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PubMed1991

Human follicular fluid contains a follicle-stimulating hormone (FSH) receptor binding inhibitor which has FSH agonist activity, is immunologically similar to FSH, but can be distinguished from FSH.

We have previously reported the presence in human follicular fluid (hFF) of a high (greater than 5000) mol wt FSH receptor binding inhibitor (FSH-BI). This hFF FSH-BI was further purified by removal of material insoluble in acidified acetone (pH 4.1) but soluble in diethyl ether (pH 10.5), followed by molecular sieving through Sephacryl S-100. FSH-BI activity eluted from S-100 with an elution volume similar to that of hFSH, but could be distinguished from hFSH on the basis of a differential sensitivity to acid inactivation. Human FSH was inactivated in acetone at pH 4.1 (1 h, 25 C), whereas hFF FSH-BI retained activity under these conditions. Human FF FSH-BI also demonstrated FSH-like agonist activity, defined as the ability to stimulate basal levels of estradiol synthesis in cultured rat Sertoli cells. Human FSH-BI strongly cross-reacted to a commercially available monoclonal antibody used to measure serum hFSH. Indeed, recovery of FSH immunologic activity was significantly greater (134-fold on a mass basis) after partial purification, indicating that antibody recognition sites were apparently masked in unfractionated hFF. In summary, large mol wt hFSH-BI has been partially purified from hFF and found to be similar in size to pituitary hFSH and to have FSH-like agonist activity in vitro. Although distinguishable from pituitary hFSH on the basis of stability to acid, hFSH-BI appears immunologically related to pituitary hFSH so that measurements of hFSH levels in hFF using immunologic techniques should be interpreted with caution.

Acetone↗

PubMed1985

CI628 inhibits follicle-stimulating hormone (FSH)-induced increases in FSH receptors of the rat ovary: requirement of estradiol for FSH action.

Although estradiol (E2) alone does not increase receptors for FSH in granulosa cells, E2 priming before administration of FSH increases numbers of FSH receptors significantly compared with FSH alone. We hypothesized that if E2 is required for FSH to increase its own receptor, blocking estrogen action should prevent FSH-induced increases in FSH receptors. Five groups of hypophysectomized rats were injected sc with: saline at 0 h; the antiestrogen CI628 (1 mg) at -6 h; human FSH (hFSH, 2 micrograms) at 0 h; CI628 at -6 h, then hFSH at 0 h; and CI628 plus E2 (2 mg) at -6 h, then FSH at 0 h. Animals were decapitated at 0, 6, 12, or 24 h, and granulosa membrane receptors for FSH, LH, and nuclear receptors for E2 were measured. LH receptor levels increased only after administration of E2 before hFSH. Treatment with hFSH for 6 h increased numbers of FSH receptors 3-fold (P less than 0.01) without any increase in numbers of E2 receptors. At 12 and 24 h, hFSH increased numbers of FSH and E2 receptors 6- and 7-fold (P less than 0.01) over controls. CI628 prevented the hFSH-induced increases in FSH receptors at 6, 12, and 24 h. Administration of E2 concomitant with CI628 before hFSH significantly reversed the inhibitory effects of CI628 on hFSH-induced increases in FSH receptors. There were no changes in affinity of FSH or E2 receptors from 0 to 24 h. To determine whether E2 was acting on the adenylate cyclase system, the ability of hFSH to increase the content of cAMP in granulosa cells in each treatment group was determined. After an iv injection of hFSH, cAMP levels were similar in CI628- and saline-treated rats but had increased 6-fold (P less than 0.01) in hFSH or CI628 plus hFSH-treated animals. Thus, blocking hFSH-induced increases in FSH and E2 receptor appeared to have no effect on FSH stimulation of cAMP. In conclusion E2 appears to be required for FSH action, perhaps by acting within granulosa cells distal to the cAMP-adenylate cyclase system.

Animals↗

PubMed1998

The follicle-stimulating hormone (FSH) threshold/window concept examined by different interventions with exogenous FSH during the follicular phase of the normal menstrual cycle: duration, rather than magnitude, of FSH increase affects follicle development.

According to the threshold concept, FSH concentrations need to surpass a distinct level to stimulate ovarian follicle growth. The window concept stresses the significance of a limited duration of elevated FSH levels above the threshold for single dominant follicle selection. The aim of this study was to investigate effects on follicle growth of increased FSH levels, differing in duration and magnitude of elevation, during the follicular phase. Twenty-three normo-ovulatory (cycle length, 26-31 days), young (age, 20-31 yr) women volunteered for this study. In all subjects a series of daily transvaginal sonography scans of the ovaries and blood sampling [for FSH and estradiol (E2) determinations] were performed during two consecutive cycles. The first study cycle (control cycle) started 10 days after urinary assessment of the LH surge in the preceding cycle (DayLH) and was concluded on the day of ovulation assessed by transvaginal sonography scans. The second series of daily monitoring (intervention cycle) started 10 days after DayLH in the control cycle. After randomization, subjects received either 375 IU urinary FSH, s.c., as a single injection on Day(LH+14) (group A; n = 11) or 75 IU daily from Day(LH+19) until Day(LH+23) (group B; n = 12). In group A, FSH levels increased on the day after injection to a median concentration of 10.1 IU/L, which was 1.9 times higher (P < 0.01) than levels on matching days during the control cycle. Concentrations returned to basal levels 3 days after injection. In group B, a moderate elevation of FSH concentrations (15% increase; P < 0.05) was observed compared to levels during the control cycle. In group A, E2 concentrations increased (P = 0.03) 1 day after FSH injection and returned to baseline levels within 2 days. In group B, E2 levels started to increase after the first injection of FSH and remained significantly higher (P < 0.01) during the following 5 days compared to those on matching days in the control cycle. Compared to matching days in the control cycle an increased number of follicles 8-10 mm in size was found in group A (P < 0.01) during the period from Day(LH+14) until Day(LH+19), without an increase in follicles 10 mm or larger thereafter. In contrast, in group B, the numbers of both 8- to 10-mm and 10-mm or larger follicles were higher during the period from Day(LH+19) until Day(LH+24) in group B (P = 0.02 and P < 0.01, respectively). Results from the present study suggest that a brief, but distinct, elevation of FSH levels above the threshold in the early follicular phase does not affect dominant follicle development, although the number of small antral follicles did increase. In contrast, a moderate, but continued, elevation of FSH levels during the mid to late follicular phase (effectively preventing decremental FSH concentrations) does interfere with single dominant follicle selection and induces ongoing growth of multiple follicles. These findings substantiate the FSH window concept and support the idea of enhanced sensitivity of more mature follicles for stimulation by FSH. These results may provide the basis for further investigation regarding ovulation induction treatment regimens with reduced complication rates due to overstimulation.

Adult↗

PubMed2003

Novel genes modulated by FSH in normal and immortalized FSH-responsive cells: new insights into the mechanism of FSH action.

Follicle-stimulating hormone (FSH) controls the development of follicle-enclosed oocytes in the mammalian ovary by interacting with specific receptors located exclusively on granulosa cells. Its biological activity involves stimulation of intercellular communication, intracellular signaling, and up-regulation of steroidogenesis; the entire spectrum of genes regulated by FSH is not yet fully characterized. We have established monoclonal rat FSH-responsive granulosa cell lines that express FSH receptors at 20-fold higher rates than with primary cells, and thus increased the probability of yielding a distinct spectrum of genes modulated by FSH. Using Affymetrix DNA microarrays, we discovered 11 genes not reported earlier to be up-regulated by FSH and 9 genes not reported earlier to be down-regulated by FSH. Modulation of signal transduction associated with G-protein signaling, phosphorylation of proteins, and intracellular-extracellular ion balance was suggested by up-regulation of decay accelerating factor GPI-form precursor (DAF), membrane interacting protein RGS16, protein tyrosine phosphatase (PTPase), oxidative stress-inducible protein tyrosine phosphatase (OSIPTPase), and down-regulation of rat prostatic acid phosphatase (rPAP), Na+, K+-ATPase, and protein phosphatase 1beta. Elevation in granzyme-like proteins 1 and 3, and natural killer (NK) cell protease 1 (NKP-1) along with reduction in carboxypeptidase E indicates possible FSH-mediated preparation of the cells for apoptosis. Up-regulation of vascular endothelial growth factors indicates the ability of FSH to produce angiogenic factors upon their maturation; whereas, reduction in insulin-like growth factor binding protein (IGFBP3) indicates its increased potential to promote p53-induced apoptosis. Striking similarities in FSH modulation of gene expression were found in primary cultures of human granulosa cells obtained from IVF patients although these cells expressed only 1% of FSH receptor compared with immortalized rat cells, as indicated by microarray technique, which probably is in the normal range of expression of this receptor in nontransformed cells. These findings should increase our understanding of the mechanism of FSH action in stimulating development of the ovarian follicular cells, of intracellular and intercellular communication, and of increasing the potential of ovarian follicular cells to undergo apoptosis during the process of selection of the dominant follicle.

Animals↗

PubMed1976

Secretion rates of LH and FSH during infusion of LH-FSH/RH in normal women and in patients with secondary amenorrhea: suggestive evidence for two pools of LH and FSH.

Normal women in the early follicular phase and in the luteal phase of the cycle, and patients with secondary amenorrhea received on consecutive days a rapid intravenous injection (50 mug) and a two or four-hour infusion (25 mug/h) of synthetic LH-FSH/RH. The responses of LH and FSH were evaluated by the measured plasma concentrations, as well as by the calculated pituitary secretion rates and by the amounts of hormone released. To estimate these pituitary secretion rates of LH and FSH, a simplified mathematical model is proposed. During an infusion of LH-FSH/RH the secretion rates of both LH and FSH increased in the three groups of women in a biphasic way with a dip after 1 to 2h of infusion, suggesting that besides the pool mobilized by a rapid intravenous injection of LH-FSH/RH there is a second pool of (stored) gonadotropins. For LH the increase above baseline concentrations was higher in group II (luteal phase) than in group I (follicular phase) or in group III (amenorrhea) and this both after a bolus injection and during infusion of LH-FSH/RH. For FSH a similar pattern of response prevailed during an infusion of LH-FSH/RH. After a bolus administration, however, the FSH release was relatively higher in group III (amenorrhea) than in both groups of normal women in which the increases were about the same. The latter finding suggests that the first pool of FSH is released by a different mechanism than the second pool.

Adult↗

PubMed1996

Pituitary and ovarian expression of the endogenous follicle-stimulating hormone (FSH) subunit genes and an FSH beta-subunit promoter-driven herpes simplex virus thymidine kinase gene in transgenic mice; specific partial ablation of FSH-producing cells by antiherpes treatment.

The ovarian expression of the endogenous follicle-stimulating hormone beta-subunit (FSH beta) and common alpha-subunit (C alpha) genes, and a herpes simplex virus thymidine kinase (tk) transgene, driven by a 2.3 kb bovine FSH beta promoter, was studied in normal and transgenic (tg) mice, tk functions not only as a neutral reporter that enables the study of the promoter function but also as an exogenously inducible toxigene. Reverse transcription-PCR followed by Southern blot hybridization with a nested probe was used to show the expression of the gene at the mRNA level. Common alpha-subunit mRNA was detected in the pituitary gland and ovaries of normal adult mice. We have previously detected endogenous FSH beta and tg tk mRNAs in the mouse pituitary, testis and ovary. In this study, the cellular localization of the corresponding proteins was visualized by immunocytochemistry. In normal mouse ovaries a positive reaction with FSH beta and C alpha antisera was seen in some of the corpora lutea and most prominently in the interstitial cells. A positive reaction with the tk antiserum was seen in the same cell types of tg mouse ovaries, but not in those of non-tg mice. Cell-ablation-inducing treatment (gancyclovir, 20 mg/kg per day, for 14 days) of tg female mice reduced pituitary FSH concentrations by 52% (P < 0.05) but did not affect pituitary LH or plasma gonadotropins compared with non-tg females treated in the same way. A longer period of cell ablation induction (acyclovir 400 mg/kg per day, for 21 days) reduced not only pituitary but also plasma FSH concentrations (55 and 57% respectively; P < 0.05) without affecting LH. This treatment also reduced ovarian weight by 38% (P < 0.01). In conclusion, our results show first that the endogenous FSH beta and C alpha proteins are produced in the mouse ovary. Hence, endogenously synthesized FSH or its subunits may have a role in the paracrine regulation of ovarian function. Secondly, the FSH beta promoter directs the expression of tg tk in the pituitary gonadotrope cells, as shown by specific but partial ablation of FSH-producing cells after induction by gancyclovir and acyclovir. In the ovary, tk protein was localized to the same compartments as the endogenous gonadotropin subunit proteins. This further confirms our finding of ovarian expression of the FSH subunit genes.

Acyclovir↗

PubMed1994

Follicle-stimulating hormone (FSH) increases FSH receptor messenger ribonucleic acid while decreasing FSH binding in cultured porcine granulosa cells.

The goal of the present studies was to compare direct effects of porcine FSH (pFSH) on [125I]pFSH-binding sites with effects of pFSH on FSH receptor mRNA in cultured porcine granulosa cells. Cells from immature follicles were cultured on laminin-coated plates in serum-free medium for up to 6 days in the absence or presence of pFSH (1-100 ng/ml) or cholera toxin (0.04-400 ng/ml), which activates adenylyl cyclase independently of the FSH receptor. RRA indicated that [125I] pFSH binding to cells cultured without stimulator increased more than 10-fold with time in culture. Addition of pFSH to cultures resulted in a dose-dependent decrease in binding, assessed after removal of bound pFSH. Equilibrium saturation binding analysis indicated that pFSH (10 ng/ml) caused a 39% decrease in binding sites in cells cultured for 6 days. At the same time, pFSH increased progesterone production 9.5-fold. Cholera toxin (4 ng/ml) increased [125I]pFSH binding 110% and progesterone production 8.9-fold. Northern hybridization analysis of cultured granulosa cell mRNA using a porcine FSH receptor cDNA revealed three transcripts for the FSH receptor [2.2, 3.5, and 4.2 kilobases (kb)], with the major transcript being 4.2 kb in length. Addition of either pFSH (10 ng/ml) or cholera toxin (10 ng/ml) to cultures of granulosa cells increased the intensity of pFSH receptor transcripts compared with control values, with the 4.2-kb message remaining predominant. Hybridization with a porcine LH receptor cDNA revealed different transcripts (2.4, 4.0, 4.7, 7.0, and 11.0 kb), with the major transcript being 4.7 kb in length. Addition of either pFSH or cholera toxin to the cultures increased the intensity of all LH receptor transcripts; however, cholera toxin was more effective than pFSH. pFSH and cholera toxin increased the intensity of each species to different extents, although the 4.7-kb transcript remained predominant. These results indicate that exposure to FSH in culture results in down-regulation of the FSH receptor. Down-regulation is accompanied by increased FSH receptor mRNA levels, suggesting that FSH enhances FSH receptor synthesis.

Animals↗

PubMed1990

A synthetic peptide corresponding to human FSH beta-subunit 33-53 binds to FSH receptor, stimulates basal estradiol biosynthesis, and is a partial antagonist of FSH.

We have previously shown that hFSH-beta 34-37 (KTCT) and 49-52 (TRDL) inhibit binding of 125I-hFSH to FSH receptor in calf testis membranes and that hFSH-beta 33-53, which encompasses these tetrapeptides, inhibits binding with increased potency. hFSH-beta 33-53 rapidly dimerizes under conditions utilized in the receptor binding assay (pH 7.5) so that the binding inhibition reported earlier was due to the hFSH-beta 33-53 dimer rather than the monomer. At pH 6.5, conversion to dimer does not occur, and binding inhibition could be unequivocally attributed to the monomer. Radioiodinated and alkylated hFSH-beta 33-53 binds to the FSH receptor with a Kd = (5.5 +/- 1.4) X 10(-5) M. The biological activity of hFSH-beta 33-53 was assessed by its ability to affect the conversion of androstenedione to estradiol in rat Sertoli cells cultures. FSH-beta 33-53 behaved as a partial antagonist of the FSH-induced estradiol synthesis. The required incubation medium, however, contains cystine as well as cystine, which rapidly forms a hFSH-beta Cys-(51)-S-S-Cys derivative at the pH of the incubation, 7.4. When hFSH-beta 33-53 was converted either to the hFSH-beta Cys(51)-S-S-Cys or to a carboxymethylated derivative, inhibition of FSH-induced estradiol synthesis still was observed. This result demonstrates that the free R-SH group at Cys51 is not responsible for the inhibition. FSH-beta 33-53 also significantly stimulated basal levels of estradiol synthesis, but not to maximal levels observed with FSH (partial agonist). Neither the carbohydrate content of hFSH-beta nor the alpha subunit of FSH appears to be essential for signal transduction and expression of the hormone effect of FSH-beta 33-53.

Cell Membrane↗

PubMed1990

Pituitary luteinizing hormone (LH) and follicle-stimulating hormone (FSH) responses to gonadotropin-releasing hormone during the rat estrous cycle: an increased ratio of FSH to LH is secreted during the secondary FSH surge.

The hormonal interactions required for the generation of a secondary surge of FSH on the evening of proestrus have not been clearly defined. The role of GnRH in driving a surge of FSH has been questioned by findings in previous studies. In the current study, gonadotropin secretion was measured from pituitary fragments obtained from rats at 0900 and 2400 h on each day of the estrous cycle. Pituitary fragments were perifused in basal (unstimulated) conditions or in the presence of GnRH pulses to determine whether a selective increase in basal release of FSH and/or an increase in the responsiveness to GnRH occurs during the secondary FSH surge. Each anterior pituitary was cut into eighths and placed into a microchamber for perifusion. Seven pulses of GnRH (peak amplitude = 50 ng/ml; duration = approximately 2 min) were administered at a rate of one per hour starting at 30 min. Fractions of perfusate were collected every 5 min and frozen until RIA for LH and FSH. The mean total amount of LH or FSH secreted during the hour interval following each of the last six pulses of GnRH (or the corresponding basal hour) was calculated. Analysis of variance with repeated measures indicated that the evening secretion of LH on proestrus (2400 h) dropped significantly (p less than 0.05) from a maximum on the morning of proestrus (0900 h), whereas the FSH secretion remained elevated at this time. Therefore, the ratio of FSH to LH secreted in response to GnRH pulses was highest during the secondary FSH surge and lowest on the morning of proestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Direct actions of the luteinizing hormone-releasing hormone agonist, deslorelin, on anterior pituitary contents of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), LH and FSH subunit messenger ribonucleic acid, and plasma concentrations of LH and FSH in castrated male cattle.

The objective in this study was to characterize direct effects of the LHRH agonist, deslorelin, on anterior pituitary gland function in male cattle in the absence of gonadal feedback. Castrated bulls (steers), 30 mo old, were allocated to four groups: group 1, control, no treatment (n = 8); group 2, five deslorelin implants (approximately 250 micrograms total deslorelin/day) for 42 days (n = 8); group 3, control+ LHRH (50 micrograms i.m.) at weekly intervals (n = 3); group 4, five deslorelin implants+LHRH as for group 3 (n = 3). Plasma LH was similar (p > 0.05) for steers in groups 1 and 2 on Day 0 and lower (p < 0.05) for steers in group 2 on Day 4, and continued to decrease to Day 41 (group 1, 1.71 +/- 0.20 ng/ml [mean +/- SEM]; group 2, 0.38 +/- 0.03 ng/ml [p < 0.001]). Mean plasma concentrations of FSH were similar (p > 0.05) for steers in groups 1 and 2 on Day 0 and lower (p < 0.05) for steers in group 2 on Day 7, and declined to Day 41 (group 1, 43.5 +/- 3.9 ng/ml; group 2, 17.5 +/- 1.5 ng/ml [p < 0.001]). Steers in group 3 showed increases in plasma LH after injection of LHRH on all occasions, while steers in group 4 did not show increases in plasma LH from Day 14 onward. Mean relative pituitary contents (arbitrary units) of LH beta- and FSH beta-subunit mRNAs were reduced on Day 42 in steers treated with deslorelin (LH beta: groups 1 and 3, 1.56 +/- 0.27; groups 2 and 4, 0.08 +/- 0.01 [p < 0.001]; FSH beta: groups 1 and 3, 1.01 +/- 0.08; groups 2 and 4, 0.34 +/- 0.07 [p < 0.001]). However, alpha-subunit mRNA was similar for control steers and steers treated with deslorelin (groups 1 and 3, 1.00 +/- 0.11; groups 2 and 4, 0.86 +/- 0.12 [p > 0.1]). Pituitary content of LH, but not FSH, was reduced in steers treated with deslorelin. In summary, steers treated with deslorelin showed desensitization to natural LHRH, and this was associated with reduced pituitary contents of LH and FSH beta-subunit mRNAs, a reduction in pituitary content of LH, and decreases in plasma concentrations of LH and FSH. This demonstrated, for the first time, a direct action of LHRH agonist on LH and FSH beta-subunit gene expression in cattle, independent of gonadal feedback. Also, there was a differential effect of treatment with deslorelin on gonadotropin alpha- and beta-subunit mRNA contents in the anterior pituitary.

Animals↗

PubMed2001

Follicle-stimulating hormone (FSH) induced internalization of porcine FSH receptor in cultured porcine granulosa cells and Chinese hamster ovary cells transfected with recombinant porcine FSH receptor cDNA.

In order to study the fate of human follicle-stimulating hormone (FSH) when hormone binds to its receptor, a quick biochemical method that can differentiate between the surface-bound and internalized hormone was used to determine the internalization induced by FSH in cultured both porcine granulosa cells and Chinese hamster ovary (CHO) cells expressing recombinant porcine FSH receptor. The results showed that FSH was slowly internalized, and the internalized radioactivity (acid resistant) reached a peak 10-12 h after addition of 125I-hFSH. It was suggested that FSHR do not get internalized rapidly under physiological circumstances precisely because the appropriate sequences are absent.

Animals↗

PubMed2004

Estimation of the follicle-stimulating hormone (FSH) threshold for initiating the final stages of follicular development in women with elevated FSH levels in the early follicular phase.

OBJECTIVE: To test the hypothesis that the follicle-stimulating hormone (FSH) threshold in patients with elevated FSH levels in the early follicular phase (EFP) is higher than in controls. DESIGN: Pilot study. SETTING: Academic hospital. PATIENT(S): Six patients with elevated EFP FSH (>10 IU/L) and 13 controls. INTERVENTION(S): Treatment with a GnRH agonist in the midluteal phase before IV administration of recombinant FSH was started in an ultra-low-dose step-up protocol. The FSH threshold was determined by the mean of FSH levels of the above threshold value and the below threshold value. MAIN OUTCOME MEASURE(S): Follicle-stimulating hormone threshold, FSH screening value, E(2), number of follicles. RESULT(S): The FSH threshold in the elevated EFP FSH group was 6.75 IU/L and was significantly higher than the FSH threshold of the controls (4.65 IU/L). The FSH screening value on day 3 was 12.0 IU/L in the patient group and 5.0 IU/L in the controls. Estradiol was significantly lower on the day that the largest follicle was 18 mm in the elevated EFP FSH group compared with controls (277 vs. 491 pmol/L, respectively). On the day of hCG administration, the number of smaller (10-13 mm) follicles was equal but the number of larger (>14 mm) follicles was higher in the control group compared with the elevated FSH group. In the control group, the basal FSH levels correlated highly with the FSH threshold levels (r = 0.8), but in the patients with elevated EFP FSH this correlation was absent. CONCLUSION(S): In normal women, basal FSH day 3 values represent the ovarian threshold for FSH. In women with elevated day 3 FSH, the FSH threshold is higher but not as high as basal FSH values. We postulate that the FSH threshold in patients with elevated EFP FSH is higher because of intraovarian factors. Basal FSH overshoots the threshold, probably because of the limited feedback by the ovary.

Chorionic Gonadotropin↗

PubMed1997

Primary gonadal failure in men selectively amplifies the mass of follicle stimulating hormone (FSH) secreted per burst and increases the disorderliness of FSH release patterns: reversibility with testosterone replacement.

The neuroendocrine mechanisms by which primary gonadal failure in men increases mean serum FSH concentrations (castration-like response) are not known. To investigate the testosterone-dependent mechanisms of the FSH castration response: (i) blood was sampled at 10-min intervals for 24 h for later FSH assay in seven normal middle-aged men and in six patients with primary testicular failure, during testosterone withdrawal and after 6 weeks of parenteral testosterone replacement; (ii) using a specific two-site IRMA, serum FSH concentrations were measured, since this assay correlates well with an in-vitro Sertoli cell bioassay; (iii) multiparameter deconvolution analysis was then applied to estimate the frequency, amplitude, duration, and mass of underlying FSH secretory bursts, and the half-life of endogenous FSH, and (iv) approximate entropy was calculated to quantify the relative orderliness of FSH release over 24 h. Mean (+/- SEM) 24-h serum FSH concentrations were 3.9 +/- 0.8 IU/L in control subjects and 39 +/- 10 IU/L in unreplaced hypogonadal patients (p = 0.034). Deconvolution analysis revealed similar estimated mean FSH half-lives of 346 +/- 40 min (control) and 321 +/- 47 min (untreated patients), and indistinguishable FSH secretory burst frequencies, namely, 20 +/- 0.95 (normal) and 21 +/- 1.3 (patients) pulses per 24 h. In contrast, the daily production rate of FSH was markedly increased in testosterone-withdrawn hypogonadal men at 117 +/- 25 vs. 9.3 +/- 1.8 IU/L/day (control) (p < 0.01). This was due to a 10-fold higher calculated maximal rate (amplitude) of FSH secretion achieved within each FSH release episode (normal 0.078 +/- 0.02 vs. gonadal failure 0.74 +/- 0.087 IU/L/min, p < 0.01), yielding a 10-fold increase in the mass of FSH secreted per burst (control 0.53 +/- 0.06 vs. patients 5.3 +/- 0.81 IU/L, p < 0.01). In contrast, the mean half-duration of FSH secretory bursts was unaltered in unreplaced hypogonadal men at 8.2 +/- 2.2 min (control) vs. 7.0 +/- 1.0 min (patients). Approximate entropy (ApEn), a scale- and model-independent statistic designed to quantify the orderliness or regularity of hormone release, revealed greater irregularity of serum FSH concentrations in the hypoandrogenic state: ApEn = 1.8 +/- 0.025 (testosterone-withdrawn) vs. 1.6 +/- 0.037 (control) (p < 0.05). Parenteral testosterone replacement for 6 weeks significantly decreased mean serum FSH concentrations by reducing the daily FSH secretion rate and FSH secretory burst amplitude and mass, and concomitantly restored the orderliness of FSH release patterns. Testosterone treatment did not change FSH secretory burst half-duration, number, interburst interval, or half-life. It is concluded that primary gonadal failure in men evokes FSH hypersecretion which is marked by more disorderly FSH release patterns and a selectively amplified mass of FSH secreted per burst. These hypergonadotrophic mechanisms are, to a significant extent, testosterone-suppressible.

Follicle Stimulating Hormone↗

PubMed1994

Clinical pharmacology of recombinant human follicle-stimulating hormone (FSH). I. Comparative pharmacokinetics with urinary human FSH.

OBJECTIVE: To assess and compare the pharmacokinetics of recombinant human FSH with those of a reference preparation of urinary human FSH. DESIGN: Urinary human FSH and recombinant human FSH (Metrodin and Gonal-F; Laboratoires Serono, Aubonne, Switzerland) were administered in a balanced, random order, crossover sequence as a single i.v. dose of 150 or 300 IU separated by 1 week of washout to 12 pituitary down-regulated, healthy female volunteers. Serum FSH concentrations were measured by an immunoradiometric assay (IRMA) and by an in vitro rat granulosa cell aromatase bioassay. Urine FSH concentrations were measured by IRMA. RESULTS: The mean concentration-time profiles after 150 IU of urinary human FSH and recombinant human FSH were superimposed, and the mean profile after 300 IU of recombinant human FSH was double that of the 150 IU dose. The data for both FSH preparations were well described by a biexponential equation. Total clearance of the preparations was comparable, judging from immunoassay and bioassay data (0.5 and 0.15 L/h, respectively). Based on the immunoassay, renal clearance of urinary human FSH was 0.1 L/h, whereas for recombinant human FSH it was slightly lower at 0.07 L/h, indicating that less than one fifth of the administered dose was excreted in the urine. Immunoassay showed that the two preparations were similar in terms of initial and terminal half-lives (2 and 17 hours, respectively). The volumes of distribution at steady state (11 L) were similar. The results of the in vitro bioassay confirmed this pharmacokinetic analysis. Just after i.v. administration, an initial decrease in the serum bioassay:immunoassay ratio was observed because of dilution of urinary human FSH or of recombinant human FSH in the residual endogenous FSH pool. Then the ratio increased progressively with time, suggesting either metabolic selection or activation of both types of injected human FSH toward forms with greater in vitro bioactivity. The bioassay:immunoassay ratio returned to baseline by day 7. CONCLUSION: The results obtained in this study indicate that the following [1] the pharmacokinetic characteristics of recombinant human FSH are similar to those of urinary human FSH; [2] the terminal half-life of human FSH is approximately 1 day; [3] after a single i.v. injection of human FSH a progressive increase in FSH bioassay: immunoassay ratio is observed; and [4] clinical use of recombinant human FSH could follow protocols and treatment regimens currently applied to urinary human FSH.

Adult↗

PubMed1993

Pulsatile administration of gonadotropin-releasing hormone does not alter the follicle-stimulating hormone (FSH) isoform distribution pattern of pituitary or circulating FSH in nutritionally growth-restricted ovariectomized lambs.

The experimental induction of puberty by GnRH administration to prepubertal lambs increases serum bioactive FSH (B-FSH) as measured in the rat Sertoli cell aromatase induction bioassay. Serum immunoreactive FSH (I-FSH) levels are unchanged. The increase in serum B-FSH is associated with an increase in the proportion of less acidic and more biopotent FSH serum isoforms. However, it is unknown if this effect of GnRH on serum FSH microheterogeneity is direct or mediated by gonadal factors. We have used the nutritionally growth-restricted ovariectomized lamb as a model of the neuroendocrine regulation of FSH isoform microheterogeneity. With this model, the hypothalamic-pituitary component of the neuroendocrine axis may be isolated from gonadal factors. In the present study, using the nutritionally growth-restricted ovariectomized lamb as a model, we investigated the role of GnRH on the regulation of FSH microheterogeneity. Specifically, we tested the hypothesis that GnRH increases the proportion of the less acidic (more biopotent) serum FSH isoforms. As an in vitro correlate, we investigated the effect of GnRH on gonadotropin secretion and FSH isoform distribution in ovine pituitary explant cultures. Seven ovariectomized nutritionally restricted lambs were administered GnRH (i.v., 2 ng/kg) for 36 h (at 2-h intervals for 24 h, then hourly for the final 12 h). Six others served as controls. Blood samples were withdrawn at 12-min intervals during the last 4 h for the measurement of serum immunoactive LH (I-LH) and I-FSH. Pituitary homogenates and serum from four animals from each group were individually chromatofocused, and the FSH isoform distribution patterns were determined. Pulsatile administration of GnRH to nutritionally growth-restricted lambs increased circulating I-LH concentrations from 0.6 +/- 1.0 to 5.9 +/- 3.1 ng/ml (P < 0.01), but did not significantly change circulating I-FSH (4.9 +/- 1.8 vs. 11.5 +/- 4.2 ng/ml) nor B-FSH concentrations (3.9 +/- 1.2 vs. 5.7 +/- 1.5 ng/ml). The pituitary content of I-FSH, B-FSH, and I-LH were unchanged. Neither serum nor pituitary FSH isoform distribution patterns were altered by pulsatile GnRH administration. However, compared to the pituitary FSH isoforms, a higher percentage of circulating FSH isoforms eluted in the salt peak of both groups of lambs. Similar to the in vivo studies, in vitro, GnRH increased the release of I-LH, as well as I-FSH, from pituitary explants, but did not significantly change the FSH isoform distribution in either the pituitary explant or media.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Nutritional Physiological Phenomena↗

PubMed1996

Homologous in vitro bioassay for follicle-stimulating hormone (FSH) reveals increased FSH biological signal during the mid- to late luteal phase of the human menstrual cycle.

Monitoring of the secretory dynamics of FSH during the human menstrual cycle has demonstrated conflicting results between the amounts of FSH measured by dimer-specific immunoassays and previous heterologous in vitro bioassays. These differences suggest somewhat different models of the steroidal and nonsteroidal regulation of FSH secretion and its control of folliculogenesis in the human. We have developed a homologous in vitro bioassay, using the recombinant human FSH receptor cotransfected into Chinese hamster ovary cells with a cAMP-responsive luciferase reporter gene, that overcomes many of the theoretic shortfalls of previous assays and allows reevaluation of the changes in bioactive FSH across the menstrual cycle. Bioactive FSH levels measured across 12 menstrual cycles in 11 normal women ranged from 4-40 IU/L. FSH bioactivity was constant during the menstrual cycle, with elevations noted only during the mid- to late luteal phase. Bioactive FSH levels were similar to immunoactive FSH levels across the cycle as indicated by a ratio of bioactive to immunoreactive FSH (FSH B/I) of 1.10 +/- 0.04 across the follicular and early luteal phases. However, during the mid- to late luteal phase, the mean FSH B/I rose to 1.65 +/- 0.07, which significantly exceeded that during the rest of the cycle (P < 0.001). This change in FSH B/I occurs at a critical time during folliculogenesis when the next cohort of follicles is being recruited and appears to be secondary to a decrease in immunoreactive FSH unaccompanied by a similar decrease in in vitro bioactivity. There was good agreement between immunoassay and bioassay results on the day of the midcycle gonadotropin surge (FSH B/I = 1.07 +/- 0.14), which was not different from that in the follicular phase (days -17 to -2; FSH B/I = 1.06 +/- 0.05) or the FSH B/I measured in postmenopausal women (0.93 +/- 0.2). These observations using a novel homologous human FSH in vitro bioassay indicate that bioactive FSH levels are not declining during the time of active corpus luteum formation and secretory activity. Thus, there is a previously undetected increased biologic signal during the mid- to late luteal phase, suggesting that the influence of elevated FSH on the cohort of developing follicles (including the subsequent dominant follicle) begins earlier during the luteal-follicular transition than previously predicted by FSH immunoreactivity.

Adult↗

PubMed1988

Autoregulation of acute progesterone and adenosine 3',5'-monophosphate responses to follicle-stimulating hormone (FSH) in porcine granulosa cells: effects of FSH, cholera toxin, forskolin, and pertussis toxin.

The purpose of these studies was to determine how exposure to FSH affects subsequent responsiveness of adenylyl cyclase and progesterone production to FSH in immature porcine granulosa cells in vitro. Acute cAMP and progesterone responses to FSH and the postreceptor activators of cyclase, forskolin and cholera toxin, were determined after a 24-h preincubation with FSH. Pretreatment with FSH (1-1000 ng/ml) resulted in an increase in subsequent basal progesterone production which was dependent on preincubation FSH concentration. The cAMP response to FSH, on the other hand, was reduced after preincubation with FSH in a manner dependent on preincubation FSH concentration. Removal of FSH with acidified medium and subsequent incubation in FSH-free medium resulted in recovery of the cAMP response to FSH, indicating that attenuation of the response is reversible. Attenuation of the cAMP response to FSH does not appear to be due to 1) a loss of activity of the catalytic moiety of cyclase, since the response to forskolin and cholera toxin was not decreased by FSH; 2) a decrease in coupling of the stimulatory guanine nucleotide regulatory protein with the catalytic moiety of cyclase, since the response to cholera toxin was not reduced by FSH; 3) inhibitory signals, since preincubation with pertussis toxin did not affect the subsequent response to FSH; or 4) cAMP itself, since neither cholera toxin nor the cAMP analog 8-(4-chlorophenyl-thio)cAMP affected the response to FSH. It appears, instead, that FSH regulates FSH responsiveness by regulating the interaction of the FSH receptor with stimulatory guanine nucleotide regulatory protein.

Adenylate Cyclase Toxin↗

PubMed2006

Follicle-stimulating hormone (FSH) activates extracellular signal-regulated kinase phosphorylation independently of beta-arrestin- and dynamin-mediated FSH receptor internalization.

BACKGROUND: The follicle-stimulating hormone receptor (FSH-R) is a seven transmembrane spanning receptor (7TMR) which plays a crucial role in male and female reproduction. Upon FSH stimulation, the FSH-R activates the extracellular signal-regulated kinases (ERK). However, the mechanisms whereby the agonist-stimulated FSH-R activates ERK are poorly understood. In order to activate ERK, some 7 TMRs require beta-arrestin-and dynamin-dependent internalization to occur, whereas some others do not. In the present study, we examined the ability of the FSH-activated FSH-R to induce ERK phosphorylation, in conditions where its beta-arrestin- and dynamin-mediated internalization was impaired. METHODS: Human embryonic kidney (HEK) 293 cells were transiently transfected with the rat FSH-R. Internalization of the FSH-R was manipulated by co-expression of either a beta-arrestin (319-418) dominant negative peptide, either an inactive dynamin K44A mutant or of wild-type beta-arrestin 1 or 2. The outcomes on the FSH-R internalization were assayed by measuring 125I-FSH binding at the cell surface when compared to internalized 125I-FSH binding. The resulting ERK phosphorylation level was visualized by Western blot analysis. RESULTS: In HEK 293 cells, FSH stimulated ERK phosphorylation in a dose-dependent manner. Co-transfection of the beta- arrestin (319-418) construct, or of the dynamin K44A mutant reduced FSH-R internalization in response to FSH, without affecting ERK phosphorylation. Likewise, overexpression of wild-type beta-arrestin 1 or 2 significantly increased the FSH-R internalization level in response to FSH, without altering FSH-induced ERK phosphorylation. CONCLUSION: From these results, we conclude that the FSH-R does not require beta-arrestin- nor dynamin-mediated internalization to initiate ERK phosphorylation in response to FSH.

Animals↗