SJ Meachem, E Nieschlag and M Simoni
The recent availability of specific inhibin assays has demonstrated that inhibin B is the relevant circulating inhibin form in the human male. Inhibin B is a dimer of an alpha and a betaB subunit. It is produced exclusively by the testis, predominantly by the Sertoli cells in the prepubertal testis, while the site of production in the adult is still controversial. Inhibin B controls FSH secretion via a negative feedback mechanism. In the adult, inhibin B production depends both on FSH and on spermatogenic status, but it is not known in which way germ cells contribute to inhibin B production. The regulation of inhibin B production changes during life. There is an inhibin B peak in serum shortly after birth only partly correlated with an increase in serum FSH, probably reflecting the proliferating activity of the Sertoli cells during this phase of life. Afterwards, inhibin B levels decrease and remain low until puberty, when they rise again, first as a consequence of FSH stimulation and then as a result of the combined regulation by FSH and the ongoing spermatogenesis. In the adult, serum inhibin B shows a clear diurnal variation closely related to that of testosterone. The administration of FSH increases the secretion of inhibin B in normal men, but is much more pronounced in males with secondary hypogonadism. The treatment of infertile men with FSH, however, does not result in an unequivocal inhibin B increase. There is a clear inverse relationship between serum inhibin B and FSH in the adult. Serum inhibin B levels are strongly positively correlated with testicular volume and sperm counts. In infertile patients, inhibin B decreases and FSH increases. In general, there is very good correlation with the degree of spermatogenetic damage, with the arrest at the earlier stages having the lowest inhibin B levels. However, for unknown reasons, there are cases of Sertoli-cell-only syndrome with normal inhibin B levels. Inhibin B and FSH together are a more sensitive and specific marker for spermatogenesis than either one alone. However, the inhibin B concentrations are not a reliable predictor of the presence of sperm in biopsy samples for testicular sperm extraction. Suppression of spermatogenesis with testosterone and gestagens leads to a partial reduction of inhibin B in serum but it is never completely suppressed. In contrast, testicular irradiation in monkeys or humans leads to a rapid and dramatic decrease of inhibin B, which becomes undetectable when germ cells are completely absent. In summary, although inhibin B is a valuable index of spermatogenesis, the measurement of serum inhibin B levels is still of limited clinical relevance for individual patients.
M Depenbusch, S von Eckardstein, M Simoni and E Nieschlag
OBJECTIVE: It is generally accepted that both gonadotropins LH and FSH are necessary for initiation and maintenance of spermatogenesis. We investigated the relative importance of FSH for the maintenance of spermatogenesis in hypogonadotropic men. SUBJECTS AND METHODS: 13 patients with gonadotropin deficiency due to idiopathic hypogonadotropic hypogonadism (IHH), Kallmann syndrome or pituitary insufficiency were analyzed retrospectively. They had been treated with gonadotropin-releasing hormone (GnRH) (n=1) or human chorionic gonadotropin/human menopausal gonadotropin (hCG/hMG) (n=12) for induction of spermatogenesis. After successful induction of spermatogenesis they were treated with hCG alone for maintenance of secondary sex characteristics and in order to check whether sperm production could be maintained by hCG alone. Serum LH, FSH and testosterone levels, semen parameters and testicular Volume were determined every three to six Months. RESULTS: After spermatogenesis had been successfully induced by treatment with GnRH or hCG/hMG, hCG treatment alone continued for 3-24 Months. After 12 Months under hCG alone, sperm counts decreased gradually but remained present in all patients except one who became azoospermic. Testicular Volume decreased only slightly and reached 87% of the Volume achieved with hCG/hMG. During treatment with hCG alone, FSH and LH levels were suppressed to below the detection limit of the assay. CONCLUSION: Once spermatogenesis is induced in patients with secondary hypogonadism by GnRH or hCG/hMG treatment, it can be maintained in most of the patients qualitatively by hCG alone, in the absence of FSH, for extended periods. However, the decreasing sperm counts indicate that FSH is essential for maintenance of quantitatively normal spermatogenesis.
M. Simoni, S. A. Khan, Ch. De Geyter and E. Nieschlag
Effects of serum from pregnant women on basal and FSH (or cAMP) stimulated aromatase activity of immature rat Sertoli cells in primary culture were studied. Pregnancy serum caused a dose-dependent stimulation of Sertoli cell aromatase activity and the response curves were parallel to those obtained with human FSH. This stimulatory (FSH-like) activity increased progressively during pregnancy, with a sharp drop immediately after delivery. However, the FSH-like bioactivity was not associated with immunoreactive FSH when a specific radioimmunoassay was employed. On the other hand, serum from pregnant women caused a dose-dependent inhibition of FSH and dibutyryl-cAMP-stimulated aromatase activity. These data suggest that human pregnancy serum contains factor(s) which may stimulate basal aromatase activity of Sertoli cells and may inhibit FSH-induced aromatase activity. These factors, most probably of placental origin, may play a role in the regulation of estrogen production during gestation.
M. SIMONI, S. KHAN, CH. DE GEYTER and E. NIESCHLAG
A Kamischke, M Simoni, K Schrameyer, A Lerchl and E Nieschlag
OBJECTIVE: This study aims to investigate the pharmacodynamic effect of FSH on inhibin B serum levels in normal men in order to elucidate the physiological regulation of inhibin B secretion in more detail. DESIGN AND METHODS: Injections of 3000 IU recombinant, human FSH (rhFSH) were followed by single-blinded injections of placebo, 1000 and 2000 IU rhFSH spaced by at least 28 days between injections. RESULTS: After injection of 3000 IU rhFSH, inhibin B values were significantly elevated above baseline for 24, 96 and 120 h (maximal increase after 96 h, mean +/- s.e.m. 303+/-18 pg/ml). Injection of 2000 IU rhFSH led to a significant increase in inhibin B (maximum mean +/- s.e.m. 318+/-20 pg/ml) from 24 to 120 h. Injection of 1000 IU rhFSH led to a significant increase in inhibin B after 96 h (maximum mean +/- s.e.m. 300+/-16 pg/ml). The inhibin B areas under the curve after injection of 2000 and 3000 IU rhFSH were significantly higher than those following the placebo and 1000 IU rhFSH. In the 12 fertile men investigated, at baseline a strong diurnal rhythm of inhibin B parallel to that of testosterone was observed. CONCLUSIONS: Serum inhibin B can be considered only a partial pharmacodynamic parameter of FSH in vivo, since the integrity of the spermatogenic process appears to be a second fundamental component in the regulation of its secretion from the testis.
T Vihtamaki, M Simoni, R Tuimala, E Nieschlag and KK Vihko
OBJECTIVE: The purpose of the present study was to evaluate the hormonal profile of patients of postmenopausal age during estrogen replacement therapy (ERT) with special reference to the serum levels of biologically active FSH (B-FSH) in a self-adjusted ERT model. DESIGN: The hormonal values found have been correlated to climateric symptoms reported by the patients (scored by the Kupperman menopausal index (KI)). METHODS: B-FSH was measured using an assay based on a cell system transfected permanently with FSH receptor cDNA. All women (n=32) applied estradiol percutaneously using 1 mg estradiol-17beta (E(2)) as an initial dose and were encouraged to increase the daily dose until they felt comfortable according to a specific scheme. Twelve of the 32 women were hysterectomized and treated, accordingly, with ERT only; 20 women received megestrol acetate monthly for 10 days. RESULTS: The initial average KI was 30 (range 10-54). A high degree of correlation (r=0.83; P<0.001) was observed between B-FSH and immunologically active FSH (I-FSH). Serum I-FSH and E(2) correlated negatively (r=-0.21; P<0.001); similarly, a negative correlation (r=-0.15; P<0.01) was observed between serum B-FSH and E(2) levels. Serum I-FSH and KI showed modest but significant positive correlation (r=0.13; P<0.01); a somewhat higher degree of correlation (r=0.19; P<0.005) was observed when B-FSH and KI were compared. E(2) showed positive correlation to serum sex-hormone binding globulin levels (r=0.22; P<0.001). CONCLUSIONS: This study shows that the transdermal self-adjusted hormone replacement therapy (HRT) model introduced is suitable for studies on endocrine changes during postmenopausal ERT. The finding of poor correlation between serum E(2) levels and KI emphasizes the importance of hormonal measurements during postmenopausal HRT.
Ramesh K. Chandolia, Gerhard F. Weinbauer, Manuela Simoni, Hermann M. Behre and Eberhard Nieschlag
The effects of chronic blockade of androgen action by the antiandrogens flutamide and Casodex on serum and pituitary concentrations of LH and FSH, serum and testicular androgen levels, reproductive organ weights, and on spermatogenesis were compared in the adult rat. Animals were treated for 3 and 8 weeks with vehicle, Casodex (20 mg · kg−1 · (day)−1, flutamide (20 mg · kg−1 · (day)−1) and GnRH antagonist (150 μg/day, Detirelix). Treatment with GnRH antagonist suppressed gonadotropin and testosterone production, reduced the weights of testes, epididymides and seminal vesicles, and inhibited germ cell development. Flutamide administration markedly elevated serum and pituitary levels of gonadotropins as well as serum and testicular androgen concentrations. Casodex-induced elevation of gonadotropin concentrations was less pronounced and serum and testicular levels of androgens did not change significantly. The reduction of seminal vesicle weights was similar after Casodex and GnRH antagonist treatment, whereas flutamide was less effective. Testicular weight and spermatogenesis (assessed by light microscopical and flow-cytometric analysis) remained unaffected by Casodex and flutamide. It is concluded, that 1. Casodex, in contrast to flutamide, is a peripherally selective antiandrogen, and 2. Casodex influences release of gonadotropins into circulation less than flutamide. Therefore this antiandrogen might be useful clinically for selectively blocking androgen actions in the accessory sex glands.
Fabio Lanfranco, Jörg Gromoll, Sigrid von Eckardstein, Eva M Herding, Eberhard Nieschlag and Manuela Simoni
Objective: To determine the frequency of mutations of the gonadotropin-releasing hormone receptor (GnRHR) and of the G protein-coupled receptor 54 (GPR54) genes in normosmic idiopathic hypogonadotropic hypogonadism (IHH).
Methods: In a retrospective study we analyzed the GnRHR and the GPR54 genes of 45 IHH patients and 50 controls. Genomic DNA was amplified by PCR to obtain partially overlapping amplicons encompassing the exon–intron boundaries of the GnRHR and GPR54 genes and analyzed by single-stranded conformation polymorphism gel electrophoresis and/or DNA sequencing.
Results: One heterozygous R262Q mutation of the GnRHR gene was identified in one patient with familial IHH. The silent single-nucleotide polymorphism (SNP) 453C > T occurred at the same frequency in patients and controls. One patient with sporadic IHH and consanguineous parents showed a novel homozygous sequence variation of the GPR54 gene (1001_1002insC) resulting in an open reading frame shift and elongation of 43 amino acids with an increased number of proline residues in the intracellular receptor domain. This patient had delayed puberty, low testosterone (3.4 nmol/l), and low-normal LH and FSH levels responsive to GnRH. Pulsatile GnRH administration normalized testosterone levels and induced spermatogenesis sufficiently to induce a pregnancy with assisted reproduction. Two common SNPs in exon 1 and exon 5 of the GPR54 gene showed similar frequency distribution and hormonal profiles in IHH and controls.
Conclusions: Mutations of the GnRHR and of the GPR54 gene are rare in IHH and should be investigated especially in cases with autosomal recessive transmission. Common SNPs of the GnRHR and GPR54 genes do not play any role in IHH.
Manuela Simoni, Jörg Peters, Hermann M Behre, Sabine Kliesch, Eckhard Leifke and Eberhard Nieschlag
Simoni M, Peters J, Behre HM, Kliesch S, Leifke E, Nieschlag E. Effects of gonadotropin-releasing hormone on bioactivity of follicle-stimulating hormone (FSH) and microstructure of FSH. luteinizing hormone and sex hormone-binding globulin in a testosterone-based contraceptive trial: evaluation of responders and non-responders. Eur J Endocrinol 1996;135:433–9. ISSN 0804–4643
Only a proportion of normal men participating in testosterone-based contraceptive trials develop azoospermia (responders). This study analyzed whether serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and sex hormone-binding globulin (SHBG) are qualitatively different between responders and non-responders. Determination of in vitro bioactive FSH after stimulation with gonadotropin-releasing hormone (GnRH) and analysis of molecular heterogeneity of serum FSH. LH and SHBG was carried out by chromatofocusing and concanavalin-A affinity chromatography in eight men who had participated in a previous contraceptive study with testosterone buciclate. Blood was withdrawn at 15-min intervals on two basal occasions and 30, 45 and 60 min after iv administration of GnRH (100 μg). Pools of sera were separated by chromatofocusing in the pH range 3–6 and by lectin chromatography on concanavalin A. Immunoreactive FSH, LH and SHBG were assayed in the eluates. Bioactive FSH was analyzed by the rat Sertoli cell bioassay. Serum bioactive FSH increased after GnRH stimulation, without significant differences between responders and non-responders. The chromatofocusing profiles of serum FSH showed a significant shift towards the less acidic region after GnRH. The isoform distribution was similar in responders and non-responders. No significant differences were found in the relative proportion of FSH, LH and SHBG retained by concanavalin A. It is concluded that the extent of suppression of sperm production by androgen administration cannot be foreseen either on the basis of the response of bioactive FSH to GnRH administration or from the glycosylation pattern of serum FSH, LH and SHBG.
E Nieschlag, Institute of Reproductive Medicine of the University, Domagkstr. 11, D-48129 Münster, Germany