Primary amenorrhoea and infertility due to a mutation in the beta-subunit of follicle-stimulating hormone

Luteinizing hormone beta mutation and hypogonadism in men and women

Selective luteinizing hormone deficiency due to mutations in the luteinizing hormone beta-subunit gene (LHB) is a rare cause of hypogonadism. We describe the clinical features of a consanguineous family in which three siblings, two men and one woman, had hypogonadism related to isolated luteinizing hormone deficiency. These subjects have a newly discovered homozygous mutation of a 5' splice site in LHB: IVS2+1G-->C. This mutation disrupts the splicing of messenger RNA (mRNA), generating a gross abnormality in the processing of the luteinizing hormone beta-subunit mRNA, which abrogates the secretion of luteinizing hormone. We also determined that the female phenotype of this LHB mutation is characterized by normal pubertal development, secondary amenorrhea, and infertility.

Branched chain alpha-keto acid dehydrogenase, E1-beta subunit gene is associated with premature ovarian failure

Genetic variants of the human branched chain alpha-keto acid dehydrogenase, E1-beta subunit (BCKDHB) gene were identified and they have been associated with premature ovarian failure (POF). Reconstructed haplotype from these variants was also associated with POF.

Ovulation induction management of PCOS

Ovulation induction is the principal infertility treatment for women with polycystic ovarian syndrome (PCOS). Among PCOS patients who are overweight or obese, weight loss is the most physiologic method of inducing ovulation. For women in whom weight loss is not possible, or for lean women with PCOS, clomiphene citrate is an effective first-line method of ovulation induction. In clomiphene-resistant women, alternative treatments include adjunctive metformin or dexamethasone, aromatase inhibitors, or ovarian drilling. If there is no pregnancy despite several cycles of successful ovulation induction, gonadotropin treatment should be considered, in which case in vitro fertilization is recommended as the safest and most effective strategy.

Genetic insights into human isolated gonadotropin deficiency

The identification of naturally occurring genetic mutations has provided unique insight into the current knowledge of the human hypothalamic-pituitary-gonadal axis. In the past decade, several monogenic causes have been reported in patients with isolated gonadotropin deficiency. Kallmann Syndrome is a clinically and genetically heterogeneous disorder, characterized by isolated hypogonadotropic hypogonadism and anosmia or hyposmia. To date, loss-of-function mutations in the genes encoding anosmin-1 (KAL1) and fibroblast growth factor receptor 1 (FGFR1) have been described in the X-linked and autosomal dominant forms of this syndrome, respectively. More recently, several heterozygous, homozygous or compound heterozygous mutations in the G protein-coupled prokineticin receptor-2 (PROKR2) and one of its ligands, prokineticin-2 (PROK2) were described in Kallmann syndrome. In addition, complex genetic transmission (digenic inheritance) was recently demonstrated in this condition. Regarding isolated hypogonadotropic hypogonadism without olfactory abnormalities, loss-of-function mutations in the Gonadotropin-releasing hormone (GnRH) receptor (GnRH-R) or the G-protein coupled receptor 54 (GPR54) genes, both encoding transmembrane receptors, have been described, as well as FGFR1 mutations. Finally, mutations of the beta sub-units of LH and FSH have been described in patients with selective gonadotropin deficiency. We review the role of these distinct genetic factors in human isolated hypogonadotropic hypogonadism.

Gonadotrophin resistance

Gonadotrophin resistance is caused by inactivating mutations in receptors (Rs) of the two gonadotrophins, i.e. luteinizing hormone (LH) and follicle-stimulating hormone (FSH), presenting as hypergonadotrophic hypogonadism and infertility/subfertility in both sexes. These conditions are extremely rare, but must be kept in mind upon differential diagnosis of disorders of sexual maturation, hypogonadism and infertility. In 46,XY individuals inactivation of LHR causes a disturbance in male-type sexual differentiation that ranges from male pseudohermaphroditism (complete lack of genital masculinization) to mild conditions such as cryptorchidism and hypospadias, depending on completeness of the receptor inactivation. In women, the phenotype is milder, presenting mainly as anovulatory amenorrhoea and hypo-oestrogenization. Inactivation of FSHR causes in otherwise normally masculinized men small testis size and variably reduced spermatogenesis, but not azoospermia or absolute infertility. In women the phenotype is more severe, with primary or early secondary amenorrhoea, arrested follicular maturation and anovulatory infertility. Incomplete forms with milder phenotype and partial responsiveness to FSH have also been described. Although gonadotrophin resistance is a very rare condition, its correct diagnosis is important for the selection of adequate treatment.

Premature ovarian failure

PURPOSE OF REVIEW

To summarize current knowledge about premature ovarian failure (POF) with an emphasis on recent developments regarding its management.

RECENT FINDINGS

The incidence of POF is increasing largely due to improved survival rates of cancer patients treated with radiation and chemotherapy. Delayed diagnosis and management of POF leads to suboptimal outcomes. Anticipation and early detection of this condition in high-risk women by means of ovarian function testing, followed by early institution of appropriate management could improve outcomes. Choice of strategies should vary depending on the age of onset, associated symptoms and fertility aspirations of the individual, and should change with the patient's advancing age.

SUMMARY

Early assessment of the individual's risk of developing POF, development of a strategic management plan, and timely commencement of infertility and hormone deficiency treatment, together with counselling in an integrated management plan should improve both the short and long-term health of those with POF.

Mutations along the pituitary-gonadal axis affecting sexual maturation: novel information from transgenic and knockout mice

During the last 10 years, numerous activating and inactivating mutations have been detected in the genes encoding the two gonadotrophins, luteinising hormone (LH) and follicle-stimulating hormone (FSH), as well as their cognate receptors (R), LHR and FSHR. Because activation of the hypothalamic-pituitary-gonadal axis is a crucial event in the onset and progression of puberty, mutations affecting gonadotrophin action have major influence on this developmental process. Many of the phenotypic effects observed have been expected on the basis of the existing information about gonadotrophin action (e.g. delayed puberty), but also many unexpected findings have been made, including the lack of phenotype in women with activating LHR mutations, and the discrepancy in phenotypes of men with inactivating mutations of FSHbeta (azoospermia and infertility) and FSHR (oligozoospermia and subfertility). Some of the possible mutations, such as inactivating LHbeta and activating FSHR mutations in women, have not yet been detected. Genetically modified mice provide relevant phenocopies for the human mutations and serve as good models for studies on molecular pathogenesis of these conditions. They may also predict phenotypes of the mutations that have not yet been detected in humans. We review here briefly the effects of gonadotrophin subunit and receptor mutations on puberty in humans and contrast the information with findings on genetically modified mice with similar mutations.

Polycystic ovary syndrome: etiology and pathogenesis

OBJECTIVE

To provide a review of the pathogenesis of polycystic ovary syndrome.

DESIGN

Literature survey.

RESULT(S)

Three major pathophysiologic hypotheses have been proposed to explain the clinical findings of polycystic ovary syndrome (PCOS) related to three major laboratory findings: the LH hypothesis, the insulin hypothesis and the ovarian hypothesis. Although the presence of many small follicles with a high androgen to estrogen ratio was first thought to represent a high rate of follicular atresia in polycystic ovaries, recent studies have demonstrated that the granulosa cells are viable and able to respond to FSH stimulation with normal increases in estradiol production. Thus, a new hypothesis has arisen that FSH activity is somehow blocked at the ovarian level.

CONCLUSION(S)

PCOS is a syndrome involving defects in primary cellular control mechanisms that result in the expression of chronic anovulation and hyperandrogenism. In this syndrome, the relation between the various parameters is of particular interest. These relations constitute the cornerstone of the pathogenesis of PCOS. The fact that the pathogenesis of PCOS has not yet been clarified, despite the plethora of relative information, may be the result of a general way of thinking in the interpretation of several scientific data, and especially those that refer to biochemical phenomena. The use of the various models of the theory of chaos, that permits a concrete approach for the interpretation of data, may constitute an optional procedure for the future understanding of the association of different parameters and their disturbances in the pathogenesis of the polycystic ovary syndrome.

GRIS: glycoprotein-hormone receptor information system

The glycoprotein-hormone receptor information system (GRIS) presents a comprehensive view on all available molecular data for the lutropin/choriogonadotropin receptor, follitropin receptor, and thyrotropin receptor G protein-coupled receptors. It features a mutation database presently containing 696 point mutations, combined with all sequences and the associated homology models. The mutation information was automatically extracted from the literature and manually augmented with respect to constitutivity, surface expression, sensitivity to hormones, and binding affinity. All information in this integrated system is presented in a G protein-coupled receptor specialist-friendly way. A series of interactive tools such as rotamer analysis, mutation prediction, or cavity visualization aids with the design and interpretation of experiments. A universal residue numbering system has been introduced to ease database searches as well as the use of the information in conjunction with literature data from diverse origins. Users can upload new mutations. GRIS is freely accessible at http://gris.ulb.ac.be/.

Regulation of baboon fetal ovarian folliculogenesis by estrogen

Although it is well established that formation of the pool of follicles available for ovarian function and fertility in adulthood in human and non human primates occurs in utero, our understanding of the regulation of fetal ovarian development is incomplete. Our laboratories have been instrumental in establishing the baboon as a model for the study of human reproductive endocrinology and showed that estrogen plays a central integrative role in regulating fetal-placental development. Therefore, we adapted our baboon model to study the role of estrogen on fetal ovarian development. Estrogen receptors alpha and beta were expressed in pregranulosa cells and interfollicular nests of the baboon fetal ovary. In baboons in which estrogen levels had been suppressed by administration of an aromatase inhibitor throughout the second half of gestation, fetal ovarian follicle numbers were reduced by 50%, whereas the number of interfollicular nests comprised of oocytes and pregranulosa cells was increased. The decrease in follicles in estrogen-deprived animals was associated with a marked upregulation of expression of alpha-inhibin, but not activins or activin receptors and signaling molecules. Moreover, the majority of the follicles formed in ovaries of estrogen-depleted fetuses appeared unhealthy and contained oocytes with a marked reduction/depletion in microvilli, structures essential for uptake of substrates from surrounding granulosa cells. We propose that estrogen regulates fetal ovarian folliculogenesis and formation of healthy oocytes by controlling the intraovarian activin:inhibin ratio and the development of oocyte microvilli. These findings demonstrate a need for translational research studies of the impact of impairment of estrogen action/availability on reproductive function in adulthood.

Meat and Livestock Association Plenary Lecture 2005. Oocyte signalling molecules and their effects on reproduction in ruminants

Sheep (Ovis aries) are a highly diverse species, with more than 900 different breeds that vary significantly in their physiological characteristics, including ovulation rate and fecundity. From examination of inherited patterns of ovulation rate, several breeds have been identified with point mutations in two growth factor genes that are expressed in oocytes. Currently, five different point mutations have been identified in the BMP15 (GDF9b) gene and one in GDF9. Animals heterozygous for the GDF9 and/or the BMP15 mutations have higher ovulation rates than their wild-type counterparts. In contrast, those homozygous for any of the aforementioned BMP15 or GDF9 mutations are sterile owing to arrested follicular development. In bovine and ovine ovaries, GDF9 was expressed exclusively in oocytes throughout follicular growth from the primordial stage of development, whereas in sheep BMP15 was expressed exclusively in oocytes from the primary stage: no data for the ontogeny of BMP15 expression are currently available for cattle. In vitro, ovine growth differentiation factor 9 (oGDF9) has no effect on 3H-thymidine incorporation by either bovine or ovine granulosa cells, whereas ovine bone morphogenetic protein 15 (oBMP15) has modest (1.2- to 1.6-fold; P < 0.05) stimulatory effects. Ovine GDF9 or oBMP15 alone inhibited progesterone production by bovine granulosa cells, whereas in ovine cells only oGDF9 was inhibitory. The effects of oGDF9 and oBMP15 together were often cooperative and not always the same as those observed for each factor alone. Active immunisation of ewes with BMP15 and/or GDF9 peptides affected ovarian follicular development and ovulation rate. Depending on the GDF9 and/or BMP15 vaccine formulation, ovulation rate was either increased or suppressed. A primary and single booster immunisation of ewes with a BMP15 peptide in a water-based adjuvant has led to 19–40% increases in lambs born per ewe lambing. Collectively, the evidence suggests that oocyte signalling molecules have profound effects on reproduction in mammals, including rodents, humans and ruminants. Moreover, in vivo manipulation of these oocyte signalling molecules provides new opportunities for the management of the fertility of ruminants.

What have we learned about gonadotropin function from gonadotropin subunit and receptor knockout mice?

A number of biochemical and physiological studies elucidated the roles of pituitary and placental glycoprotein hormones. Advances in the past two decades in manipulating the mouse genome by random or site-specific mutagenesis have heralded a new dimension to our understanding of the biology of gonadotropins. It is now possible to model many human reproductive disorders involving gonadotropins/gonadotropin-signaling in the mouse. Mutant mice selectively lacking either FSH or LH or their cognate receptors have been generated. The gonadotropin ligand and the corresponding receptor knockout mice mostly phenocopy each other. Analyses with these genetic models confirmed earlier physiological studies; in addition they also revealed novel roles for gonadotropins previously unrecognized. While FSH action seems dispensable for male but not female fertility, absence of LH causes infertility in both the sexes. While Sertoli cell number and germ cell carrying capacity of the Sertoli cells in compromised in FSH mutants, both somatic and germ cell lineages are affected in the LH mutants resulting in complete male infertility. FSH mutant females demonstrate a preantral stage block in folliculogenesis and FSH alone is not sufficient to promote full folliculogenesis in the absence of LH. Pre-ovulatory stage follicles do not form and most of the follicles undergo apoptosis in the absence of LH. Many extra-gonadal phenotypes have been described for the receptor knockout mice and whether these bear any resemblances to those in patients with similar inactivating mutations in the receptors for FSH and LH remains an open question. Thus the in vivo models will continue to have a significant impact in understanding gonadotropin physiology and pathophysiology and serve as novel genetic tools to study signaling mechanisms in the gonads.

An update of the pathophysiology of human gonadotrophin subunit and receptor gene mutations and polymorphisms

New information about mutations and polymorphisms in the genes for the gonadotrophins and their receptors has become available in the last few years. In this short review mutations and polymorphisms in gonadotrophins, their receptors and their pathophysiological effects and implications are discussed. An increasingly clear picture about the structure–function relationships of gonadotrophin action is emerging from the combining the types and the locations of the mutations with their phenotypic effects and the information about the crystal structure of these molecules.

Human FSH beta subunit gene is highly conserved

FSH is a pituitary gonadotropin that along with LH plays a key role in the regulation of gonadal function. The gonadotropic hormones are composed of two subunits, the common alpha subunit and the hormone-specific beta subunit, which determines the binding to specific receptors and induction of biological response. Unlike the LHbeta gene, shown in earlier studies to harbour several amino acid-altering polymorphisms and mutations, information about the eventual sequence variation of the human FSHbeta subunit is not available. In this study, we made sequence analysis and comparison of polymorphisms found in FSHbeta in two Caucasian populations, the Finns and the Danes. It was found that FSHbeta subunit is highly conserved in these populations. Compared with the published sequences, only three silent polymorphisms were detected in the coding regions of the gene, and the promoter sequence was completely identical with the reported sequence. Two of the polymorphisms found were novel, one in the Finnish and one in the Danish population. The results of the sequence analysis show that the human FSHbeta gene is highly conserved and amino acid changing mutations are apparently extremely rare, at least in the samples collected randomly from control populations. This may be due to the crucial role of normal FSH function in the regulation of fertility.

Clinical pharmacology of gonadotrophin preparations

The practice of ovulation induction and superovulation for IVF has progressed in many ways since the first reports of pregnancies after IVF over 25 years ago. The pharmacology of gonadotrophins has advanced alongside other developments, leading to safer, easier and more effective treatments for anovular infertility and IVF ovulation induction. This review uses current concepts of the basic physiology of gonadotrophin actions during the natural ovarian cycle as a starting point from which to assess their uses in anovulation and assisted reproduction. The relative merits of urinary and recombinant gonadotrophins are discussed, along with their uses in combination with gonadotrophin-releasing hormone agonists and antagonists.

Premature ovarian failure

Premature ovarian failure (POF) causing hypergonadotrophic hypogonadism occurs in 1% of women. In majority of cases the underlying cause is not identified. The known causes include: (a) Genetic aberrations, which could involve the X chromosome or autosomes. A large number of genes have been screened as candidates for causing POF; however, few clear causal mutations have been identified. (b) Autoimmune ovarian damage, as suggested by the observed association of POF with other autoimmune disorders. Anti-ovarian antibodies are reported in POF by several studies, but their specificity and pathogenic role are questionable. (c) Iatrogenic following surgical, radiotherapeutic or chemotherapeutic interventions as in malignancies. (d) Environmental factors like viral infections and toxins for whom no clear mechanism is known. The diagnosis is based on finding of amenorrhoea before age 40 associated with FSH levels in the menopausal range. Screening for associated autoimmune disorders and karyotyping, particularly in early onset disease, constitute part of the diagnostic work-up. There is no role of ovarian biopsy or ultrasound in making the diagnosis. Management essentially involves hormone replacement and infertility treatment, the only proven means for the latter being assisted conception with donated oocytes. Embryo cryopreservation, ovarian tissue cryopreservation and oocyte cryopreservation hold promise in cases where ovarian failure is foreseeable as in women undergoing cancer treatments.

Gonadotropin gene targeting and biological implications

Pituitary gonadotropins FSH and LH are heterodimeric glycoproteins consisting of a common alpha and a hormone-specific beta subunit that are non-covalently linked. These hormones orchestrate gonadal growth, differentiation, and function by regulating both steroid-ogenesis and gametogenesis. Advances in the past two decades in manipulating the mouse genome by site-specific mutagenesis have heralded a new dimension to our understanding of the biology of gonadotropins. Using these gene-targeting approaches, knockout mice lacking the hormone-specific gonadotropin subunits, and hence the functional dimeric hormones, have been generated. These individual gonadotropin-deficient mice are useful to delineate the distinct in vivo biological roles of FSH and LH. These mice also serve as valuable genetic tools to study the signaling mechanisms within the gonads and help a better understanding of some forms of human infertility.

Clinical and hormonal features of selective follicle-stimulating hormone (FSH) deficiency due to FSH beta-subunit gene mutations in both sexes

OBJECTIVE

To report the clinical, hormonal, and molecular features of a female adolescent with selective FSH deficiency. In addition, a complete review of previous cases is provided, focusing on hormonal aspects.

DESIGN

Clinical study.

SETTING

University hospital.

PATIENT(S)

A 16-year-old girl with primary amenorrhea and poor breast development due to isolated FSH deficiency.

INTERVENTION(S)

Blood drawing before and after GnRH stimulation and pelvic ultrasound examination.

MAIN OUTCOME MEASURE(S)

Gonadotropin and E(2) measurements and sequencing of the FSH beta-subunit gene.

RESULT(S)

The patient was referred for primary amenorrhea and partial breast development (Tanner III). Her basal and GnRH-stimulated LH levels were elevated (31 IU/L and 98 IU/L, respectively), whereas her FSH levels were undetectable (<1 IU/L) in both conditions. Estradiol levels were low (<13 pg/mL). Automatic sequencing showed a nucleotide substitution of C for A in exon 3, resulting in a homozygous nonsense mutation in amino acid position 76 (Tyr76X) of the FSH beta-subunit.

CONCLUSION(S)

The Tyr76X mutation of the FSH beta-subunit was associated with a partial phenotype of FSH deficiency. To date, only four loss-of-function mutations of the FSH beta-subunit have been described in eight patients with undetectable serum FSH and high serum LH levels. Therefore, this unusual hormonal profile strongly suggests a defect in the FSH beta-subunit in both sexes.

PCOS: an ovarian disorder that leads to dysregulation in the hypothalamic–pituitary–adrenal axis?

This review focuses on the role of the ovaries in the pathogenesis of the polycystic ovarian syndrome. In particular, the failure of follicular development, hypothalamo-pituitary dysregulation, alterations in adrenal steroid output and derangement of intermediary metabolism are discussed in the context of the ovaries. It is concluded that the central and adrenal alterations associated with PCOS are unlikely to be primary but rather are secondary to the events within the ovary.

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

A 30-year-old man who presented with delayed puberty and infertility was found to have hypogonadism associated with an absence of circulating luteinizing hormone. The patient had a homozygous missense mutation in the gene that encodes the beta subunit of luteinizing hormone (Gly36Asp), a mutation that disrupted a vital cystine knot motif and abrogated the heterodimerization and secretion of luteinizing hormone. Treatment with human chorionic gonadotropin increased circulating testosterone, promoted virilization, and was associated with the appearance of normal spermatozoa in low concentrations. This case illustrates the important physiological role that luteinizing hormone plays in male sexual maturation and fertility.

Novel expression of gonadotropin subunit genes in oocytes of the gilthead seabream (Sparus aurata)

It is widely believed that FSH and LH, which are known to play key roles in controlling the production of functional oocytes in vertebrates, are synthesized and secreted exclusively by the anterior pituitary. Here we present evidence for the novel expression of FSHbeta, LHbeta, and the common glycoprotein-alpha (Cgalpha) in the gilthead seabream ovary. Using in situ hybridization and immunocytochemistry, FSHbeta was detected in primary-growth and secondary-growth-I oocytes, LHbeta was found in secondary-growth oocytes, and Cgalpha was observed in both primary and secondary-growth oocytes. Northern blot analyses demonstrated that Fshbeta transcript is 0.6 kb in both pituitary and ovary, whereas the ovarian Lhbeta transcript (1.1 kb), unexpectedly, is longer than the known pituitary Lhbeta transcript (0.6 kb). Sequence analyses revealed that ovarian Lhbeta is driven by a different promoter than pituitary Lhbeta, which generates an additional 459 bases at the distal portion of the 5'-untranslated region of the ovarian Lhbeta. Furthermore, using in vitro ovarian fragment incubation, we demonstrated that mammalian GnRH analog agonist enhanced the expression of ovarian Fshbeta (up to 2.7-fold), Lhbeta (up to 1.4-fold), Cgalpha (up to 1.8-fold), and the secretion of ovarian LH (up to 2.2-fold). In contrast, GnRH antagonist, analog E, suppressed the secretion of ovarian LH. Our findings suggest that a GnRH-gonadotropin axis is present in the gilthead seabream ovary and that FSH and LH, the well-characterized pituitary hormones, may have prominent novel roles in teleost intraovarian communication between oocytes and ovarian follicle cells.

Mutations affecting gonadotropin secretion and action

A number of mutations are known to disturb the development and function of the hypothalamic-pituitary-gonadal axis. They affect hypothalamic-pituitary-gonadal function at multiple levels, from the migration of gonadotropin releasing hormone neurons to the hypothalamus right through to gonadotropin action in the ovary and testis. Most of the mutations are inactivating, causing various forms of hypogonadism. Exceptions are the activating mutations of the luteinizing hormone receptor, causing male-limited gonadotropin-independent precocious puberty. The human mutations and genetically modified animal models have clarified the molecular pathogenesis of hypogonadism and such disorders can now be diagnosed using molecular biological techniques, enabling selection of specific treatments and appropriate counselling of patients and their families.

Significance of ovarian histology in the management of patients presenting a premature ovarian failure

BACKGROUND

Premature ovarian failure (POF) is a heterogeneous syndrome, possibly due to mutations of genes involved in the normal development of the ovary and/or follicles. Based essentially on animal models, these mutations are associated with various ovarian phenotypes, from a complete absence of follicles to a partial follicular maturation. The aim of the present study was to determine whether ovarian histology, compared to pelvic ultrasonography, would be helpful in identifying which patients display an impaired follicular reserve and/or growth, and in orientating the search for POF aetiology.

METHODS AND RESULTS

We studied a cohort of 61 patients suffering from POF with a normal karyotype. Their median age (range) at diagnosis was 26 years (15-39). The FSH plasma level was high, 67.0 IU/l (13-155). Estradiol and inhibin B plasma levels were low: 18.5 pmol/l (18.5-555) and 5 pg/ml (5-105) respectively. Both pelvic ultrasonography and ovarian biopsies were performed in each patient. The presence of follicles suggested at ultrasonography was confirmed at histology in 56% of the patients. Ovarian histology led to the distinction of two phenotypes: (i) small-sized ovaries, deprived of follicles; and (ii) normal-sized ovaries with partial follicular maturation. To confirm the value of ovarian biopsies, samples from 20 normal women were studied. These demonstrated that ovarian biopsy at random enables reliable assessment of follicular presence, especially when their size is <2 mm.

CONCLUSION

Ovarian histology appears to be a reliable tool in evaluating the follicular reserve, and helpful and complementary to clinical and hormonal phenotyping in orienting the search for the various genetic causes of POF syndrome.

Absence of the genetic variant Val79Met in human chorionic gonadotropin-beta gene 5 in five European populations

Chorionic gonadotropin (CG) is an essential signal in establishment and maintenance of pregnancy in humans and higher primates. A G-to-A transition in exon 3 of human CGbeta gene 5, changing the naturally occurring valine residue to methionine in codon 79 (Val(79)Met) has been reported at carrier frequency 4.2% in a random population from the Midwest of the United States. The biological activity of the variant hCG was similar to that of wild-type (WT) hCG. However, the Val(79)Met beta-subunit displayed impaired ability to assemble with alpha-subunit, and the amount of hCG alpha/beta heterodimers formed and secreted by transfected cells was seriously impaired in the previous study. Because of these functional implications we found it important to study the occurrence of the Val(79)Met hCGbeta variant in other populations. By using a PCR-RFLP method, a search for the Val(79)Met hCGbeta variant was carried out on a total of 580 DNA samples from five European populations (Finland, Denmark, Greece, Germany and the UK). The results demonstrated an absence of the polymorphism in these populations. Hence, the naturally occurring variant (Val(79)Met) of the hCGbeta gene 5, found previously at high frequency in the US, is clearly less common, or absent, in the European populations studied.

Identification of Substituted 6-Amino-4-phenyltetrahydroquinoline Derivatives: Potent Antagonists for the Follicle-Stimulating Hormone Receptor

Substituted 6-amino-4-phenyl-tetrahydroquinoline derivatives are described that are antagonists for the G(s)-protein-coupled human follicle-stimulating hormone (FSH) receptor. These compounds show high antagonistic efficacy in vitro using a CHO cell line expressing the human FSH receptor. Antagonist 10 also showed a submicromolar IC(50) in a more physiologically relevant rat granulosa cell assay and was found to significantly inhibit follicle growth and ovulation in an ex vivo mouse model. This compound class may open the way toward a novel, nonsteroidal approach for contraception.

Polycystic Ovary Syndrome

Women with polycystic ovarian syndrome have chronic anovulation and androgen excess not attributable to another cause. This condition occurs in approximately 4% of women. The fundamental pathophysiologic defect is unknown, but important characteristics include insulin resistance, hyperandrogenism, and altered gonadotropin dynamics. Inadequate follicle-stimulating hormone is hypothesized to be a proximate cause of anovulation. Obesity frequently complicates polycystic ovarian syndrome but is not a defining characteristic. The diagnostic approach should be based largely on history and physical examination, thus avoiding numerous laboratory tests that don't contribute to clinical management. Women with polycystic ovarian syndrome typically present because of irregular bleeding, hirsutism, and/or infertility. These conditions can be treated directly with oral contraceptives, oral contraceptives plus spironolactone, and ovulation induction, respectively. However, women with polycystic ovarian syndrome also have a substantially higher prevalence of diabetes and increased risk factors for cardiovascular disease. They should also be screened, therefore, for these conditions and followed closely if any risk factors are uncovered. For obese women with polycystic ovarian syndrome, behavioral weight management is a central component of the overall treatment strategy.

Molecular abnormalities of FSH and LH action

The identification of naturally occurring genetic mutations in individuals with disorders of reproductive function is the first logical step to therapy. To date, diagnostic investigations have been assisted by polymerase chain reaction and the development of an increasing number of effective screening techniques to scan genomic DNA (deoxyribonucleic acid) for causative mutations. The continued expansion of these technologies, coupled with high throughput gene sequencing, will ultimately result in automated DNA diagnosis for the practicing clinician at the point of care. At that time, the direct examination of a patient's DNA will be the definitive means of establishing the presence of specific genetic changes that cause or increase one's susceptibility to disease. This presentation selects important candidate genes in the human hypothalamic-pituitary-ovarian axis (HPG), reviews our knowledge of the spontaneously occurring human mutations that affect these genes, and reviews the biological implications of this information. To date, causative mutations in candidate genes have provided important insights into the transcription factors, receptors, and hormones that regulate the HPG axis at many levels. A major challenge in this field is that mutations in many of these genes and others remaining to be identified lead to infertility. The reduction in reproductive fitness due to these mutations limits the ability of investigators to use traditional genetic linkage and association studies to identify and clone important unidentified reproductive genes. Fortunately analysis of human gametes and new strategies that are being developed for the identification and mapping of complex human diseases will become increasingly important in continuing studies of idiopathic human infertility. At this time, it is helpful for the reader to become acquainted with some of the prototype mutations in candidate genes, their phenotypic consequences, and their prevalence. This presentation is designed to describe the known mutations in the gonadotropin genes and the genes encoding their respective receptors. The phenotypic effects of these mutations is compared, and evidence for causation is reviewed.

Genetic causes of human infertility

The currently characterized chromosomal disorders and gene mutations that cause infertility in humans were reviewed. Of the four arbitrary compartments, genes expressed in the gonad comprise the most common site affected by mutations causing infertility. Clinicians should be aware of the most common causes that have clinical implications: (1) women with a 45,X cell line commonly have cardiac anomalies that may pose a risk for maternal death in pregnancies achieved by donor egg IVF; (2) men with Y-chromosome deletions may produce male offspring with the same deletion, rendering them infertile; (3) CBAVD must be ascertained in men with azoospermia because of the risk for having a child with CF; and (4) some women with premature ovarian failure may be fragile X syndrome carriers, so other family members may be at risk for the full syndrome. In the future, more genes will be identified to cause infertility in humans, which will translate into clinical significance. In select cases, in which the genetic defect is known, it may be possible to use preimplantation genetic diagnosis to screen embryos prior to uterine transfer.

Molecular basis of pubertal abnormalities

The causes of abnormal pubertal development are numerous. Recent molecular investigation has increased our understanding of the genetic basis of pubertal disorders. Investigators have identified some of the genes that are critical for normal puberty and have begun to elucidate the genes and pathogenesis of genetic disorders associated with abnormal pubertal development. Identification of specific chromosomal abnormalities and gene mutations allows for diagnostic testing and enables the clinician to provide accurate counseling of the recurrence risk for relatives. In the future, knowledge of the genetic basis of these disorders will facilitate the development of novel therapies and approaches to the fertility assessment and treatment of individuals with pubertal disorders. Although great strides have been made in identifying these genes, questions remain. Why do some genetic mutations affect puberty differentially in males and females? What is the long-term impact in terms of future fertility, and what is the risk to the offspring of such patients? Further research is needed to address these issues and to identify additional genetic loci involved in pubertal development.

[Genetic origin of spermatogenesis impairments: clinical aspects and relationships with mouse models of infertility]

Human spermatogenesis failures appear frequently as idiopathic and may be due to genetic causes. Mutations of genes involved in the hypothalamic/pituitary control of spermatogenesis have been described and account for several types of hypogonadotropic hypogonadism. Chromosomal abnormalities found in infertile patients are either gonosomal aneuploidies or structural anomalies which interfere with the normal chromosome behaviour at meiosis and lead to germ cell breakdown. Microdeletions of the Y chromosome are often undetectable at karyotype and are responsible for the loss of genes which compose the AZF factor. The increase in the number of mouse models of infertility will allow the description of many human genes involved in the spermatogenesis process provided that a detailed analysis of their genotype-phenotype relationships is performed.

Developmental regulation of follicle-stimulating hormone receptor messenger RNA expression in the baboon fetal ovary

In the adult ovary, pituitary FSH via interaction with its receptor (FSHR) is required for follicular maturation and granulosa cell development. In humans and nonhuman primates, the pool of follicles available for adult ovarian function is established in utero. However, our understanding of the ontogeny and developmental regulation of FSHR in the ovary of the primate fetus is incomplete. Our goal was to determine whether the baboon fetal ovary expresses the full-length FSHR mRNA transcript and whether levels are developmentally regulated. Fetal ovaries were obtained at mid (Day 100) and late (Day 165) gestation (term = Day 184) from untreated baboons and on Day 165 from baboons in which fetal estrogen levels were either decreased by >95% by treatment with the aromatase inhibitor CGS 20267 or restored to 30% of normal by treatment with CGS 20267 plus estradiol benzoate administered s.c. to the mother on Days 100-164. The full-length 2088-base pair FSHR mRNA transcript was expressed in ovaries of adult and fetal baboons untreated or treated with CGS 20267 or CGS 20267 and estrogen. Mean (+/-SEM) FSHR mRNA levels (ratio of FSHR mRNA:18S rRNA), quantified by reverse transcription polymerase chain reaction, were increased (P < 0.05) 2-fold between mid (0.34 +/- 0.06) and late gestation (0.76 +/- 0.07), an increase prevented (P < 0.05) in estrogen-depleted baboons (0.44 +/- 0.10) and partially restored by treatment with CGS 20267 and estrogen (0.58 +/- 0.16). We previously showed that the number of follicles/0.33 mm2 in fetal ovaries of untreated baboons in late gestation was reduced 50% by treatment with CGS 20267 and restored to normal in baboons treated with CGS 20267 and estrogen. Thus, when corrected for the number of follicles/0.33 mm2, FSHR mRNA levels were similar in baboon fetal ovaries untreated (0.010 +/- 0.001) or treated with CGS 20267 (0.009 +/- 0.002) or CGS 20267 and estrogen (0.007 +/- 0.003). We conclude that estrogen plays a major role in regulating ovarian FSHR mRNA expression in the primate fetus, and that the developmental increase in FSHR mRNA levels reflects the estrogen-dependent increase in folliculogenesis (i.e., increased number of granulosa cells and oocytes).

Analysis of the Cys82Arg mutation in follicle-stimulating hormone beta (FSHbeta) using a novel FSH expression vector

OBJECTIVE

To determine the effect of the Cys82Arg FSHbeta mutation from a patient with isolated FSH deficiency upon follicle-stimulating hormone (FSH) levels in vitro.

DESIGN

In vitro analysis of the Cys82Arg mutation and comparison with the phenotype.

SETTING

Tertiary medical center setting.

PATIENT(S)

DNA sequence of the FSHbeta gene and clinical description from a patient with isolated FSH deficiency.

INTERVENTION(S)

Construction of a new vector containing the cDNAs for the alpha-subunit and beta-subunit of FSH (palphaFSHbeta) followed by mutagenesis and transfection into Chinese hamster ovary cells.

MAIN OUTCOME MEASURE(S)

Immunoreactive and bioactive FSH levels from the CHO cellular media.

RESULT(S)

Although expression of both subunits was present, both immunoreactive and bioactive FSH levels were unmeasurable from cellular media containing the mutation versus wild type.

CONCLUSION(S)

The Cys82Arg mutation in a male with normal puberty and azoospermia results in profound deficiency of FSH in vitro, thereby confirming the molecular basis of hypogonadism in this patient and documenting the importance of the Cys residue at position 82 of the FSHbeta subunit.

Isolated follicle-stimulating hormone (FSH) deficiency in a young man with normal virilization who did not have mutations in the FSHbeta gene

OBJECTIVE

To determine the cause of isolated FSH deficiency in a young infertile man.

DESIGN

Case report.

SETTING

Clinical and genetic studies in an academic research environment.

PATIENT(S)

A 19-year-old man with normal virilization, azoospermia, and isolated FSH deficiency.

INTERVENTION(S)

Pituitary and gonadal functions were evaluated at baseline and after repeated GnRH stimulation. FSH was tested with both immunological and biological methods. The FSHbeta gene was sequenced in the patient and in a series of 50 controls.

MAIN OUTCOME MEASURE(S)

Clinical, endocrine, and genetic characterization of an infertile patient with isolated FSH deficiency.

RESULT(S)

LH and T secretions were normal. No interference in FSH measurement was detected, and serum FSH concentrations were very low and completely unresponsive to repeated GnRH stimulation. No circulating FSH-like bioactivity was detected by means of rat Sertoli cell bioassay. Other pituitary functions were unaffected, and no lesions were seen at pituitary nuclear magnetic resonance (NMR). Inhibin B and activin levels were normal, but a progressive decrease of activin concentrations was seen during GnRH stimulation. The coding sequence of the FSHbeta gene was normal, but the patient was homozygous for a novel G/T substitution in the promoter region within a P response element. This substitution was present in heterozygosity in eight out of 50 controls and in homozygosity in one man with normal FSH levels.

CONCLUSION(S)

We report an infertile male with isolated FSH deficiency but no evidence of mutations in the FSHbeta gene. The G/T substitution in the FSHbeta promoter represents a novel silent polymorphism, indicating that other defects in factors involved in FSH-specific expression should be taken into account.

Current and future genetic screening for male infertility

Although much of male infertility is currently unexplained, it is likely that underlying defects in critical genes or entire gene pathways are responsible. Because powerful technologies exist to bypass severe male-factor infertility, improving the diagnosis of genetic infertility is important for the infertile couple, not only to explain the problem but also to inform them of conditions potentially transmissible to offspring.

Understanding new genetics of male infertility

PURPOSE

Greater than 10% of couples are unable to achieve pregnancy. In at least 30% to 50% of these infertility cases a male factor abnormality is involved. Genetic defects are believed to be the cause of a significant percent of these abnormalities. In fact, defects causing infertility, such as chromosomal disorders and congenital hypothalamic-pituitary-gonadal axis syndromes, have long been recognized. With the development of gene targeting technologies in animal models many genes required for male fertility in animals are known, contributing to our understanding of the etiology of this important health problem. We present not only recognized genetic disorders associated with male infertility, but also its emerging and previously unrecognized genetic etiologies.

MATERIALS AND METHODS

This review is organized to enable the reader to recognize promptly the major types of genetic defects associated with male infertility, their clinical characteristics and appropriate therapeutic approaches. Due to the explosion of current knowledge in this field and to length restrictions the discussion of genetic defects is concise, referencing predominantly review articles relevant to the topic.

RESULTS

Assisted reproductive technologies for overcoming sterility resulting from unrecognized etiologies may have important potential consequences for infertile couples and their offspring.

CONCLUSIONS

Familiarity with the genes associated with male infertility is essential for the urologist to better understand, diagnose and treat the male factor couple.

Identification and characterization of a selective, nonpeptide follicle-stimulating hormone receptor antagonist

The glycoprotein hormones (LH, FSH, and TSH) are critical to the maintenance of physiological homeostasis and control of reproduction. However, despite an obvious utility for synthetic pharmacological agents, there are few reports of selective, nonpeptide agonists or antagonists to receptors for these hormones. We have identified and characterized a novel synthetic molecule capable of inhibiting the action of FSH. This compound, 7-[4-[Bis-(2-carbamoyl-ethyl)-amino]-6-chloro-(1,3,5)-triazin-2-ylamino)-4-hydroxy-3-(4-methoxy-phenylazo)-naphthalene]-2-sulfonic acid, sodium salt (compound 1), is a selective, noncompetitive inhibitor of the human (h) and rat (r) FSH receptors (FSHRs). Compound 1 selectively inhibited binding of [(125)I]hFSH with an IC(50) value of 5.4 +/- 2.3 micro M. Radioligand-binding assays were performed using the baculovirus expressed extracellular domain of hFSHR (BV-tFSHR) to demonstrate site-specific interaction. Compound 1 competed for [(125)I]hFSH binding to BV-tFSHR with an IC(50) value of 10 +/- 2.8 micro M. Functionally, compound 1 inhibited hFSH-induced cAMP accumulation and steroidogenesis in vitro with an IC(50) value of 3 +/- 0.6 micro M. Competition of compound 1 for binding to other glycoprotein hormone receptors and other G protein-coupled receptors demonstrated select activity for FHSRs. Compound 1 inhibited ovulation in immature and cycling adult rats. These data provide proof of concept that selective, small molecule antagonists can be designed for glycoprotein hormone receptors.

FSH beta gene mutations in a female with partial breast development and a male sibling with normal puberty and azoospermia

FSH is a dimeric pituitary glycoprotein hormone that regulates gonadal function. Human mutations in the FSH beta gene have been shown to produce complete deficiency states in which pubertal development and reproductive capacity are inhibited. To date, no patients with partial or complete pubertal development due to FSH beta mutations have been documented in humans. We describe and characterize affected siblings, a male and a female, with evidence of pubertal development due to homozygosity for a Tyr76X nonsense mutation in the FSH beta gene. In vitro analysis of this mutant demonstrates unmeasurable FSH by immunoassay and by two different bioassays, using either cAMP (homologous FSH bioassay) or estradiol (rat granulosa cell assay) as the endpoints. In additional in vitro analyses, mutants previously found in patients with a phenotype of complete FSH deficiency (Cys51Gly and Val61X) and the Tyr76X were compared in the same immuno- and bioassays. All mutations failed to produce measurable FSH by all assays. Unexpectedly, these siblings with isolated FSH deficiency due to a nonsense FSH beta mutation had some evidence of puberty, suggesting that other factors might preserve gonadal steroidogenesis in the absence of FSH or that current bioassays cannot discriminate among very low FSH levels.

Genetics and hypogonadotrophic hypogonadism

Hypothalamic pulsatile gonadotrophin-releasing hormone secretion, stimulating pituitary gonadotrophin secretion, is essential for adult reproductive function. This neuroendocrine drive to the reproductive axis is critically dependent on a sequence of developmental events in utero. During early foetal life, gonadotrophin-releasing hormone neurones migrate from the nasal placode to the medial basal hypothalamus where gonadotrophin-releasing hormone can be transported down portal vessels to the anterior pituitary. Gonadotrophin-releasing hormone secretion is active fleetingly neonatally but soon becomes quiescent throughout childhood. At the time of puberty activation of gonadotrophin-releasing hormone secretion reawakens the hypothalamic pituitary-gonadal axis and secondary sexual maturation is triggered. Any disruption in gonadotrophin-releasing hormone secretion will result in hypogonadotrophic hypogonadism. The clinical manifestations of this become apparent with secondary sexual maturation. Genetic mutations have been identified in a minority of cases. These include Kallmann syndrome, adrenal hypoplasia congenital, gonadotropin-releasing hormone receptor and luteinizing hormone or follicle-stimulating hormone beta-subunit gene mutations. The importance of these discoveries is important not only in relation to the conditions that result, but also for our better understanding of normal reproductive function.

Molecular, structural, and cellular biology of follitropin and follitropin receptor

Follitropin and the follitropin receptor are essential for normal gamete development in males and females. This review discusses the molecular genetics and structural and cellular biology of the follitropin/follitropin receptor system. Emphasis is placed on the human molecules when possible. The structure and regulation of the genes for the follitropin beta subunit and the follitropin receptor is discussed. Control of systemic and cellular protein levels is explained. The structural biology of each protein is described, including protein structure, motifs, and activity relationships. Finally, the follitropin/follitropin receptor signal transduction system is discussed.

The role of mutations affecting gonadotrophin secretion and action in disorders of pubertal development

A number of mutations that disturb the development and function of the hypothalamic-pituitary-gonadal (HPG) axis and cause disturbances in pubertal development are known today. These mutations have effects at all levels of the HPG axis, from the migration of gonadotrophin releasing hormone (GnRH) neurones from the nasal cavity to the hypothalamus, GnRH secretion, GnRH action, pituitary gonadotroph differentiation, gonadotrophin synthesis and secretion, right through to gonadotrophin action. Most of the mutations are inactivating, thus causing hypogonadism and arrest or delay of pubertal development. One exception is the activating mutations of the LH receptor, which causes the male-limited gonadotrophin-independent precocious puberty. The human mutations and animal models with disrupted function of orthologous genes have clarified the molecular pathogenesis of hypogonadism and disturbances of pubertal development. The correct diagnosis of these disorders using molecular biological techniques is now possible. This allows the selection of specific treatments and correct counselling of the patients and their families.

Human gene mutations causing infertility

The identification of gene mutations causing infertility in humans remains noticeably deficient at present. Although most males and females with infertility display normal pubertal development, nearly all of the gene mutations in humans have been characterised in people with deficient puberty and subsequent infertility. Gene mutations are arbitrarily categorised into four different compartments (I, hypothalamic; II, pituitary; III, gonadal; and IV, outflow tract). Diagnoses of infertility include hypogonadotrophic hypogonadism (compartments I and II), hypergonadotrophic hypogonadism (III), and obstructive disorders (compartment IV). Most gene mutations identified to date affect gonadal function, but it is also apparent that a large number of important genes in normal fertility have yet to be realised.

An immunoreactive peptide of the FSH involved in autoimmune infertility

The purpose of this study was to identify autoantigens contained in human ovary extracts. Serum samples from 36 infertile women with anti-ovary antibodies as detected with an ELISA technique were tested in Western blot against human ovary extracts. A reactive protein with a molecular mass matching that of the FSH was detected in 34 cases. These serum samples also reacted strongly in Western blot and ELISA with purified FSH and, in immunofluorescence, with pituitary cells. Using the Pepscan approach, with overlapping peptides matching the amino acid sequence of the human FSH beta-chain, several immunoreactive regions were evidenced. The 78-93 amino acid sequence of the human FSH beta-chain appeared as one of the major epitopes. Synthetic peptides of this region were prepared and demonstrated to react with human serum samples from women with anti-ovary antibodies. These data demonstrate that FSH can be an autoantigen, recognized by autoantibodies associated with infertility.

Synergism between FSH and activin in the regulation of proliferating cell nuclear antigen (PCNA) and cyclin D2 expression in rat granulosa cells

Follicular development is associated with both proliferation and differentiation of granulosa cells under the control of FSH. We show that regulation of genes involved in cellular proliferation by FSH can be functionally separated from the regulation of genes involved in granulosa cell differentiation by synergistic actions of activin and T. Incubation of undifferentiated rat granulosa cells with FSH, forskolin, activin-A, or T alone did not influence either the expression of the proliferation-associated genes cyclin D2 and proliferating cell nuclear antigen or the differentiation-associated genes P450 aromatase, LH receptor, P450 cholesterol side-chain cleavage enzyme, and 3 beta-hydroxysteroid dehydrogenase. However, when granulosa cells were stimulated with either FSH or forskolin in the presence of activin-A, significant increases (P < 0.05) were observed for cyclin D2 and proliferating cell nuclear antigen at both the mRNA and protein levels as well as mRNAs for P450 aromatase, LH receptor, P450 cholesterol side-chain cleavage enzyme and 3 beta-hydroxysteroid dehydrogenase. Although T synergized with FSH to increase the expression of mRNAs for P450 aromatase, LH receptor, P450 cholesterol side-chain cleavage enzyme, and 3 beta-hydroxysteroid dehydrogenase, it did not interact with FSH to increase the expression of mRNAs for cyclin D2 and proliferating cell nuclear antigen. The differences in the actions of activin and T could provide a cellular mechanism by which FSH-regulated granulosa cell proliferation could be functionally separated from FSH-regulated granulosa cell differentiation.

Inherited disorders of the gonadotropin hormones

Pulsatile GnRH acts at the GnRH receptor on gonadotropes to stimulate gonadotropin gene expression, hormone synthesis and secretion. The pituitary gonadotropins, LH and FSH, stimulate steroid production and gametogenesis in males and in females. Gonadotropin production thus requires the normal development and function of hypothalamic GnRH-producing neurons and pituitary gonadotrope cells. Genes involved in gonadotrope development and/or gene expression include SF1, DAX1, KAL, GNRHR, PC1, HESX1, LHX3, PROP1, LH beta, and FSH beta. Given the complex control of gonadotropin biosynthesis and secretion, it is not surprising that genetic abnormalities have been identified at several of these steps. Some of the mutations that will be reviewed include: (1) SF1 and DAX1-orphan nuclear receptors that are expressed at multiple levels throughout the reproductive axis; (2) KAL-X-linked Kallmann syndrome, where there is abnormal development of hypothalamic GnRH-producing neurons; (3) PC1-causing abnormal processing of GnRH and GNRHR mutations that impair action at the GnRH receptor; (4) HESX1, LHX3, PROP1-abnormal development/function of the gonadotrope cell lineage; (5) LH beta and FSH beta-mutations in the gonadotropin genes that cause structural abnormalities in the hormones. Although all of these gene defects lead to gonadotropin deficiency, each disorder is associated with unique phenotypic or hormonal features. Characterization of the molecular basis of gonadotropin deficiency is useful for directing therapy and for genetic counseling. Identification of these mutations also provides insight into the pathways that govern reproduction.