic-pituitary-gonadal axis, which controls sexual maturation and functionality. In the absence of signaling through their shared receptor, fetal sexual differentiation and post-natal development cannot proceed normally. Although they share a high degree of homology, the physiologic roles of these hormones are unique, governed by differences in expression pattern, biopotency and regulation. Whereas LH is a key regulator of gonadal steroidogenesis and ovulation, hCG is predominantly active in pregnancy and fetal development. Emerging evidence has revealed endogenous functions not previously ascribed to hCG, including participation in ovulation and fertilization, implantation, placentation and other activities in support of successful pregnancy. Spontaneous and induced mutations in LH, hCG and their mutual receptor have contributed substantially to our understanding of reproductive development and function. The lack of naturally occurring, functionally significant mutations in the β-subunit of hCG reinforce its putative role in establishment of pregnancy. Rescue of reproductive abnormalities resulting from aberrant gonadotropin signaling is possible in certain clinical contexts, depending on the nature of the underlying defect. By understanding the physiologic roles of LH and hCG in normal and pathologic states, we may better harness their diagnostic, prognostic and therapeutic potential.

Reproduction, smell, and neurodevelopmental disorders: genetic defects in different hypogonadotropic hypogonadal syndromes

The neuroendocrine control of reproduction in mammals is governed by a neural hypothalamic network of nearly 1500 gonadotropin-releasing hormone (GnRH) secreting neurons that modulate the activity of the reproductive axis across life. Congenital hypogonadotropic hypogonadism (HH) is a clinical syndrome that is characterized by partial or complete pubertal failure. HH may result from inadequate hypothalamic GnRH axis activation, or a failure of pituitary gonadotropin secretion/effects. In man, several genes that participate in olfactory and GnRH neuronal migration are thought to interact during the embryonic life. A growing number of mutations in different genes are responsible for congenital HH. Based on the presence or absence of olfaction dysfunction, HH is divided in two syndromes: HH with olfactory alterations [Kallmann syndrome (KS)] and idiopathic hypogonadotropic hypogonadism (IHH) with normal smell (normosmic IHH). KS is a heterogeneous disorder affecting 1 in 5000 males, with a three to fivefold of males over females. KS is associated with mutations in KAL1, FGFR1/FGF8, FGF17, IL17RD, PROK2/PROKR2, NELF, CHD7, HS6ST1, FLRT3, SPRY4, DUSP6, SEMA3A, NELF, and WDR11 genes that are related to defects in neuronal migration. These reproductive and olfactory deficits include a variable non-reproductive phenotype, including sensorineural deafness, coloboma, bimanual synkinesis, craniofacial abnormalities, and/or renal agenesis. Interestingly, defects in PROKR2, FGFR1, FGF8, CHD7, DUSP6, and WDR11 genes are also associated with normosmic IHH, whereas mutations in KISS1/KISSR, TAC3/TACR3, GNRH1/GNRHR, LEP/LEPR, HESX1, FSHB, and LHB are only present in patients with normosmic IHH. In this paper, we summarize the reproductive, neurodevelopmental, and genetic aspects of HH in human pathology.

Spreading the clinical window for diagnosing fetal-onset hypogonadism in boys

In early fetal development, the testis secretes - independent of pituitary gonadotropins - androgens and anti-Müllerian hormone (AMH) that are essential for male sex differentiation. In the second half of fetal life, the hypothalamic-pituitary axis gains control of testicular hormone secretion. Follicle-stimulating hormone (FSH) controls Sertoli cell proliferation, responsible for testis volume increase and AMH and inhibin B secretion, whereas luteinizing hormone (LH) regulates Leydig cell androgen and INSL3 secretion, involved in the growth and trophism of male external genitalia and in testis descent. This differential regulation of testicular function between early and late fetal periods underlies the distinct clinical presentations of fetal-onset hypogonadism in the newborn male: primary hypogonadism results in ambiguous or female genitalia when early fetal-onset, whereas it becomes clinically undistinguishable from central hypogonadism when established later in fetal life. The assessment of the hypothalamic-pituitary-gonadal axis in male has classically relied on the measurement of gonadotropin and testosterone levels in serum. These hormone levels normally decline 3-6 months after birth, thus constraining the clinical evaluation window for diagnosing male hypogonadism. The advent of new markers of gonadal function has spread this clinical window beyond the first 6 months of life. In this review, we discuss the advantages and limitations of old and new markers used for the functional assessment of the hypothalamic-pituitary-testicular axis in boys suspected of fetal-onset hypogonadism.

Central hypogonadotropic hypogonadism: genetic complexity of a complex disease

Central hypogonadotropic hypogonadism (CHH) is an emerging pathological condition frequently associated with overweight, metabolic syndrome, diabetes, and midline defects. The genetic mechanisms involve mutations in at least twenty-four genes regulating GnRH neuronal migration, secretion, and activity. So far, the mechanisms underlying CHH, both in prepubertal and in adulthood onset forms, remain unknown in most of the cases. Indeed, all detected gene variants may explain a small proportion of the affected patients (43%), indicating that other genes or epigenetic mechanisms are involved in the onset of CHH. The aim of this review is to summarize the current knowledge on genetic background of CHH, organizing the large amount of data present in the literature in a clear and concise manner, to produce a useful guide available for researchers and clinicians.

Male hypogonadism: an extended classification based on a developmental, endocrine physiology-based approach

Normal testicular physiology results from the integrated function of the tubular and interstitial compartments. Serum markers of interstitial tissue function are testosterone and insulin-like factor 3 (INSL3), whereas tubular function can be assessed by sperm count, morphology and motility, and serum anti-Müllerian hormone (AMH) and inhibin B. The classical definition of male hypogonadism refers to testicular failure associated with androgen deficiency, without considering potential deficiencies in germ and Sertoli cells. Furthermore, the classical definition does not consider the fact that low basal serum testosterone cannot be equated to hypogonadism in childhood, because Leydig cells are normally quiescent. A broader clinical definition of hypogonadism that could be applied to male patients in different periods of life requires a comprehensive consideration of the physiology of the hypothalamic-pituitary-testicular axis and its disturbances along development. Here we propose an extended classification of male hypogonadism based on the pathophysiology of the hypothalamic-pituitary-testicular axis in different periods of life. The clinical and biochemical features of male hypogonadism vary according to the following: (i) the level of the hypothalamic-pituitary-testicular axis primarily affected: central, primary or combined; (ii) the testicular cell population initially impaired: whole testis dysfunction or dissociated testicular dysfunction, and: (iii) the period of life when the gonadal function begins to fail: foetal-onset or postnatal-onset. The evaluation of basal testicular function in infancy and childhood relies mainly on the assessment of Sertoli cell markers (AMH and inhibin B). Hypergonadotropism should not be considered a sine qua non condition for the diagnosis of primary hypogonadism in childhood. Finally, the lack of elevation of gonadotropins in adolescents or adults with primary gonadal failure is indicative of a combined hypogonadism involving the gonads and the hypothalamic-pituitary axis.

Hypogonadism in a patient with two novel mutations of the luteinizing hormone β-subunit gene expressed in a compound heterozygous form

CONTEXT

LH gene mutations are rare; only four mutations have been described. The affected individuals are hypogonadal.

PATIENT

We describe the clinical features of a 31-yr-old man who presented with delayed puberty and azoospermia and was found to have hypogonadism associated with an absence of circulating LH.

MAIN OUTCOME MEASURES AND RESULTS

The patient had a 12-bp deletion in exon 2 in the LH β-subunit gene and a mutation of the 5' splice site IVS2+1G→T in the same gene present in a compound heterozygous state. The first mutation predicts a deletion of four leucines of the hydrophobic core of the signal peptide. The second mutation disrupts the splicing of mRNA, generating a gross abnormality in the processing. The patient's heterozygous parents were clinically normal. The phenotype of a 16-yr-old sister of the proband, carrying the same mutations, was characterized by normal pubertal development and oligomenorrhea.

CONCLUSION

This report unravels two novel mutations of the LH gene critical for synthesis and activity of the LH molecule. The insight gained from the study is that normal pubertal maturation in women can occur in a state of LH deficiency, whereas LH is essential for maturation of Leydig cells and thus steroidogenesis, puberty, and spermatogenesis in man. These mutations should be considered in girls and boys with selective deficiency of LH.

Neonatal gonadotropin therapy in male congenital hypogonadotropic hypogonadism

Congenital hypogonadotropic hypogonadism (CHH) causes pubertal failure and infertility in both women and men due to partial or total secretory failure of the two pituitary gonadotropins lutropin (LH) and follitropin (FSH) during periods of physiological activation of the gonadotropic axis. Men and women with CHH frequently seek treatment for infertility after hypogonadism therapy. Some etiologies, such as autosomal dominant or X-linked Kallmann syndrome, raise the question of hereditary transmission, leading to increasing demands for genetic counseling and monitoring of medically assisted pregnancies. Diagnosis and treatment of newborn boys is, therefore, becoming an increasingly important issue. In male individuals with complete forms of CHH, the antenatal and neonatal gonadotropin deficit leads to formation of a micropenis and cryptorchidism, which could undermine future sexual and reproductive functions. Standard treatments, usually started after the age of puberty, often only partially correct the genital abnormalities and spermatogenesis. The aim of this Review is to examine the possible additional benefits of neonatal gonadotropin therapy in male patients with CHH. Encouraging results of neonatal therapy, together with a few reports of prepubertal treatment, support the use of this novel therapeutic strategy aimed at improving sexual and reproductive functions in adulthood.

Genomics and genetics of gonadotropin beta-subunit genes: Unique FSHB and duplicated LHB/CGB loci

The follicle stimulating hormone (FSH), luteinizing hormone (LH) and chorionic gonadotropin (HCG) play a critical role in human reproduction. Despite the common evolutionary ancestry and functional relatedness of the gonadotropin hormone beta (GtHB) genes, the single-copy FSHB (at 11p13) and the multi-copy LHB/CGB genes (at 19q13.32) exhibit locus-specific differences regarding their genomic context, evolution, genetic variation and expressional profile. FSHB represents a conservative vertebrate gene with a unique function and it is located in a structurally stable gene-poor region. In contrast, the primate-specific LHB/CGB gene cluster is located in a gene-rich genomic context and demonstrates an example of evolutionary young and unstable genomic region. The gene cluster is shaped by a constant balance between selection that acts on specific functions of the loci and frequent gene conversion events among duplicons. As the transcription of the GtHB genes is rate-limiting in the assembly of respective hormones, the genomic and genetic context of the FSHB and the LHB/CGB genes largely affects the profile of the hormone production.

Steroidogenesis in the fetal testis and its susceptibility to disruption by exogenous compounds

Masculinization depends on adequate production of testosterone by the fetal testis within a specific "masculinization programming window." Disorders resulting from subtle deficiencies in this process are common in humans, and environmental exposures/lifestyle could contribute causally because common therapeutic and environmental compounds can affect steroidogenesis. This evidence derives mainly from rodent studies, but because there are major species differences in regulation of steroidogenesis in the fetal testis, this may not always be a guide to potential effects in the human. In addition to direct study of the effects of compounds on steroidogenesis, information also derives from study of masculinization disorders that result from mutations in genes in pathways regulating steroidogenesis. This review addresses this issue by critically reviewing the comparative timing of production and regulation of steroidogenesis in the fetal testis of humans and of rodents and its susceptibility to disruption; where there is limited information for the fetus, evidence from effects on steroidogenesis in the adult testis is considered. There are a number of fundamental regulatory differences between the human and rodent fetal testis, most notably in the importance of paracrine vs. endocrine drives during masculinization such that inactivating LH receptor mutations block masculinization in humans but not in rodents. Other large differences involve the steroidogenic response to estrogens and GnRH analogs and possibly phthalates, whereas for other compounds there may be differences in sensitivity to disruption (ketoconazole). This comparison identifies steroidogenic targets that are either vulnerable (mitochondrial cholesterol transport, CYP11A, CYP17) or not (cholesterol uptake) to chemical interference.

Maternal smoking and developmental changes in luteinizing hormone (LH) and the LH receptor in the fetal testis

CONTEXT

The LH receptor (LHCGR) drives fetal testosterone secretion, which is vital for human masculinization. Maternal smoking is associated with defective masculinization, but the relationship between smoking, tropic hormones, testosterone, and functional LHCGR expression is poorly understood.

OBJECTIVE

This study aimed to investigate developmental changes in fetal gonadotropins, human chorionic gonadotropin (hCG), and expression of fetal testicular LHCGR isoforms and the effects of maternal cigarette smoking.

DESIGN

We conducted an observational study of the male fetus, comparing pregnancies in which the mothers did or did not smoke.

SETTING

The study was conducted at the Universities of Aberdeen and Glasgow.

PATIENTS/PARTICIPANTS

Testes and blood were collected from 54 morphologically normal human male fetuses of women undergoing elective termination of normal second-trimester pregnancies.

MAIN OUTCOME MEASURES

We measured circulating testosterone, hCG, LH, prolactin, FSH, and testicular LHCGR isoform expression.

RESULTS

Fetal testosterone and hCG, but not LH, significantly declined between 11 and 19 wk gestation with no significant change in testicular responsiveness. The proportion of nonfunctional LHCGR transcript in fetal testes was 2.3-fold lower than in adults. Fetal hCG was reduced 38% (P = 0.021) and the ratio of inactive vs. active LHCGR isoforms lowered by smoking.

CONCLUSIONS

Falling second-trimester fetal testosterone is probably due to declining maternal hCG because Leydig cell LH/hCG responsiveness remains constant. Although maternal cigarette smoking reduces fetal hCG, the ratio of inactive LHCGR isoforms is reduced and gonadotropin drive maintains testosterone production near control levels. The lower relative abundance of inactive isoforms compared with the adult testis reflects the importance of LHCGR.

Normal spermatogenesis in a man with mutant luteinizing hormone

Men with mutations in LHB, the gene encoding the beta subunit of luteinizing hormone (LHB), have azoospermia with absent or few fetal Leydig cells. We report a mutation in LHB in a man and his sister. The man presented with absence of virilization, undetectable luteinizing hormone, and a low serum testosterone level. He had complete spermatogenesis with a normal sperm count. The mutant luteinizing hormone had a low level of partial activity in vitro. We concluded that the residual luteinizing hormone activity, resulting in the expression of steroidogenic enzymes in few mature Leydig cells producing small amounts of intratesticular testosterone (20.2 ng per gram), was sufficient for complete and quantitatively normal spermatogenesis.

[Congenital hypogonadotropic hypogonadism]

Congenital hypogonadotropic hypogonadism is defined by reduced steroid hormone synthesis and secretion due to low LH and FSH secretion. It is a rare disease with an unknown prevalence (about 1/5000). It results from a fetal defect in GnRH neuron migration, a defect of pituitary development or from a functional defect of the hypothalamopituitary axis between GnRH neurons and gonadotropic cells. The diagnosis should be considered at birth in males with micropenis, during adolescence in case of delayed puberty or absent puberty, and during adulthood in case of infertility. It may be restricted to the gonadotropic axis, combined with other endocrine system defects or be part of a complex syndrome. Several gene defects have now been described. Molecular studies should be performed to confirm the diagnosis and to help provide appropriate genetic counseling. Treatment to induce puberty should be provided at adolescence, followed by hormonal substitution treatment during adulthood. Specific infertility treatment may also be proposed but patients with the dominant form of gonadotropic deficiency should be informed of the risk of transmission.