Clinical and Hormonal Features of a Male Adolescent with Congenital Isolated Follicle-Stimulating Hormone Deficiency

Clinical and genetic analysis of an isolated follicle-stimulating hormone deficiency female patient

OBJECTIVE

To characterize the clinical features of a female patient with isolated follicle-stimulating hormone (FSH) deficiency and to investigate the underlying mechanisms of FSH inactivation.

METHODS

The proband was a 29-year-old woman with primary amenorrhea, impaired pubertal development, and infertility. Subsequently, reproductive endocrine was screened. DNA sequencing was conducted for the identification of FSHβ mutation. RT-PCR, western blots, in vitro immunometric assay, and bioassay were performed to confirm the impact of the mutation on FSH expression and biological activity. Molecular model consisting of FSHα and mutant FSHβ subunit was built for the structural analysis of FSH protein.

RESULTS

The evaluation of reproductive endocrine revealed undetectable basal and GnRH-stimulated serum FSH. Sequencing of the FSHβ gene identified a homozygous nonsense mutation at codon 97 (Arg97X). RT-PCR and western blot analysis revealed the mutation Arg97X did not affect FSHβ mRNA and protein expression. But in vitro immunometric assay and bioassay demonstrated the production of normal bioactive FSH protein was disturbed by the mutation Arg97X. Structural analysis showed the surface structure of the resulting mutant FSH presented with lock-and-key, mosaic binding pattern, while the native structure was an encircling binding mode.

CONCLUSION

The mutation Arg97X could disturb structural stability of the resulting FSH protein consisting of FSHα and mutant FSHβ subunit, which may lead to FSH deficiency.

Isolated follicle-stimulating hormone (FSH) deficiency in two infertile men without FSH β gene mutation: Case report and literature review

OBJECTIVE

Congenital FSH deficiency is an exceptional cause of male infertility most often attributed to FSH β gene mutations. The few published cases report azoospermia, severe testicular hypotrophy and normal testosterone levels associated with normal virilization. We report the exploration of two young men aged 26 and 27 years with severe sperm abnormalities, moderate testicular hypotrophy and isolated FSH deficiency.

METHODS

Several FSH, LH, total testosterone and inhibin B assays and FSH β gene sequencing were performed.

RESULTS

FSH was almost undetectable at baseline and poorly responsive to GnRH test, whereas LH was normal at baseline and increased after GnRH test. Testosterone levels were within the adult range, while inhibin B levels were upper-normal to high. No FSH β gene mutations were found. Exogenous FSH treatment was followed by spontaneous pregnancy in one case and required intra-cytoplasmic sperm injection (ICSI) in the other.

CONCLUSIONS

The paradoxical high levels of inhibin B reflect the presence of functional Sertoli cells and may explain the isolated FSH deficiency. An intra-gonadal factor stimulating inhibin B secretion is discussed.

FSH β-subunit mutations in two sisters: the first report from the Indian sub-continent and review of previous cases

Isolated FSH deficiency due to mutations in the gene for β-subunit of FSH is an extremely rare autosomal recessive disease of which only eleven cases have been reported so far. The clinical features include absent breast development and primary amenorrhea in females and azoospermia with normal testosterone levels in males. In this study we report two Kashmiri sisters born to native Kashmiri consanguineous parents with failure of onset of puberty. Hormonal evaluation revealed undetectable serum FSH and estradiol and high LH. Genetic analysis of FSH β-gene identified one nonsense mutation (c.343C > T:p. Arg115Stop) in exon 3. The two sisters were homozygous for this nonsense mutation while the parents were heterozygous. Incorporation of a stop codon at 115 codon position is predicted to result in the formation of truncated FSH β protein, lacking 14 amino acid from the carboxy-terminus (p.Arg115Stop). Very recently, this same mutation was reported for the first time in a Chinese male. Ours is the first ever report of any FSH β-subunit mutation from the Indian sub-continent and this particular mutation in any female from anywhere in the world. We conclude and emphasize that this diagnosis should be considered in girls with delayed puberty and selective deficiency of FSH.

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.

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.