Effects of androgens on bioactivity and immunoreactivity of pituitary FSH in GnRH antagonist-treated male rats

Effects of castration on androgen receptors and gonadotropins in the pituitary of adult male viscachas

The aims of the present study were to determine whether castration results in quantitative immunohistochemical changes in androgen receptors (AR), LH-immunoreactive (IR) cells and FSH-IR cells, and to analyse the colocalisation of AR and gonadotropins in the pituitary pars distalis (PD) of viscachas. Pituitaries were processed for light and electron microscopy. AR-IR, LH-IR and FSH-IR cells were detected by immunohistochemistry. In morphometric studies, the percentage of AR-IR, LH-IR, FSH-IR, LH-IR/AR-IR and FSH-IR/AR-IR cells was determined. In intact viscachas, AR were distributed throughout the PD; they were numerous at the caudal end, with intense immunostaining. LH-IR cells and FSH-IR cells were found mainly in the ventral region and at the rostral end of the PD. Approximately 45%-66% of LH-IR cells and 49%-57% of FSH-IR cells expressed AR in the different zones of the PD. In castrated viscachas, there was a significant decrease in the percentage of AR-IR, LH-IR, FSH-IR, and FSH-IR/AR-IR cells. Some pituitary cells from castrated viscachas also exhibited ultrastructural changes. These results provide morphological evidence that gonadal androgens are directly related to the immunolabelling of AR, LH and FSH. Moreover, the colocalisation of AR and FSH is most affected by castration, suggesting the existence of a subpopulation of gonadotrophs with different regulatory mechanisms for hormonal synthesis, storage and secretion.

Metformin versus flutamide in the treatment of metabolic consequences of non-obese young women with polycystic ovary syndrome: a randomized prospective study

In addition to the reproductive consequences, polycystic ovary syndrome (PCOS) is characterized by a metabolic disorder in which hyperinsulinemia and insulin resistance are central features. The effects and possible benefits from insulin-sensitizing drugs are not well known, especially in non-obese women with PCOS. This study was designed to evaluate the effects of metformin and flutamide on metabolic parameters and insulin resistance in non-obese women with PCOS. Thirty non-obese women newly diagnosed with PCOS and 15 age- and weight-matched healthy volunteers as controls were included in the study. Patients were assigned randomly to receive flutamide 250 mg daily or metformin 850 mg three times daily. Glucose, insulin, insulin resistance, androgen levels and glucose and insulin responses to an oral glucose tolerance tests (OGTT) were assessed before and after a 4-week therapy period. A positive correlation was found between body mass index and insulin level in patients with PCOS and controls. Follicle stimulating hormone, luteinizing hormone, free testosterone and dehydroepiandrosterone sulfate levels decreased significantly, but insulin resistance levels were not changed after flutamide therapy. Body weight, free testosterone, insulin and insulin resistance levels decreased significantly after metformin therapy. In conclusion, metformin treatment improved insulin sensitivity and decreased androgen levels, and flutamide decreased androgen levels but failed to improve insulin sensitivity in the non-obese women with PCOS.

Endocrine regulation of gonadotropin glycosylation

The pituitary gonadotropins--luteinizing hormone and follicle-stimulating hormone--as well as the placental choriogonadotropin belong to the family of glycoprotein hormones. These structurally related hormones, which regulate several major reproductive functions of the body, are heterodimers consisting of a common alpha-subunit noncovalently bound to a beta-subunit. The N- and O-linked oligosaccharide chains of these gonadotropins play an important role in intracellular folding, assembly, secretion, metabolic clearance, and biological activity of the hormone. Gonadotropin glycosylation is a highly complex process; within the gonadotropes it is modulated by a variety of extrapituitary factors of hypothalamic and gonadal origin. In particular, estrogens and androgens appear to regulate terminal sialylation and/or sulfation of the oligosaccharide attachments and hence some functional properties of the gonadotropin molecule determined by these residues, i.e., metabolic clearance and in vivo biopotency. Through these extrapituitary inputs, the anterior pituitary may not only regulate the quantity but also the quality of the gonadotropin signal delivered to the gonads in a given physiologic or pathologic condition.

Molecular heterogeneity of serum follicle-stimulating hormone in hypogonadal patients before and during androgen replacement therapy and in normal men

OBJECTIVE

The present study was performed to characterize the molecular heterogeneity of serum FSH in normal males and to investigate the possible influence of testosterone on serum FSH in androgen-deficient men before and during testosterone administration.

DESIGN AND PATIENTS

Serum samples were taken at 10-minute intervals between 0730 and 0830 h from nine healthy, eugonadal men and from eight men with primary hypogonadism (Klinefelter's syndrome). In the hypogonadal patients, sampling was performed before treatment (n = 8), 4-5 days after the first and the third injection of 250 mg testosterone enanthate given intramuscularly at three-weekly intervals (n = 6), as well as 3 months after the onset of therapy (n = 3). Sampling was repeated 7 days apart in two of the nine healthy volunteers.

MEASUREMENTS

Aliquots from the individual serum samples were pooled and fractionated by chromatofocusing in the pH range 6-3. Immunoreactive FSH was measured by immunofluorometric assay (IFMA) in each fraction and the individual serum samples. In each serum pool, bioactive FSH was determined by in-vitro bioassay (rat Sertoli cell aromatase bioassay), testosterone by RIA and LH by IFMA.

RESULTS

After grouping the percentage of immunoreactive FSH recovered in the individual fractions into intervals of 0.5 pH units, significant differences between controls and patients were observed in the pH regions 4-4.5, 5.5-6 and 6-6.5. No statistically significant changes in the isoform distribution of FSH were detected during therapy in the Klinefelter patients. A high degree of variability, which did not follow a common pattern, was observed in the isoform distribution of FSH within the same individuals, both in the hypogonadal patients during treatment and in the two normal men whose blood samples were taken on two different occasions.

CONCLUSIONS

Serum FSH is highly heterogeneous in normal and hypogonadal men. There is a spontaneous intra-individual variability in the relative abundance of the different FSH isoforms in serum that may most probably be related to metabolic deglycosylation of FSH. Minor but significant differences in the molecular heterogeneity of serum FSH could be demonstrated in Klinefelter patients compared to normal men. These differences are not modified by administration of testosterone enanthate at doses achieving normal androgenization, suggesting that factors different from testosterone may modulate FSH pleomorphism.

Effects of antiandrogens and ethane dimethane sulphonate (EDS) on gene expression, free subunits, bioactivity and secretion of pituitary gonadotrophins in male rats

In the male rat, testosterone has been shown to regulate gonadotrophin synthesis and secretion under experimental conditions such as castration or gonadotrophin-releasing hormone (GnRH) antagonist with or without testosterone. The present study aims at clarifying the effects of non-steroidal antiandrogens, Casodex and flutamide, and ethane dimethane sulphonate (EDS) on the regulation of gonadotropin synthesis and secretion. To enable a direct comparison within this study to expected effects of testosterone, a GnRH antagonist-treated group and a castrated group were included. The gene expression of the subunits was correlated with changes in the pituitary and plasma content of immunoreactive luteinizing hormone (LH) and follicle-stimulating hormone (FSH), free subunits and pituitary content of in vitro bioactive LH and FSH. Groups of ten male rats each received the following treatments for 7 days: (1) vehicle; (2) castration; (3) EDS (75 mg/kg); (4) GnRH antagonist (Cetrorelix 250 micrograms/kg/day), (5) Casodex (20 mg/kg/day) or (6) flutamide (20 mg/kg/day). The effectiveness of testosterone deprivation was demonstrated by the reduction of weight in androgen-dependent organs such as epididymides and seminal vesicles in the treated groups. Treatment with flutamide, EDS or castration significantly increased (p < 0.05) serum levels of LH, FSH and alpha-subunit, whereas serum gonadotrophin levels were decreased in the GnRH antagonist-treated group. alpha-Subunit mRNA levels were elevated in the castrated, EDS and flutamide group and LH-beta mRNA levels were increased in the castrated and EDS group. FSH-beta mRNA levels were increased in the castrated group and decreased in the GnRH antagonist group, but remained unchanged in the flutamide and EDS group.(ABSTRACT TRUNCATED AT 250 WORDS)