Menstrual disorders and infertility caused by inactivating mutations of the luteinizing hormone receptor gene

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.

Ovarian macrocysts and gonadotrope-ovarian axis disruption in premenopausal women receiving mitotane for adrenocortical carcinoma or Cushing's disease

CONTEXT

Mitotane is an adrenolytic and anticortisolic drug used in adrenocortical carcinoma (ACC), Cushing's disease (CD), and ectopic ACTH syndrome. Its effects on the ovaries are unknown.

OBJECTIVE

To evaluate the ovarian and gonadotrope effects of mitotane therapy in premenopausal women.

PATIENTS

We studied 21 premenopausal women (ACC: n=13; CD: n=8; median age 33 years, range 18-45 years) receiving mitotane at a median initial dose of 3 g/day (range 1.5-6 g/day).

METHODS

Gynecological history was collected and ovarian ultrasound was performed. Four women also underwent ovarian CT or magnetic resonance imaging. Serum gonadotropin, estradiol (E2), androgens, sex hormone-binding globulin (SHBG), and circulating mitotane levels were determined at diagnosis and during mitotane therapy.

RESULTS

In the women included, ovarian macrocysts (bilateral in 51%) were detected after a median 11 months (range: 3-36) of mitotane exposure. The median number of macrocysts per woman was two (range: 1-4) and the median diameter of the largest cysts was 50 mm (range: 26-90). Menstrual irregularities and/or pelvic pain were present in 15 out of 21 women at macrocyst diagnosis. In two women, the macrocysts were revealed by complications (ovarian torsion and hemorrhagic macrocyst rupture) that required surgery. Mitotane therapy was associated with a significant decrease in androstenedione and testosterone levels and a significant increase in LH levels. Serum FSH and E2 levels were also increased, and SHBG levels rose markedly.

CONCLUSIONS

Mitotane therapy causes significant morphological and ovarian/gonadotrope hormonal abnormalities in premenopausal women. Follicular thecal steroid synthesis appears to be specifically altered and the subsequent increase in gonadotropins might explain the development of macrocysts. The mechanisms underlying these adverse effects, whose exact prevalence in this population still needs to be determined, are discussed.

Effective ovarian stimulation in a patient with resistant ovary syndrome and antigonadotrophin antibodies

PROBLEM

We report on a successful ovarian stimulation and pregnancy in a patient with 'resistant ovary syndrome' (ROS) and antigonadotrophin antibodies. ROS is characterized by high endogenous gonadotrophins, low estradiol, normal ovarian antral follicle counts and normal antimuellerian hormone values.

METHOD OF STUDY

After cyclical hormone treatment, downregulation with GnRH analogue and ICSI procedure followed. Granulosa cells were treated with LH, FSH or hMG and expression of receptors for FSH, LH, oestrogen receptor beta (ERb) and progesterone receptor A (PR-A) was determined. Serum of the patient was analysed for antibodies directed against hMG.

RESULTS

After fertilization of ten metaphase II oocytes and transfer of two blastocysts, a singleton pregnancy was established. Stimulation of granulosa cells with FSH, LH and hMG upregulated ERb and PR-A. Dot blot analysis showed strong reactivity with hMG but not with recFSH.

CONCLUSION

This patient with normal expression of gonadotrophin receptors showed antibodies directed to hMG but not to recFSH.

[Phenotype-genotype correlation in mutations of the gonadotrophin receptor gene in women]

Different mutations have been described in LH and FSH genes as well as in their receptors. These mutations are either activating (gain of function), or inhibiting (loss of function). Activating mutations are expressed as a dominant trait, thus in the heterozygous state, whereas inhibiting mutations are only expressed when both alleles bear the mutation. Inactivating mutations of FSH receptor gene, in women, are associated with primary ovarian insufficiency. Inactivating mutations of LH receptor gene have also been described, most often in XX patients whose families also include cases of male pseudohermaphrodism. Clinically, these women suffer from primary amenorrhea but with normal development of breasts and the hair system. Infertility is constant. LH blood levels are increased, estradiol blood levels are those encountered at the beginning of the follicular phase (50-70 pg/ml). The discovery of these mutations allows a better understanding of some genotypes and is helpful in advancing our knowledge of these receptors.

A new LH receptor splice mutation responsible for male hypogonadism with subnormal sperm production in the propositus, and infertility with regular cycles in an affected sister

BACKGROUND

Inactivating LH receptor (LHR) mutations have been described so far in men as well as in women. Phenotypes in men have been variable with in nearly all cases impairment of sex differentiation or azoospermia. We report a milder reproductive phenotype both in a male patient and his sister.

METHODS AND RESULTS

We describe a family that carries a homozygous mutation G-->A at position -1 at the intron 10-exon 11 boundary of the LHR gene. The male patient presented with delayed puberty, micropenis and oligospermia. Two of his sisters were homozygous for the same mutation and were infertile. Surprisingly, one of them was found to have had regular ovarian cycles for years and showed normal LH values (6.5 and 10.6 mIU/ml for LH and FSH, respectively). In vitro analysis showed that this altered splicing resulted in an LHR from which eight amino acids are deleted from the extracellular domain (Delta Tyr(317)-Ser(324)). In vitro expression has shown that the receptor was expressed and capable of LH-induced signaling, albeit with reduced potency (P < 0.001).

CONCLUSIONS

LHR mutations may represent an underestimated cause of infertility in women, in addition to being responsible for male hypogonadism with reduced spermatogenesis.

Neoplasms and pathology of sexual developmental disorders (intersex)

Continuing new insights into the biology of sexual development and advances in chromosome analysis have led to early identification and prompt treatment of the intersexual patient, the results of which facilitate a more normal life for affected individuals. Based on these advances, a classification of abnormal sexual development has been developed and refined that correlates the gonadal and genital anatomy with the chromosomal findings and specific genetic or metabolic defects. In a shift from a classification anchored on whether the intersex revolves about a specific gene or whole chromosomal abnormality, the current classification is organised by broader categories into which the intersexual disorders are divided into 'abnormalities of genital differentiation', due largely to the abnormal production or sensitivity of a single hormone, or 'abnormalities in sex determination', due to abnormal gonadal differentiation, usually testicular, with or without chromosomal aberration. The current classification is an integrated approach to this complex group of disorders and is organised according to the manner by which patients present as well as on the pathophysiological basis of the defect. The classification also groups patients who are at high risk for development of gonadal neoplasia.

[Leydig cell hypoplasia]

The Leydig cell hypoplasia is a rare and well defined form of male pseudohermaphroditism with autosomal recessive inheritance pattern. An inadequate fetal testicular Leydig cell differentiation and, consequently a low androgenic production during intra uterine and post natal periods, result in absence or incomplete virilization in patients with 46,XY karyotype. These patients exhibit a wide clinical spectrum, ranging from complete female external genitalia to male external genital with micropenis, low serum testosterone levels associated with high LH levels. Inactivating mutations of the LH/hCG receptor gene have been identified in affected families in the last decade. However, the low frequency of inactivating mutations in this gene, and the lack of segregation of intragenic polymorphisms among affected members from families with typical phenotype of Leydig cell hypoplasia, suggest the genetic heterogeneity of this condition.

Distinct mechanisms of cAMP induction by constitutively activating LH receptor and wild-type LH receptor activated by hCG

Asp578Gly is the major mutation of luteinizing hormone (LH) receptors in humans. It is a dominant mutant, constitutively activates Galphas, and induces cAMP production in the absence of the cognate hormone, causing the familial male precocious puberty. The mechanism of the elevated basal cAMP level is unclear. Our data show strikingly different mechanisms between the elevated basal cAMP induced by the activating mutant and the cAMP induced by the wild-type receptor activated by human chorionic gonadotropin (hCG) binding. The study suggests an approach to attenuating the elevated basal cAMP of the activating mutant LH receptor, which could be useful for controlling the familial male precocious puberty. For the study, we used the C-terminal peptides of Galphas and Galphai2, which couple to the receptor.

The genetics of male undermasculinization

A review of the genetics of male undermasculinization must encompass a description of the embryology of the genital system. The dimorphism of sex development consequent upon the formation of a testis and the subsequent secretion of hormones to impose a male phenotype is highlighted. Thus, an understanding of the causes of male undermasculinization (manifest as XY sex reversal, complete and partial) includes reviewing the genetic factors which control testis determination and the production and action of testicular hormones. The study of disorders of male sex development has contributed substantially to knowledge of normal male development before birth. This knowledge has been complimented in recent years by the use of targeted murine gene disruption experiments to study the sex phenotype, although murine and human phenotypes are not always concordant. The investigation of disorders associated with male undermasculinization of prenatal onset is described briefly to complete the review.

Male pseudohermaphroditism due to inactivating luteinizing hormone receptor mutations

Human male sexual development is regulated by chorionic gonadotropin (CG) and luteinizing hormone (LH), the action of both mediated by the LH receptor (LHR). Mutations that inactivate the LHR cause Leydig cell hypoplasia (LCH), an autosomal recessive disorder. In its mild form, LCH patients present with male hypogonadism. In its severe form, patients present with male pseudohermaphroditism, with female external genitalia, and cryptorchid testis. Mullerian derivatives are absent. Histological examination of the testis shows absence of mature Leydig cells. LCH patients have elevated plasma levels of LH, normal-to-elevated levels of follicle stimulating hormone (FSH), and low levels of testosterone that do not respond to CG stimulation. Missense mutations, nonsense mutations, deletion mutations, and in-frame insertion mutation of the LHR have been identified in patients with LCH. These mutations are not localized in any particular region of the gene and cause variable degrees of receptor-activity loss. The clinical manifestation of patients with LCH with homozygous or compound heterozygous mutations can be correlated with the residual activity of their respective mutated LHRs. Homozygous inactivating mutations of the LHR in the female cause hypergonadotrophic hypogonadism with primary amenorrhea or oligoamenorrhea, cystic ovaries, and infertility.