Elevated ovarian expression and serum concentration of alpha inhibin in the luteal phase during follicular development in the squirrel monkey (Saimiri boliviensis) compared to the human

The goal of the present investigation was to determine in the squirrel monkey the source and pattern of inhibin, a hormone known to effect reproductive steroid levels via pituitary and ovarian mechanisms. Since this seasonally polyestrous species is known to have elevated serum levels of reproductive steroids compared to other primates, the levels of ovarian alpha subunit mRNA expression and serum total alpha inhibin, estradiol, progesterone, and luteinizing hormone were measured and compared to human levels. Expression of the alpha subunit was robust in monkey luteal tissue compared to expression in human luteal tissue. Squirrel monkey serum inhibin peaked 4 days after the luteinizing hormone surge and correlated with progesterone changes. These luteal serum levels of inhibin were greater than 12 times higher than the human levels yet bio-LH activities were less than in the human during the luteal phase. Inhibin concentrations during the nonbreeding season were generally half the levels measured in the breeding season and undetectable in ovariectomized animals. However, exogenous FSH stimulation induced a marked rise in inhibin, which correlated with an estradiol rise. In conclusion, abundant alpha inhibin subunit expression in the luteal ovary of the squirrel monkey and loss of serum delectability in ovariectomized animals indicates that the principle source of inhibin in the squirrel monkey is the ovary. Elevated serum inhibin levels during the luteal phase concurrent with ovulatory-size follicular development is unique among species studied thus far. Possible simultaneous inhibin production from both follicular and luteal tissue may be responsible for the exceptionally high inhibin levels.

Immunoreactive and bioactive LH release from pituitaries of intact or castrated male rats: effect of in vitro GnRH and KCl administration

The in vitro immunoreactive (i-LH) and bioactive (b-LH) LH release from hemipituitaries of intact adult male rats (INT) or rats castrated 7 days earlier (CAS) was studied. Hemipituitaries were incubated for 30 min (time 1) plus an additional 30 min (time 2) with GnRH (10 nM) and/or KCl (50 mM), according to one of the following protocols: media alone (C), KCl+KCl (K/K), GnRH+GnRH (G/G), KCl+GnRH (K/G), GnRH+KCl (G/K). All of the hemipituitaries were further incubated in media alone for 120 min (time 3). I-LH, b-LH and i-FSH were assayed on the media. In both models, the highest bioactive:immunoactive (b/i) ratio was noted during time 1; however, CAS always secreted more b-LH than INT at any given time of the study. In INT, GnRH--but not KCl--administration during time 2 resulted in blunted i-LH. During the same time, the b/i ratios decreased in all groups but G/K. LH secretion recovered during time 3 in all groups. In CAS, i-LH levels comparable to those of time 1 were sustained by either stimulus during time 2, while the b/i ratios were markedly decreased. LH secretion recovered in the K/K group during time 3. These results suggest that: 1) promptly releasable pools of b-LH are available in both models; 2) CAS always secrete more b-LH; 3) in INT, desensitization occurs involving parallel changes in both i-LH and b-LH, while changes in b-LH rather than i-LH are noted in CAS; 4) prolonged KCl administration might play a role in new gonadotropin synthesis and/or release.

Recombinant human inhibin-A administered early in the menstrual cycle alters concurrent pituitary and follicular, plus subsequent luteal, function in rhesus monkeys

Inhibin, a suppressor of pituitary FSH secretion in nonprimate species, may also act in the ovary to regulate follicular development. To examine whether inhibin has similar actions in primates, female rhesus monkeys (n = 3/treatment), exhibiting regular menstrual cycles, received sc injections of either vehicle or 60 micrograms/kg recombinant human inhibin-A at 0800 and 1600 h for 5 days beginning at menses. The vehicle-treated monkeys displayed menstrual cycles of normal length, with the follicular (11.3 +/- 2.5 days, mean +/- SE) and luteal (16.3 +/- 2.5 days) phases demarcated by midcycle peaks in serum estradiol (E) and bioactive LH. After the first inhibin injection, levels of immunoreactive inhibin A peaked at 10 ng/mL within 1 h and returned to baseline (< 0.1 ng/mL) before the second injection 8 h later. Although serum E and LH did not change, bioactive FSH decreased (to 66% of pretreatment levels, P < 0.05) within 8 h. Within 1 day, circulating bioactive FSH was less (P < 0.05) in inhibin-treated monkeys, compared with controls. By 2-3 days, serum E levels were also markedly (P < 0.05) reduced in inhibin-treated animals, whereas bioactive LH rose 3-fold (P < 0.05). After inhibin treatment, the midcycle rises in serum E and LH were delayed; hence, the follicular phase was prolonged (15.0 +/- 2.6 days, P < 0.05), compared with controls. Although the patterns and levels of serum LH circulating during the subsequent luteal phase seemed comparable in both groups, mean progesterone levels were suppressed to 2-3 ng/mL (P < 0.05) during the midluteal phase in inhibin-treated monkeys. However, the length of the luteal phase in inhibin-treated cycles (13.0 +/- 2.6 days) was not significantly altered. We conclude that exogenous inhibin rapidly diminishes pituitary FSH secretion in female monkeys during the early follicular phase of the menstrual cycle. This action, and/or other actions directly on the ovary, leads to subsequent effects on follicular steroidogenesis and pituitary LH secretion that culminate in an aberrant ovarian cycle characterized by an insufficient luteal phase. The study identifies, for the first time, possible activities and roles of inhibin during the ovarian cycle in primates.

Circulating immunoreactive and bioactive follicle stimulating hormone concentrations in anovulatory infertile women and during gonadotrophin induction of ovulation using a decremental dose regimen

Our purpose was to determine whether decreased follicle stimulating hormone (FSH) activity, either systemic or at the follicular level, is involved in impaired follicle growth associated with normogonadotrophic anovulation. To differentiate between the possible levels of disturbance, bioactive (BIO-FSH; using the in-vitro rat granulosa cell aromatase bioassay) and immunoreactive (IRMA-FSH) FSH serum concentrations of three groups of subjects were compared: (i) 172 normogonadotrophic anovulatory infertile women during baseline conditions, (ii) 22 clomiphene-resistant polycystic ovary syndrome patients undergoing ovulation induction by exogenous gonadotrophins using a decremental dose regimen, and (iii) nine regularly cycling controls. BIO-FSH [13.2 (range 0.8-29.5) IU/l] and IRMA-FSH [4.4 (range 1.2-9.3) IU/l] concentrations in anovulatory women during baseline conditions were significantly lower than maximum concentrations reached during the follicular phase in controls [18.7 (13.2-23.4) and 6.4 (5.7-10.0) IU/l respectively], but were not significantly different from initial concentrations in controls [10.4 (7.2-19.6) and 4.8 (2.8-8.2) IU/l respectively]. Moreover, concentrations of IRMA-FSH and BIO-FSH were negatively correlated (r = -0.25, P = 0.01, and r = -0.24, P = 0.02 respectively) with the interval between last vaginal bleeding and blood sampling. Maximum concentrations of IRMA-FSH [7.6 (3.9-10.9) IU/l] during ovulation induction by gonadotrophins were not significantly different from maximum [6.4 (5.7-10.0) IU/l] concentrations in controls, whereas maximum BIO-FSH concentrations [13.5 (8.7-17.4) versus 18.7 (13.2-23.4) IU/l] were significantly lower. Our findings suggest that (i) circulating FSH does not reach concentrations that are sufficient to induce normal follicle development in anovulatory women during baseline conditions, and (ii) the FSH threshold for ovarian stimulation of this patient group is not different from normal.

A technique for sorting rat gonadotropes using anti-LH or anti-FSH antibodies covalently attached to magnetic beads

A technique for sorting live LH- and FSH-secreting cells was developed. After enzymatic dispersion, a suspension of pituitary cells from male rats castrated 7 days earlier was incubated in potassium chloride (KCI 50 mmol/l) for 30 min and gonadotropin outflow was provoked. Then, considering either LH or FSH as temporary surface markers, we positively selected the secreting cells by means of antibodies toward either LH (anti-LH beads) or FSH (anti-FSH beads) covalently attached to magnetic beads. The spontaneous secretion of LH and FSH overnight and the release induced by KCI the following morning were calculated. A population enriched in gonadotropes (16% of the total) able to secrete both gonadotropins was selected by means of anti-LH beads; this released 7 times as much LH as non-selected cells. A similar population (14% of the total) was selected by means of anti-FSH-coated beads; this produced 3.3 times as much LH as non-selected cells. In some experiments, the cells not previously sorted with anti-LH-coated beads were further incubated in the presence of anti-FSH beads, in an attempt to isolate a population secreting only FSH. A limited number of cells were sorted (6% of the total cells), able to produce both gonadotropins, but with a lower LH/FSH ratio. Similarly, those cells excluded by the selection with anti-FSH beads were further incubated with anti-LH beads, with a view to obtaining only-LH-secreting cells. However, both gonadotropins were still secreted by these cells (8% of the total), which had the highest LH/FSH ratio. In conclusion, fractions from castrated male rats that are enriched in gonadotropes contain cells that secrete both gonadotropins in vitro. The secretion of LH is prevalent. However, differences in the LH/FSH ratio between the populations sorted and changes from spontaneous to stimulated release are observed. This suggests that some gonadotropes might 'specialize' in releasing LH and others in releasing both LH and FSH.

Delayed puberty in males with beta-thalassemia major: pulsatile gonadotropin-releasing hormone administration induces changes in gonadotropin isoform profiles and an increase in sex steroids

Patients with beta-thalassemia major often have pubertal delay, the etiology of which has not been fully elucidated. We investigated the pituitary-gonadal response to short-term subcutaneous pulsatile gonadotropin-releasing hormone (GnRH) administration (150 ng/kg body weight every 120 min for 7 days) in five young males (aged 13.6-19.0 years) affected by beta-thalassemia major and presenting signs of delayed puberty. Immunoreactive and bioactive gonadotropin levels were determined and their isoform profiles were examined, before and after GnRH treatment, in a pool of samples collected every 15 min for 240 min. Testosterone, androstenedione, 17-hydroxyprogesterone, dehydroepiandrosterone and 17 beta-estradiol were measured as markers of gonadal function on days 0, 1, 3, 5 and 7 of treatment. Five patients (aged 16.9-26.8 years) with confirmed diagnosis of idiopathic hypogonadotropic hypogonadism who were starting pulsatile GnRH therapy were also studied in the same protocol. Increased sex steroid levels were observed in both groups as a result of treatment. On day 7, the thalassemic patients had increased bioactive luteinizing hormone (LH) and follide-stimulating hormone (FSH), although immunoreactive LH and FSH were comparable to day 0. Moreover, fewer acidic and more basic immunoreactive and bioactive isoforms were noted in LH profiles on day 7. Similar results were observed in hypogonadal patients, who also had increased immunoreactive LH and FSH values. We suggest that the early stage of delayed puberty in thalassemia might be characterized by a neuroendocrine dysfunction resulting in an impaired hypothalamic GnRH release, which is inadequate for a proper pituitary stimulation. Pulsatile GnRH treatment seems to re-establish partially the correct pituitary-gonadal function.

Gonadotropin requirements of the developing follicle

OBJECTIVE

To evaluate follicular FSH and LH requirements during suppression of endogenous gonadotropins with the GnRH antagonist Nal-Glu and whether LH-like activity could be supplied by administering subcutaneous hCG.

DESIGN

Randomized clinical trial.

PARTICIPANTS

Thirty-two normally cycling females in the late follicular phase (dominant follicle mean diameter > or = 14 mm).

INTERVENTION

Twelve normal women were randomized to receive 150 IU IM FSH with or without 75 IU SC hCG; 11 subjects were randomized to receive 225 IU FSH with or without 50 IU SC hCG; 9 women received 150 or 225 IU IM hMG. Subjects returned the next day for repeat blood sample and ultrasound.

RESULTS

Continued follicular maturation, as evidenced by rising E2 levels, correlated with serum immunoactive and bioactive FSH levels and was unrelated to bioactive LH-hCG. Two hundred twenty-five international units of exogenous FSH consistently supported follicular maturation. There was a similar increase in mean follicular diameter in women with an E2 rise versus those with a plateau or fall. In subjects receiving SC mini-dose hCG, serum bioactive LH-hCG levels were increased significantly and were similar to levels before Nal-Glu.

CONCLUSIONS

During administration of a GnRH-a, the maturing follicle appears to require only FSH support. In markedly hypogonadotropic women, mini-dose hCG may be a more practical alternative to recombinant LH to promote normal follicle maturation.

Effects of corticosterone and testosterone on pituitary gonadotropin content, secretion, bioactivity and messenger RNA levels in the presence or absence of GnRH in male rats

The effects of corticosterone (B) and testosterone (T) on pituitary and serum bioactive and immunoreactive gonadotropins and on gonadotropin hormone subunit messenger RNA levels were compared in the absence of GnRH. Male rats were implanted with pellets of either cholesterol, B or T. At implantation, 2 and 4 days later half of each group received GnRH antagonist and animals were killed 5 days after implantation. As expected, GnRH antagonist lowered bioactive and immunoreactive serum FSH and LH, pituitary FSH, LHβ and FSHβ mRNA. B treatment alone lowered bioactive and immunoreactive serum FSH and immunoreactive serum LH. B reversed the antagonist effect on bioactive and immunoreactive pituitary FSH and FSHβ mRNA. T alone lowered bioactive and immunoreactive serum FSH and LH levels. T reversed the antagonist effect on bioactive and immunoreactive pituitary FSH. T lowered bioactive and immunoreactive pituitary LH and LHβ mRNA and partially reversed the antagonist effect on FSHβ mRNA. The data suggest that either B or T enhance FSH synthesis by acting directly at the gonadotrope, but that B does not affect LH variables to the same extent as T. The results suggest that in stressed animals, when T levels are reduced, B can substitute for T in sustaining FSH synthesis.

Systemic and intraluteal infusion of inhibin A or activin A in rhesus monkeys during the luteal phase of the menstrual cycle

The endocrine or local actions of inhibin-related peptides synthesized by the primate corpus luteum (CL) remain undefined. This in vivo study was designed to determine whether exogenous inhibin or activin modulates pituitary gonadotropin secretion and the functional life span of the CL during the luteal phase of the menstrual cycle. Beginning at midluteal phase of the cycle, either vehicle or 1 microgram/h of recombinant human inhibin A or activin A (n = 3-6 per treatment group) was infused into rhesus monkeys via the jugular vein (i.e., peripheral infusion) or directly into the CL (i.e., intraluteal infusion) by means of an osmotic minipump for 7-14 days. Daily samples of saphenous venous serum were assayed for estradiol (E) and progesterone (P) content by RIA, and for FSH and LH levels by bioassay. Intraluteal infusion of inhibin or activin did not alter circulating P levels or the length of the luteal phase compared to those values in vehicle-infused controls. Likewise, LH levels were not different between the three groups. However, FSH levels declined progressively during inhibin infusion to 26% of pretreatment levels (p < 0.05), whereas FSH levels in vehicle-infused controls were unchanged for several days and then rose (p < 0.05) to peak levels around menses. FSH levels did not change significantly during activin infusion into the CL. Although similar results were obtained in monkeys receiving peripheral or intraluteal infusions of inhibin, events following the peripheral infusion of activin were markedly different from those during intraluteal administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Follistatin decreases activin-stimulated FSH secretion with no effect on GnRH-stimulated FSH secretion in prepubertal male monkeys

Follistatin is an activin-binding glycoprotein that decreases FSH secretion in vitro and in vivo in rats. The mechanism by which follistatin acts is unclear, but it has been suggested that it may bind endogenous activin and neutralize its effects. In this study, we wished to test the ability of follistatin to suppress FSH secretion in vivo in primates whose FSH secretion has been stimulated by activin or by GnRH. Six prepubertal male monkeys were injected intravenously with human recombinant follistatin at the dose of 90 micrograms/kg or 180 micrograms/kg plus activin (90 micrograms/kg) or GnRH (10 micrograms/kg). Frequent blood samples were drawn for 12 hours following each injection. Bio FSH and LH levels were measured in those samples. GnRH and activin each stimulated FSH bioactivity. Both doses of follistatin significantly inhibited the activin-induced increase in FSH (p < 0.05). The GnRH-induced increase in FSH was not affected by follistatin. LH levels were not affected by follistatin in any of the studies. These data suggest that follistatin can suppress the activin-induced increase in FSH in primates and is consistent with the hypothesis that follistatin can block the physiological effects of endogenous activin in primates. This effect is likely to be due to the binding of follistatin to activin either in the peripheral circulation or at the pituitary level.

The direct pituitary effect of testosterone to inhibit gonadotropin secretion in men is partially mediated by aromatization to estradiol

In men, administration of exogenous testosterone (T) exerts direct negative feedback effects at the pituitary as well as at the hypothalamic level. This study was undertaken to determine whether T itself causes the inhibitory effects on the pituitary, or whether conversion to estradiol (E2) or dihydrotestosterone (DHT) is required. We assessed the biological activity of serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as immunoactivity. Blood samples were drawn before, during, and after a continuous, 72-hour i.v. infusion of T (15 mg/day), E2 (90 micrograms/day), or DHT (500 micrograms/day). Each of these doses is twice the daily production rate of the steroid. Each man received each of the three steroid infusions. We studied four men, ages 23-35, with idiopathic hypothalamic hypogonadism (IHH), who were treated with pulsatile gonadotropin releasing hormone (GnRH) until their gonadotropins reached the normal range. Serum levels of T, E2, DHT, and levels of immunologically active and biologically active LH and FSH were measured. We found that administration of each steroid increased serum levels of the infused steroid to the upper physiologic range. Administration of T or E2 resulted in decreased mean levels of biologically and immunologically active LH and FSH; administration of DHT did not alter gonadotropin secretion. These data suggest that some of the direct effect of T at the pituitary level in men is mediated by E2, whereas peripherally formed DHT may not play an important role in this process.

Corticosterone in vivo increases pituitary follicle-stimulating hormone (FSH)-beta messenger ribonucleic acid content and serum FSH bioactivity selectively in female rats

Experimental objectives were to determine: 1) if the native glucocorticoid, corticosterone (B), can selectively increase pituitary FSH and FSH beta messenger RNA (mRNA) in the presence or absence of a GnRH signal; and 2) if B affects the biological activity of the gonadotropins. Metestrous female rats were implanted with cholesterol or B. Each implant group received 100 micrograms GnRH antagonist or control injections every 48 h beginning at the time of implantation, and were killed 5 days later. B significantly increased bioactive serum FSH, with or without GnRH antagonist. GnRH antagonist decreased bioactive serum FSH. Immunoreactive serum FSH was not affected by any treatment. B did not affect bioactive serum LH, but GnRH antagonist significantly suppressed bioactive serum LH. Immunoreactive serum LH was significantly lowered by either B or GnRH antagonist. Neither bioactive nor immunoreactive pituitary FSH or LH content were affected by B, GnRH antagonist, or combined treatments, and no treatment affected alpha or LH beta mRNA. B significantly increased FSH beta mRNA specifically, in the presence or absence of GnRH antagonist. These results demonstrate that corticosterone can increase biological activity of secreted FSH and increase FSH beta mRNA in the absence of a GnRH signal, suggesting a direct effect on the anterior pituitary gland.

Development of a human granulosa cell culture model with follicle stimulating hormone responsiveness

In order to study the effects of follicle-stimulating hormone (FSH) on differentiation of granulosa cells, a well-defined and validated in-vitro culture system is indispensable. In this study, pooled follicular aspirates were stimulated in vitro with FSH and luteinizing hormone (LH) for 2, 4 and 6 days, either immediately after plating or after 7 days of preincubation. Cultures were assayed for progesterone and oestradiol production. Fresh cells displayed very high basal progesterone production which could be stimulated with LH but not FSH. After preincubation, addition of LH and FSH resulted in dose-dependent increases of progesterone and oestradiol. When cultured on human fibronectin-coated wells, similar basal but higher progesterone concentrations after stimulation were observed. In comparison with serum-free media, addition of Serum-Plus resulted in higher basal and stimulated progesterone concentration, possibly due to the presence of serum factors. This study demonstrates firstly that after 7 days preincubation, cultures gained responsiveness to FSH but remained responsive to LH during 4 days of stimulation. This suggests a persisting differentiated cell population in vitro. Secondly, the use of human fibronectin extracellular matrix and serum promotes steroid production, either due to factors promoting cell growth and function or to availability of steroid precursors. Therefore one has to be cautious with interpretation of data obtained from this widely used culture system, employing highly differentiated cells obtained after ovarian stimulation for in-vitro fertilization for study of local regulation of granulosa cell function.

Human recombinant activin-A alters pituitary luteinizing hormone and follicle-stimulating hormone secretion, follicular development, and steroidogenesis, during the menstrual cycle in rhesus monkeys

Activin, a stimulator of pituitary FSH secretion in nonprimate species, may also act in the ovary to modulate follicular development. To examine whether activin has similar actions in primates, female rhesus monkeys (n = 3/treatment) exhibiting regular menstrual cycles received sc injections of either vehicle or 60 micrograms/kg recombinant human activin-A at 0800 and 1600 h for 1 (acute) or 7 (chronic) days beginning in the early follicular phase. The vehicle-treated monkeys displayed menstrual cycles of normal length, with the follicular (11.3 +/- 1.3 days, mean +/- SE) and luteal (16.6 +/- 1.8 days) phases demarcated by midcycle peaks in serum estradiol (E) and bioactive LH. After the first activin injection, levels of human activin A peaked at 90 ng/mL within 1 h and returned to baseline before the second injection 8 h later. Although serum E and FSH levels did not change, LH increased (273%, P < 0.05) within 8 h. Acute activin treatment increased (P < 0.05) serum E within 24 h to levels (1290 +/- 330 pmol/L) typically observed at midcycle. With chronic treatment, serum E peaked on day 2 (2580 +/- 338 pmol/L; P < 0.05), then declined and rose to a second peak (1680 +/- 279 pmol/L) on day 5. During chronic activin treatment, LH levels peaked on day 2 (603 +/- 270 ng/mL; P < 0.05 compared to day 0, 15 +/- 7 ng/mL) whereas FSH increased progressively until day 5 (937 +/- 320 ng/mL; P < 0.05 compared to day 0, 169 +/- 59 ng/mL). After acute or chronic activin, the expected midcycle rises in serum E and gonadotropins were delayed to greater than or equal to day 20 (n = 4) or did not occur before menses (n = 2). Although an enlarged ovary with one greater than or equal to 4-mm follicle was observed by laparoscopy during the late follicular phase in vehicle-treated monkeys, medium-to-large follicles were not visible on ovaries during chronic activin treatment or later at the expected midcycle interval in activin-treated monkeys. Similar hormonal and ovarian events were obtained after activin treatment of amenorrheic monkeys having serum FSH, LH, and E levels that were comparable to those at menses in spontaneous menstrual cycles. Thus, exogenous activin stimulates pituitary LH and FSH secretion and ovarian estrogen secretion during the early follicular phase in intact monkeys. However, acute or chronic activin treatment did not promote complete follicular development and disrupted subsequent events in the menstrual cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Validation of an improved in vitro bioassay to measure LH in diverse species

Cultured Leydig tumor cells (MA-10) respond to luteinizing hormone (LH) by synthesizing and secreting progesterone (P). The specificity of the response to LH prompted us to develop this system for use as a simple and rapid in vitro bioassay for LH. The aims of this study were to (1) improve sensitivity and reproducibility, and (2) optimize the assay for use in diverse animal species. A minimum sensitivity was observed at 0.05 mlU/well of LH with 0.5 x 10(4) cells/well for 1.5 hours. At higher concentrations of LH, shorter incubation periods also significantly stimulated P production. Addition of human LH standard or serum samples resulted in a dose-dependent increase in P production. Parallel dose-dependent curves were observed with LH preparations from mammalian, avian, and amphibian species. In conclusion, these findings demonstrate that (1) the assay is rapid, sensitive, and reproducible; (2) serum LH levels analyzed using this assay and the mouse Leydig cell bioassay are comparable; (3) shorter incubation times suggest the implementation of this assay for rapid qualitative determination of LH surges; and (4) the assay can be used for the analysis of samples from diverse species, especially those lacking radioimmunoassays. Therefore, this assay system allows for the simple and rapid measurement of circulating bioactive LH levels in humans and diverse animal species, and should provide insight regarding the role of bioactive LH in physiological and pathological conditions.

Apparent absence of negative feedback in middle-aged persistent-estrous rats following luteinizing hormone-releasing hormone agonist treatment: relation to plasma inhibin and 17 beta-estradiol

Reproductive aging in female rats is associated with a transition from regular estrous cyclicity to an anovulatory condition described as persistent estrous (PE). This PE condition is characterized by continued follicular development with elevated circulating levels of estrogen and FSH. In an attempt to investigate further the age-related changes in neuroendocrine function of PE rats, we have developed a model through which the return of hypothalamic-pituitary and ovarian function can be assessed following the withdrawal of chronic LHRH agonist suppression. Subsequent to withdrawal of continuous (2.5 micrograms/h for 12 days) LHRH agonist [DTrp6, Pro9-NHEt]-LHRH (LHRH-AG) treatment, circulating FSH concentrations in PE rats increase and remain elevated with an apparent absence of ovarian negative feedback, and these rats fail to return to estrous cyclicity. In the present studies, estrogen administration induced significant decreases in FSH secretion in PE rats following withdrawal of LHRH-AG treatment and ovariectomy (OVX), suggesting that the negative feedback response to estrogen is maintained in PE females. However, progesterone administration 2 days later failed to elicit a positive feedback response of gonadotropin secretion in PE females prior to LHRH-AG treatment, serum inhibin and 17 beta-estradiol (E2) concentrations were similar in middle-aged PE rats and young cyclic females on proestrus, while FSH levels were significantly greater in PE rats. After withdrawal of LHRH-AG treatment, plasma FSH concentrations remained elevated in PE rats as compared to young rats despite similar increases in E2. However, increases in plasma inhibin were delayed and significantly attenuated in PE rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of immunoradiometric and bioactive follicle stimulating hormone secretion and clearance in young and elderly men during treatment with tamoxifen or flutamide

The secretion and clearance of immunoactive and bioactive follicle-stimulating hormone (FSH) in healthy young men (N = 10) and elderly men (N = 7) during blockade of endogenous sex steroid hormones with tamoxifen, an antiestrogen, and flutamide, an antiandrogen, was investigated. To this end, subjects underwent blood sampling basally every 10 minutes for 24 hours, and then received 2 consecutive intravenous pulses of synthetic gonadotropin releasing hormone (GnRH; 10 micrograms and 100 micrograms) every 2 hours. This paradigm was repeated on two subsequent visits, in which subjects received either flutamide HCl, a specific nonsteroidal competitive antagonist of the androgen receptor (750 mg daily for 3 days), or tamoxifen, a selective antagonist of the estrogen receptor (20 mg daily for 9 days). Serum immunoactive FSH concentrations were measured in each sample by immunoradiometric assay (IRMA). Serum bioactive FSH concentrations were determined by an in vitro bioassay (rat granulosa cell aromatase system) on 24-hour serum pools. Deconvolution analysis was used to analyze both the FSH IRMA 24-hour time series and FSH release after GnRH. Comparisons between young and elderly men of the basal state showed significantly increased 24-hour mean serum immunoactive and bioactive FSH concentrations and significantly decreased free testosterone concentrations in elderly men. By deconvolution analysis, elderly men had a significant decrease in FSH secretory burst duration, and an increase in FSH half-life and FSH secretory burst amplitude compared with younger men. In response to sex steroid receptor blockade in young men, there was a significant increase in mean serum bioactive FSH concentrations during antiandrogen treatment, but not during antiestrogen treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of a single serum LH measurement in women with cycle disturbances: discrepancies between immunoreactive and bioactive hormone estimates

OBJECTIVE

We evaluated the significance of single serum LH estimates (as assessed by radiometric assay (IRMA) and Leydig cell in-vitro bioassay (BIO)) for the diagnosis of polycystic ovary syndrome (PCOS) in women with infertility and cycle abnormalities.

DESIGN

Hormonal and clinical comparisons between subgroups were made based on classification according to (a) rigid clinical and endocrine (excluding LH) characteristics of PCOS, (b) elevated IRMA-LH concentrations, (c) BIO-LH levels. In addition, androgen modulation of LH biopotency was studied in these patients.

PATIENTS

Ninety-nine women presenting at our infertility Unit with oligo/amenorrhoea.

MEASUREMENTS AND RESULTS

Of the total study group, 35 women were diagnosed positive as PCOS and 42 showed elevated IRMA-LH levels. Only 51% (n = 18) of PCOS patients showed elevated IRMA-LH levels, and in PCOS significantly higher levels of BIO-LH, androstenedione, oestrone, and BIO/IRMA-LH ratios were found as compared to non-PCOS patients. In the group with elevated IRMA-LH only 43% (n = 18) of subjects were diagnosed as PCOS, and no difference in BIO/IRMA-LH ratios was found. With increasing BIO-LH levels the probability of PCOS rises sharply (P < 0.001), whereas this probability is of only marginal significance (P < 0.06) for IRMA-LH. In the total study group a correlation is observed between serum testosterone (T) levels and IRMA-LH (r = 0.47), and BIO-LH (r = 0.51) concentrations. This correlation is absent comparing serum T and BIO/IRMA-LH ratios (r = 0.15).

CONCLUSIONS

Results presented in this study indicate that (1) women with infertility and oligo/amenorrhoea classified based on signs of PCOS or IRMA-LH levels, exhibit different clinical and endocrine characteristics, (2) only 51% of PCOS women exhibit elevated IRMA-LH concentrations, and only 43% of women with elevated IRMA-LH were diagnosed as PCOS, (3) IRMA-LH levels are a poor predictor of PCOS, whereas the predictive value of BIO-LH is better, (4) elevated BIO/IRMA-LH ratios in PCOS are dependent on alterations in BIO-LH, rather than IRMA-LH concentrations, and (5) no correlation was observed between serum T levels and BIO/IRMA-LH ratios.

Differential regulation in the release of bioactive versus immunoactive gonadotropins from cultured rat pituitary cells by inhibin and androgens

Using in vitro bioassays and radioimmunoassays, the authors examined the interactions between purified 32kD ovine inhibin, testosterone, and dihydrotestosterone on basal and GnRH-stimulated secretion of gonadotropins in primary rat pituitary cell cultures. This study demonstrates that inhibin and androgens: 1) differentially regulate gonadotropin levels, 2) cause changes in the amounts of bioactive and immunoactive FSH and LH released. In conclusion, differences in bio- and immuno-FSH and LH secretion suggest that the endocrine milieu results in not only quantitative but qualitative changes in the secreted gonadotropin isoforms.

Onset and characteristics of the midcycle surge in bioactive and immunoactive luteinizing hormone secretion in normal women: influence of physiological variations in periovulatory ovarian steroid hormone secretion

Limited studies in nonhuman primates suggest that the midcycle LH surge is characterized by distinctly different patterns of bioactive (LH-BIO) and immunoactive (LH-RIA) LH secretion. To further examine the patterns of midcycle LH-BIO and LH-RIA secretion and explore the influence of physiological variations in steroid hormone feedback on LH surge dimensions we studied seven normal ovulatory women over the periovulatory interval. In each, blood samples were obtained every 3 h and transvaginal ultrasonography was performed every 12 h over a 5-7 day interval at midcycle. Serum levels of LH-RIA, FSH, estradiol (E2), progesterone (P4), and 17-hydroxyprogesterone were determined by RIA; LH-BIO was estimated using a mouse leydig cell bioassay. Hormone data were standardized to the time of surge onset in LH-RIA (time zero), defined as a 100% increase above a 6-point running mean baseline value; surge cessation was defined as a decline to below baseline concentration. Mean LH-RIA surge duration was 54.0 +/- 4.0 h. LH-BIO surge onset was simultaneous with that of LH-RIA and coincident with the peak in E2 levels (mean data). Mean P4 and 17-hydroxyprogesterone rose in a parallel, phasic manner, an abrupt increase in slope occurred between -6 h and +30 h but an acute rise in P4 was not consistently observed among individuals. The surge onset to follicle rupture interval (mean 37.6 +/- 4.2 h) positively correlated with peak LH-RIA (r = 0.76, P less than 0.05), surge amplitude (r = 0.74, P less than 0.05) and surge onset to peak interval (r = 0.87, P less than 0.02), but not surge duration. There were no significant relationships between E2 or P4 (mean, peak, integrated, slope) and surge amplitude or duration (LH-RIA, FSH), peak value, or surge onset to peak interval (LH-RIA, LH-BIO, FSH). These data suggest that in women, 1) onset of the midcycle surge in LH-RIA and LH-BIO is simultaneous, and 2) surge characteristics are not influenced by physiological variations in steroid hormone secretion that occur beyond the thresholds required for surge initiation.

The Sulawesi Crested Black Macaque (Macaca nigra) menstrual cycle: changes in perineal tumescence and serum estradiol, progesterone, follicle-stimulating hormone, and luteinizing hormone levels

Events in the normal menstrual cycle of the endangered Sulawesi Crested Black Macaque (Macaca nigra) were characterized. Daily blood samples were obtained during 10 menstrual cycles from five M. nigra demonstrating regular cycles. The amount of perineal tumescence was scored daily. Serum levels of estradiol and progesterone were determined by RIA, serum LH levels were determined by the mouse Leydig cell bioassay, and serum FSH levels were determined by the rat granulosa cell aromatase bioassay. Cycle length was 39.8 +/- 1.0 days (mean +/- SEM) with an LH surge occurring 25 +/- 1.5 days from the onset of menses. After menses, both LH and estradiol were initially depressed, with estradiol first exceeding 50 pg/ml 8 days before the LH surge. In five cycles, peak estradiol levels (340 +/- 44 pg/ml) occurred on the day of the LH surge (637 +/- 58 ng/ml) and in the other five cycles, on the day before the LH surge. There was a broad increase of FSH in midcycle without a well-defined surge corresponding to the LH surge. Progesterone began increasing on the day of the LH surge and reached peak levels (6.8 +/- 0.96 ng/ml) 8 days later. Maximal perineal tumescence was generally associated with the time of the LH surge, but variation between animals made it impossible to predict accurately the day of the LH surge by perineal tumescence scores alone.

Inhibin production by macaque granulosa cells from pre- and periovulatory follicles: regulation by gonadotropins and prostaglandin E2

Although inhibin (IN) is secreted by granulosa cells (GC) of preovulatory follicles, the major source of immunoreactive IN circulating during the primate ovarian cycle is the corpus luteum. The aims of this study were (1) to investigate culture conditions for optimal IN production by luteinized GC (LGC) from rhesus monkeys and (2) to compare IN and progesterone (P) production by nonluteinized GC (NGC) and LGC in response to putative agonists. Animals were treated for up to 9 days with human menopausal gonadotropins to promote the development of multiple preovulatory follicles. GC were obtained from large follicles before (NGC) or 27 h after (LGC) an ovulatory injection of hCG. For Aim 1, cells were cultured in Hams F-10 medium +/- hCG (100 ng/ml) with or without the addition of insulin/transferrin/selenium, 10% fetal bovine serum, or 10% Serum-Plus (JRH Biosciences, Lenexa, KS). Medium was changed on Days 1, 2, 4, 6, and 8, and IN and P concentrations were determined by RIA. Basal (unstimulated) IN production by LGC was enhanced and maintained for 6-8 days in the presence of serum, but rapidly declined in the absence of serum. In contrast, basal P secretion declined regardless of exposure to serum. Human CG consistently increased (p less than 0.05) IN production only in the presence of serum but stimulated (p less than 0.05) P production under all conditions. For Aim 2, cells were cultured for 4 days in Ham's F-10 medium + 10% macaque serum +/- hCG (100 ng/ml), hFSH (100 ng/ml), prostaglandin E2(PGE2; 14 microns), or dibutyryl(db)-cAMP (5 mM).(ABSTRACT TRUNCATED AT 250 WORDS)

FSH isoforms, radioimmunoassays, bioassays, and their significance

Follicle-stimulating hormone (FSH) plays a central role in steroidogenesis and gametogenesis. In recent years, a great deal has been learned about the microheterogeneity of FSH using newly developed assay techniques. This review article will attempt to discuss the advantages and the limitations of recently developed and commonly used assay systems.

Serum bioactive and immunoreactive luteinizing hormone and follicle-stimulating hormone levels in women with cycle abnormalities, with or without polycystic ovarian disease

Serum steroid, gonadotropin, and alpha-subunit levels were assessed in 35 women with cycle abnormalities [11 with and 24 without polycystic ovarian disease (PCOD) according to strict clinical and biochemical criteria] and 8 regularly cycling women in the early (cycle day 3 or 4) and mid (cycle day 7 or 8) follicular phase. LH and FSH levels were estimated using two immunological techniques [RIA and immunoradiometric assay (IRMA)] and in vitro bioassays (BIO), using mouse Leydig cells and rat granulosa cells, respectively. In PCOD patients mean alpha-subunit, free androgen index [FAI; testosterone x 100/sex hormone-binding globulin (SHBG)], androstenedione, estrone, and estradiol (E2) were significantly elevated compared to levels in the early follicular phase of control cycles and non-PCOD patients. In addition, in PCOD patients mean IRMA-LH and RIA-LH levels were distinctly increased (2.8- to 3.6 fold, respectively; both comparisons, P less than 0.001) compared to control values, but in the same order of magnitude (1.3- to 1.4-fold increments) as that in non-PCOD patients. However, the median BIO-LH level in PCOD patients was 5.9-fold higher than that in non-PCOD patients and 4.0-fold higher than the BIO-LH in the early follicular phase of control women. Consequently, the median BIO/IRMA-LH ratio was 4.8-fold higher in PCOD patients compared to non-PCOD patients. In women with cycle abnormalities, individual BIO/IRMA-LH ratios correlated with BIO-LH (rs = 0.48), FAI (rs = 0.39), free estrogens (E2/SHBG ratios; rs = 0 0.47), and dehydroepiandrosterone sulfate (rs = 0.60) concentrations. Mean IRMA-, RIA-, and BIO-FSH levels and BIO/IRMA-FSH ratios were not significantly different when various groups were compared. Although RIA- and IRMA-LH levels showed good correlation (rs = 0.88), RIA-LH levels were consistently higher, resulting in distinctly higher RIA-LH/FSH ratios (mean, 4.5) compared to IRMA-LH/FSH ratios (median, 1.8) in PCOD patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Medical treatment of endometriosis: a comparison of the suppressive effects of danazol and nafarelin on reproductive hormones

OBJECTIVE

Patients with endometriosis were studied to investigate hormonal suppression by the gonadotropin-releasing hormone against nafarelin acetate compared with danazol. We hypothesized that the pattern, time course, and degree of gonadotropin and ovarian suppression would be different.

DESIGN

The study included 16 patients who were randomized into one of three 6-month treatment protocols.

SETTING

Patients were recruited from a university hospital setting.

PATIENTS

Eligible candidates were 18 to 45 years of age, with regular menses and documented pelvic endometriosis.

INTERVENTION

Six-month treatment protocols included nafarelin 800 or 400 micrograms/d, or danazol 800 mg/d.

MAIN OUTCOME MEASURES

Serum estradiol (E2), progesterone (P), luteinizing hormone (LH), and follicle-stimulating hormone were determined before treatment and then monthly. Thirteen patients consented to a 12-hour hospital admission during the 5th and 6th month of treatment to determine LH pulse frequency and amplitude.

RESULTS

Estradiol and P were suppressed in all groups, but E2 significantly more by nafarelin than danazol (P less than or equal to 0.01). Nafarelin, 800 micrograms, significantly depressed LH pulse amplitude compared with danazol (P less than or equal to 0.05). Two patients in the nafarelin group had the administration of their medication observed, and both demonstrated single, high-amplitude pulses immediately after administration.

CONCLUSION

Nafarelin is a more potent LH and E2 suppressor than danazol, and the agonist effect of nafarelin may continue to provoke transient gonadotropin responses despite long-term therapeutic suppression.

Effects of follicular fluid administration on serum bioactive and immunoactive FSH concentrations and compensatory testicular hypertrophy in hemicastrated prepubertal rats

In prepubertal rats, removal of one testis (hemicastration) results in increased FSH secretion and a compensatory hypertrophy of the remaining testis. To determine whether these two events are related, testis weight was measured after inhibin-rich porcine follicular fluid (FF) was administered to hemicastrated rats twice daily for 14 days to block the compensatory rise in FSH. After hemicastration, serum immunoreactive FSH concentration approximately doubled and testis weight was increased by approximately 60%. A slight but non-significant increase in serum bioactive FSH was also observed. Treatment of hemicastrated rats with FF completely prevented the increase in serum FSH and compensatory growth of the remaining testis, whereas concomitant treatment of these animals with ovine FSH reversed the inhibitory effects of FF. Serum inhibin concentrations were determined using two radioimmunoassay (RIA) systems; one assay utilized an antiserum generated against intact bovine inhibin and the other was directed against an alpha-inhibin fragment. Both assays showed a decline in inhibin levels following hemicastration. In addition, increases in serum inhibin concentrations were observed following FF administration in both RIAs; however, the relative increase in inhibin over levels in hemicastrated rats was greater using the intact inhibin assay. In summary, these data suggest that the increase in FSH concentrations after hemicastration is related to a reduction in inhibin levels, and that this FSH rise is a primary signal for initiating compensatory testicular hypertrophy in prepubertal rats. Furthermore, exogenous FSH administration overcame the inhibitory effects of FF on the testes, suggesting that inhibin may not act directly at the gonadal level.

Photoperiodic differences in in vitro pituitary gonadotropin basal secretion and gonadotropin-releasing hormone responsiveness in the golden hamster

In order to examine pituitary gonadotropin secretion and responsiveness to GnRH after photic-induced changes in reproductive condition, an in vitro pituitary perifusion system was established for male golden hamster tissue. Anterior pituitaries from adult males which had been maintained on 14 h light:10 h dark (long days) or 6 h light:18 h dark (short days) for 10 weeks were perifused using an Acusyst perifusion system. Perfusates from unstimulated tissue (basal secretion) and from tissue stimulated with hourly pulses of GnRH (25, 50, or 100 ng/ml) were assayed for LH and FSH by RIA. Tissue from short-day animals had lower basal LH secretion than tissue from long day animals, but there were no significant photoperiodic differences for GnRH-stimulated LH secretion. In contrast, there were no photoperiodic differences in basal FSH secretion, but tissue from short-day animals secreted more FSH than tissue from long-day animals when stimulated with GnRH. Bioactivity of a small number of perfusate samples was assessed using in vitro rat granulosa cell and mouse Leydig cell assays for FSH and LH, respectively, and did not show any photoperiodic differences in LH or FSH bioactivity for GnRH-stimulated tissue. These studies indicate that the pituitaries of gonadally regressed hamsters are capable in vitro of responding to GnRH with similar or greater levels of gonadotropin release compared to pituitaries from animals with functional gonads. Therefore, it appears that the lowered serum gonadotropin levels seen in vivo in gonadally regressed animals are not due to a reduction in intrinsic pituitary sensitivity to GnRH.

Effects of follicular fluid administration on serum bioactive and immunoreactive FSH concentrations and compensatory testosterone secretion in hemicastrated adult rats

In adult rats, removal of one testis (hemicastration) results in an elevation of serum follicle-stimulating hormone (FSH) concentrations and a compensation in testosterone secretion by the remaining testis without a corresponding increase in testis size. To determine whether changes in FSH secretion and compensatory androgen production are related, serum testosterone concentrations were measured after inhibin-rich porcine follicular fluid was administered twice daily for 4 days to block the hemicastration-induced rise in FSH. Both serum immunoreactive FSH (immuno-FSH) and bioactive FSH (bio-FSH) concentrations were increased 4 days after hemicastration. The significant increase in serum immuno-FSH in hemicastrated animals was prevented by follicular fluid administration, whereas the serum bio-FSH activity and biologic to immunologic (B/I) ratios were increased in follicular fluid-treated animals. The follicular fluid-induced reduction in serum immuno-FSH had no effect on serum testosterone secretion in hemicastrated rats. Serum inhibin concentrations were reduced 27% in hemicastrated rats compared with intact controls, while administration of exogenous follicular fluid increased serum inhibin concentrations. An elevation in serum immuno-FSH secretion after hemicastration apparently is not required for the compensatory testosterone response. However, the observation of increased bio-FSH in hemicastrated and follicular fluid-treated animals raises questions about the importance of FSH quality (bioactivity), rather than quantity, for controlling testicular steroidogenic activity.

The induction of premature luteolysis in normal women--follicular phase luteinizing hormone secretion and corpus luteum function in the subsequent cycle

Women with luteal phase deficiency have been shown to have an increased frequency of luteinizing hormone pulses in the early follicular phase of the menstrual cycle. Because progesterone is known to modulate luteinizing hormone secretion, it has been hypothesized that the decreased progesterone secretion in a previous luteal phase deficiency cycle could lead to the abnormal luteinizing hormone secretory pattern in the ensuing early follicular phase. With the possibility that the higher luteinizing hormone pulse frequency might lead to another deficient luteal phase, it becomes conceivable that luteal phase deficiency could be self-perpetuating. To test this hypothesis, luteal phase deficiency was induced in six normal women by decreasing luteinizing hormone support of the corpus luteum with a gonadotropin-releasing hormone antagonist Nal-Glu, administered twice daily beginning in the midluteal phase after a control cycle. During the antagonist-treated luteal phase, each subject met the predetermined criteria for induced luteal phase deficiency: a 33% or greater decrease in integrated progesterone from the control cycle and an integrated progesterone level less than 100 ng/ml per day. Luteinizing hormone secretion patterns were determined by frequent blood sampling performed every 10 minutes for 12 hours in the early follicular phase of the control cycle and the cycle after antagonist administration. Daily luteal progesterone levels were measured in the control, treatment, and posttreatment cycles. Each volunteer served as her own control. Standard parameters were compared between the control and posttreatment pulse studies in the early follicular phase: (1) luteinizing hormone pulse frequency was 9.5 +/- 1.0 vs 10.0 +/- 0.9 pulses/12 hours, control vs posttreatment, respectively, p = 0.5; (2) luteinizing hormone pulse amplitude was 11.0 +/- 1.3 vs 12.0 +/- 2.2 ng/ml, p = 0.6; and (3) luteinizing hormone mean level was 19.4 +/- 2.3 vs 22.2 +/- 3.3 ng/ml, p = 0.1. Corpus luteum function was also compared between the control and posttreatment cycles. Luteal phase length was 13.7 +/- 0.6 vs 12.7 +/- 0.6 days, p = 0.08. Integrated progesterone values were 136.9 +/- 12.9 vs 130.5 +/- 11.3 ng/ml per day, p = 0.5. Therefore no discernible abnormalities in early follicular luteinizing hormone secretions or corpus luteum secretion of progesterone occurred after an induced luteal phase deficiency cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Specific regulatory actions of dihydrotestosterone and estradiol on the dynamics of FSH secretion and clearance in humans

The authors investigated immunoactive and bioactive follicle-stimulating hormone (FSH) secretion and clearance in six healthy young men during steady-state infusions of vehicle (basal, B, 28 hours), dihydrotestosterone (DHT, 4.5 days), or estradiol (4.5 days) accompanied by blood sampling at 10-minute intervals for 28 hours. Serum FSH concentrations were assayed by a two-site immunoradiometric assay (IRMA) and two separate in vitro bioassays (rat granulosa and Sertoli cell systems). FSH measurements included: 24-hour mean serum concentrations (IRMA and bioassay), multiple-parameter deconvolution of 24-hour pulsatile FSH time series and FSH release in response to exogenous gonadotropin-releasing hormone (GnRH) boluses (IRMA) to assess secretion and clearance, and circadian serum FSH concentration rhythms by cosinor analysis (IRMA). We found: 1) a significant decrease in 24-hour mean IRMA FSH concentrations during DHT infusion while both in vitro estimates of FSH bioactivity were unchanged; 2) significant decreases in the mass of IRMA FSH secreted per 24 hours during DHT infusion; 3) significant decreases in the IRMA FSH half-life during estradiol infusion without any change in FSH interpulse interval; 4) no steroidal effects on FSH secretory responses to exogenous GnRH; and 5) abolition of basal circadian FSH rhythms during sex-steroid infusions. Based on these findings, we conclude that steady-state sex-steroid hormone infusions selectively alter IRMA FSH secretion and clearance without affecting IRMA FSH pulse frequency or mean concentrations of bioactive FSH.

Increased bioactivity of serum follicle-stimulating hormone, but not luteinizing hormone, following hemicastration in ram lambs

This study evaluated the short-term effects of hemicastration on levels of bioactive (bio-) and immunoactive (immuno-) FSH and LH in 3.5-mo-old ram lambs. Biological activities of FSH and LH were determined using in vitro rat granulosa cell aromatase and mouse Leydig cell testosterone assays, respectively. Four rams each were either hemicastrated (HC) or left intact (INT) and blood samples were collected over a 2-wk period. In HC rams, serum bio- and immuno-FSH concentrations increased several fold within 5-8 h after surgery and remained elevated over INT controls for 7 and 14 days, respectively. The increase in bio-FSH was greater than that for immuno-FSH, resulting in an increase in the ratio of biological to immunological activity (B/I ratio) through Day 7. Neither immuno-FSH, bio-FSH, nor the B/I ratios varied throughout the 2-wk study in INT rams. In contrast to FSH, serum concentrations of immuno- and bio-LH and the B/I ratios were similar between HC and INT rams. For both gonadotropins, biological activity was positively correlated to immunological activity. These results demonstrate that (1) immuno- and bio-FSH concentrations are elevated after hemicastration; (2) the FSH biopotency (B/I ratio) also is increased, at least temporarily; and (3), despite these changes in FSH production, neither immuno- nor bio-LH secretion is altered by hemicastration.

Hormonal responses to a potent gonadotropin hormone-releasing hormone antagonist in normal elderly men

GnRH analogs, both agonists and antagonists, have potential use in androgen-dependent diseases of older men, such as prostatic cancer and benign prostatic hyperplasia. Previous experience with agonists of GnRH has suggested that GnRH analogs may be more effective in aged men than in young men, but little is known about GnRH antagonists in older men. Therefore, we evaluated the hormonal effects of a single dose and a short course of a GnRH antagonist (Nal-Glu) in normal elderly men. Six young men (25-34 yr old) and six older men (66-76 yr) each received single morning injections of Nal-Glu (25, 75, and 250 micrograms/kg), separated by 2 weeks. Serum levels of testosterone (T), immunoreactive LH (LH RIA) and FSH (FSH RIA), and bioactive LH (LH BIO) were evaluated periodically for 7 days after each injection. In addition, six elderly men received 25 and 75 micrograms/kg.day Nal-Glu for 10 consecutive mornings each, and serum levels of T, inhibin, LH RIA, LH BIO, FSH RIA, and bioactive FSH were evaluated. Nal-Glu in all three single doses caused a significant (P less than 0.01) decline in serum levels of T and gonadotropins that was similar in extent in the elderly and young men. For example, T declined to a level of 19% of baseline after the 250 micrograms/kg dose of Nal-Glu in both age groups. For both the young and elderly men, the major effect of increasing the Nal-Glu dose was a prolongation of the period of suppression. Multiple Nal-Glu injections in the elderly men also resulted in a rapid decline in T, inhibin, and bioactive and immunoreactive gonadotropins. For both LH and FSH, bioactivity decreased to a greater extent than immunoreactivity. Local side-effects of Nal-Glu tended to be fewer and of less intensity in the elderly men compared to those in the young men. These results demonstrate that the response to Nal-Glu in healthy elderly men is similar to that in younger men, and extended administration of Nal-Glu in elderly men effectively suppresses gonadal and pituitary function. These results suggest that the role of GnRH antagonists in the effective treatment of androgen-dependent disease in the aging male needs to be explored further.

Serum inhibin levels during the periovulatory interval in normal women: relationships with sex steroid and gonadotrophin levels

Inhibin is a gonadal glycoprotein believed to be important in the regulation of pituitary FSH secretion and/or to function as a paracrine factor within the ovary and testis. We studied serum levels of inhibin, oestradiol (E2), progesterone (P), FSH and LH during the periovulatory interval in order to determine whether there is differential control of sex steroid and inhibin secretion by the mature follicle and the emerging corpus luteum. Seven normal cyclic women were admitted 3-4 days prior to midcycle and blood samples drawn every 3 h for 5-7 days. Serum E2, P, FSH, LH and inhibin were measured by radioimmunoassay. Data were normalized around the peak LH value (0 h). Serum E2 and inhibin rose in parallel (r = 0.92, P less than 0.001) between -69 and -18 h, E2 reached a peak of 1296 +/- 154 (mean +/- SEM) pmol/l at -18 h, then fell to 1050 +/- 139 pmol/l at 0 h. Serum inhibin, on the other hand, continued to rise to a peak of 837 +/- 95 U/l at -6 h, fell to 455 +/- 48 U/l at +45 h, then rose again. On average, the peak inhibin level occurred 10.4 +/- 5.1 h after the peak E2 (P less than 0.05). Inhibin levels were positively correlated with both serum LH and FSH between -24 and +24 h (P less than 0.01). Serum E2 was negatively correlated with LH, FSH and inhibin between -24 and 0 h (P less than 0.01). Serum P levels increased from 1.8 +/- 0.3 nmol/l at -24 h to 14.3 +/- 1.0 nmol/l at +60 h. Serum inhibin was positively correlated with serum P from -24 to 0 h (P less than 0.01) and +45 to +60 h (P less than 0.01), but was inversely correlated from 0 to +45 h (P less than 0.01). We conclude that the maturing follicle secretes both E2 and inhibin in parallel until -18 h, at which time the process of luteinization is initiated by the onset of the midcycle LH surge, as evidenced by the rise in P. E2 secretion then falls while inhibin secretion rises, indicating different regulation of secretion of these two hormones by the maturing follicle. Furthermore, the close positive correlation between inhibin and gonadotrophin levels around midcycle suggests that FSH and/or LH stimulate inhibin secretion and that the presumed negative feedback effect of inhibin on FSH secretion is overcome at this time. After midcycle, inhibin secretion initially falls, then rises, while P rises progressively.(ABSTRACT TRUNCATED AT 400 WORDS)

Recombinant human activin-A stimulates basal FSH and GnRH-stimulated FSH and LH release in the adult male macaque, Macaca fascicularis

Activin-A is a homodimer of the beta A inhibin subunit that stimulates FSH secretion by pituitary cells in vitro; however, the physiological relevance of this effect is unknown. We have examined whether recombinant human activin-A (activin-A; 80 micrograms/kg/day iv infusion for 50.5 h) has in vivo bioactivity in the adult male macaque (n = 5). Serum FSH and LH bioactivity and serum testosterone (T) levels were measured on 2 control days and after 24 and 48 h of activin-A administration. Basal FSH levels increased significantly (p less than 0.05) by 17% at 24 h and 82% at 48 h during activin-A administration. No changes in basal LH or T levels were seen. The FSH and LH responses to GnRH (5 micrograms/kg, iv bolus) increased significantly (p less than 0.05) by 117% and 55% after 48 h of activin-A, respectively. A small (16%), but statistically significant (p less than 0.05), increase in the T response to the GnRH challenge was also noted. These data are preliminary evidence in support of a physiological role for activin-A in the control of gonadotropin secretion in the male primate.

Luteal phase deficiency: characterization of reproductive hormones over the menstrual cycle

The recurrent deficiency of progesterone (P) secretion by the corpus luteum has been associated with infertility and habitual abortion and given the clinical diagnosis of luteal phase deficiency (LPD). There is evidence that both follicular and luteal phase abnormalities can result in LPD cycles. In this study we have examined reproductive hormone levels and preovulatory follicular size in women with LPD (n = 10). For the purposes of this study, LPD was determined by an endometrial biopsy in the studied cycle that was more than 2 days out of phase. These biopsies were performed in women with infertility or habitual abortion who exhibited an out of phase biopsy in a prior cycle. The control group consisted of 28 normal women. Daily serum levels of the following hormones were determined in each subject: LH and FSH [immuno- and bioactive (LH-immuno and LH-bio)], P, estradiol (E2), and inhibin. The LPD women exhibited significant decreases in integrated luteal phase levels of inhibin [10,615 +/- 898 vs. 13,560 +/- 662 (U/L).days; P less than 0.02] and E2 [5,015 +/- 275 vs. 6,435 +/- 393 (pmol/L).days (1366 vs. 1753 (pg/mL).days); P less than 0.05] in addition to the expected decrease in P [280 +/- 23 vs. 420 +/- 23 (nmol/L).days (88 vs. 132 (ng/mL).days); P less than 0.01]. On days 6-11 after the LH surge (day 0), there was a significant (P less than 0.05) decrease in mean LH-bio levels in LPD compared with those in normal women (146 +/- 26 vs. 212 +/- 24 micrograms/L). The midcycle LH surge was deficient in LPD when both LH-immuno [482 +/- 30 vs. 672 +/- 43 (micrograms/L).days; P less than 0.01] and LH-bio [1711 +/- 179 vs. 2248 +/- 226 (micrograms/L).days; P less than 0.05] levels were compared with normal values. When comparing the follicular phase in LPD with that in normal women, similar follicle size, peak and integrated E2 levels, and mean LH and FSH (immuno and bio) levels were found. The only follicular phase abnormality noted in this study was decreased mean levels of serum inhibin in the early and midfollicular phases (221 +/- 19 vs. 308 +/- 25 U/L; P less than 0.01). In this group of women with LPD, low levels of inhibin in the follicular phase were consistent with the concept of a defect in function of the preovulatory follicle, possibly as a result of previously described defects in gonadotropin secretion in this condition.(ABSTRACT TRUNCATED AT 400 WORDS)

Suppression of bioactive and immunoreactive follicle-stimulating hormone and luteinizing hormone levels by a potent gonadotropin-releasing hormone antagonist: pharmacodynamic studies

Dose-dependent gonadotropin suppression by a potent gonadotropin-releasing hormone (GnRH) antagonist, Nal1 Glu6 [( Ac-D2Nal1,D4ClPhe2,D3Pal3,Arg5,DGlu(AA)6,- DAla10]GnRH), was determined in five postmenopausal women by frequent sampling for immunoreactive luteinizing hormone (I-LH) and immunoreactive follicle stimulating hormone (I-FSH) for 72 hours after single intramuscular (IM) injections of 10, 50, 150, and 300 micrograms/kg. Bioactive (B) LH and B-FSH also were measured after the IM administration of the 50-micrograms/kg dose. Serum levels of Nal1 Glu6 were determined by a radioreceptor assay for the first 24 hours after the 50-micrograms/kg IM dose and in three women after a 10-micrograms/kg intravenous (IV) dose. While the disappearance rate of serum Nal1 Glu6 after a 10-micrograms/kg IV injection was rapid, gonadotropin suppression persisted longer than detectable serum levels. In contrast, after a 50-micrograms/kg IM injection, the decline from peak circulating levels was slower, contributing to its longer duration of action (greater than 24 hours). All IM doses tested resulted in a similar 51% to 63% decrease in I-LH, which was maximal by 8 hours. The duration of action was dose-dependent, with decreased levels lasting up to 72 hours at the 300-micrograms/kg dose. While decline of I-FSH was smaller (14% to 33%), the duration of suppression was also dose-dependent, although the nadir occurs later (8 to 9 hours after administration) and suppression lasted longer (72 hours at the 150-micrograms/kg dose). The reduction of B-LH was greater than that of I-LH and the suppression of B-FSH also was greater than that of I-FSH.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of diverse mammalian and nonmammalian gonadotropins in a rat granulosa cell bioassay for follicle-stimulating hormone

The biopotencies of pituitary gonadotropins purified from a marsupial (kangaroo), two avian (ostrich and turkey), a reptile (turtle), an amphibian (bullfrog), and two fish (sturgeon and teleost) species were examined using an in vitro rat granulosa cell bioassay for follicle-stimulating hormone (FSH). Treatment of cultured granulosa cells with increasing concentrations of gonadotropin preparations from these species resulted in dose-dependent increases in estrogen production from negligible amounts to maximal levels of approximately 2-29 ng/culture. The relative biopotencies of these FSH preparations from most potent to least potent were in the order of human greater than ostrich greater than turkey greater than kangaroo greater than turtle greater than sturgeon greater than bullfrog greater than teleost with ED50 values of human 8.7 ng/well; ostrich 10.5 ng/well; turkey 22.5 ng/well; kangaroo 58.2 ng/well; turtle 62.5 ng/well; sturgeon 260 ng/well; bullfrog 750 ng/well; teleost greater than 1000 ng/well. In contrast, luteinizing hormone (LH) preparations were considerably less effective for ostrich, turkey, kangaroo, turtle, and bullfrog, being six-, five-, three-, and twofold less potent than FSH preparations for the same species, demonstrating the specificity of this assay for FSH. An LH preparation from bullfrog was unable to significantly stimulate estrogen production below 500 ng/ml. Thus, the present in vitro bioassay (GAB) using rat granulosa cells provides a sensitive and specific assay for measuring FSH activities of gonadotropins from diverse mammalian and nonmammalian species.

Monitoring ovarian function and pregnancy in the giant panda (Ailuropoda melanoleuca) by evaluating urinary bioactive FSH and steroid metabolites

Urinary excretion of oestrone conjugates, pregnanediol-3 alpha-glucuronide (PdG) and 20 alpha-hydroxypregn-4-en-3-one were measured from 8 weeks before oestrus to 2 weeks post partum and bioactive FSH was monitored during the periovulatory interval in a female giant panda. A biphasic urinary bioactive FSH excretory profile appeared to indicate a broad (approximately 10 day) follicular phase followed by a sharp preovulatory bioactive FSH surge coincident with an acute increase in urinary oestrone conjugates and behavioural oestrus. Weekly concentrations of urinary oestrone conjugates and PdG increased (P less than 0.001) by Week 9 of gestation with 20 alpha-hydroxypregn-4-en-3-one levels increasing 10-30-fold (P less than 0.001) between Weeks 11 and 14. These observations indicate that the monoestrous giant panda does not appear to require a prolonged period of endogenous FSH release or multiple FSH peaks for ovarian priming and follicle selection to proceed normally. Furthermore, the delayed rise in urinary steroid excretion during the second half of gestation in the giant panda supports the concept of delayed implantation while the estimation of steroid conjugates in urine offers a non-invasive approach for monitoring pregnancy status in this endangered species.

Urinary concentrations of ovarian steroid hormone metabolites and bioactive follicle-stimulating hormone in killer whales (Orcinus orchus) during ovarian cycles and pregnancy

Reproductive hormone profiles of six captive killer whales (Orcinu orcus) from three Sea World aquaria were studied for intervals up to 2 yr. Daily urine samples and bimonthly blood samples were collected and analyzed for hormone concentration. Immunoreactive estrone conjugates, pregnanediol-3-glucoruonide, 20-alpha-hydroxyprogesterone as well as bioactive follicle-stimulating hormone (FSH) were measured in urine samples and indexed by creatinine concentrations of the same sample. In selected cases, serum progesterone concentrations were also measured. Three of the animals in the study became pregnant during the study period and two of these animals were evaluated during the time of conception and throughout most of gestation. From the data of the three animals that conceived, hormone profiles of the complete ovarian cycle, early pregnancy, and mid- to late gestation are described. The remaining three animals did not conceive and only one of these demonstrated hormone changes that indicated regular ovarian activity. The female reproductive pattern of the killer whale is characterized by a gestation of 17 mo and an ovarian cycle of 6-7 wk in duration. The hormone changes associated with the ovarian cycle of the killer whale are similar to those of most other mammalian species. A bimodal pattern of bioactive FSH with a pronounced rise of estrogen predominates the preovulatory hormone profile. After ovulation, increased progesterone production is observed for approximately 4 wk in the nonconceptive ovarian cycle. During the luteal phase and early pregnancy, when progesterone metabolites are elevated, estrogen metabolite excretion remains low. These data extend the application of urine collections for longitudinal studies involving hormone changes, particularly those involving nondomesticated species.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased serum inhibin levels in normal elderly men: evidence for a decline in Sertoli cell function with aging

Compared to young men, normal elderly men have decreased sperm production despite elevated serum gonadotropin levels. To determine whether the seminiferous tubule defect in elderly men includes decreased Sertoli cell function, we measured serum immunoreactive inhibin concentrations in young and elderly men before and after clomiphene citrate (CC) administration. Thirty-eight healthy men, 19 young (aged 22-35 yr) and 19 elderly (aged 65-85 yr), were studied before CC administration. The mean baseline serum inhibin level was significantly lower (P less than 0.001) in the elderly men than in the young men [416 +/- 22 (+/- SE) vs. 588 +/- 30 U/L], while serum immunoreactive FSH and LH levels were higher in the older men, and bioactive FSH levels were similar in the two age groups. Eleven young men and 13 elderly men were studied after 1 week of CC administration. The mean serum inhibin level increased by 71%, from 566 +/- 36 to 970 +/- 82 U/L, in the young men, but it increased by only 24%, from 421 +/- 26 to 520 +/- 38 U/L, in the elderly men. Serum immunoreactive LH and bioactive and immunoreactive FSH concentrations increased to similar levels in both groups after CC administration. We conclude that the seminiferous tubule defect of elderly men includes decreased Sertoli cell function.

Bioactive follicle-stimulating hormone levels in serum and urine of male and female rats from birth to prepubertal period

Using a sensitive in vitro granulosa cell aromatase bioassay (GAB), we determined serum and urinary levels of bioactive follicle-stimulating hormone (bio-FSH) in male and female rats from birth to Day 40 of age. In addition, serum immunoreactive FSH (immuno-FSH) was measured by radioimmunoassay to determine the bio- to immuno-(B/I) ratio of FSH. During the neonatal period (Days 1-7 of age), both sexes had detectable serum bio-FSH levels. In the infantile period (Days 7-21), serum bio-FSH levels initially decreased at Day 10 for both sexes, and then rose steadily, reaching maximum concentrations at Day 14 (males: 68.7 ng/ml; females: 114.6 ng/ml). Subsequently, FSH levels in the females decreased from Day 16 throughout the juvenile (Days 21-35) and prepubertal (Days 35-40) periods. In contrast, FSH levels in the males fluctuated during these periods. In the males, immuno-FSH reflected the bioactive profiles, with a B/I ratio of 2.2 +/- 0.2. In the females, the B/I ratio was approximately 2.5 during the neonatal and infantile periods but declined to approximately 1.0 during the juvenile and prepubertal periods, consistent with earlier observations of heterogeneous forms of pituitary FSH in immature female rats. Morning urine samples were also collected daily and bio-FSH concentrations were determined. In both sexes, urinary bio-FSH profiles were highly correlated (r = 0.93) with serum FSH throughout development. However, the urine concentrations were about 50-fold higher than serum.(ABSTRACT TRUNCATED AT 250 WORDS)

A factor(s) produced by Sertoli cells stimulates androgen biosynthesis by Leydig cells in neonatal rats

Using a coculture system, we have studied the local action of Sertoli cells on Leydig cell function. The results show that (i) both LH and FSH have equal potency to stimulate testosterone biosynthesis by fetal and neonatal testicular cells in an age-dependent manner, the maximum stimulation is observed between D3 and D5. (ii) An FSH-dependent factor(s) secreted by Sertoli cells increases the basal and/or LH-stimulated Leydig cell androgen production. (iii) The Sertoli cell-stimulating factor(s) is not a steroid or other small molecule, but a heat-labile peptide.

Maintenance of the ratio of bioactive to immunoreactive follicle-stimulating hormone in normal men during chronic luteinizing hormone-releasing hormone agonist administration

Chronic administration of LHRH agonist analogs to humans reduces gonadal function through pituitary desensitization. Serum immunoreactive gonadotropin levels are modestly reduced, whereas serum bioactive LH levels are drastically suppressed. The effects on bioactive FSH levels, however, are not known. In this study, serum bioactive FSH was measured using an in vitro granulosa cell aromatase bioassay in four normal men given a LHRH agonist, [D-Trp6,Pro9-NEt]LHRH (LHRHA; 500 micrograms/day for 16 weeks), by sc infusion and testosterone enanthate (TE; 100 mg, im every 2 weeks) and in five men given 500 micrograms/day LHRHA by daily sc injection for 20 weeks and TE (100 mg every 2 weeks) from weeks 10 through 20. During the first study, serum immunoreactive FSH levels (IR-FSH) decreased by 56.5 +/- 4.8% (+/- SEM), and serum bioactive FSH (Bio-FSH) level decreased by 57.6 +/- 6.4%. The ratio of Bio-FSH to IR-FSH did not change. During the second study, both serum IR-FSH and Bio-FSH levels followed a triphasic pattern, decreasing slightly but not significantly immediately after initiation of LHRHA administration, progressively increasing to a peak (P less than 0.5 vs, baseline) at week 10, and then, after addition of TE to this regimen, decreasing slightly again. The Bio-FSH to IR-FSH ratio, as in the first study, did not change. When serum obtained at week 10 during the second study, just before initiation of TE, was chromatographed on a Sephadex G-100 column, IR-LH eluted in two distinct peaks, while IR-FSH eluted as a single peak. These results demonstrate that in normal men chronic LHRHA administration alone for up to 10 weeks or LHRHA plus TE for up to 16 weeks does not alter the qualitative characteristics of secreted FSH, since there was no dissociation between serum IR- and Bio-FSH levels.

The dependency of bioactive follicle-stimulating hormone secretion on gonadotropin-releasing hormone in hypogonadal and cycling women

An antagonist analog of GnRH, (Ac-delta 3-Pro1,p-F-D-Phe2,D-Trp3,6)GnRH (4F-antagonist), was administered to normal women and women with hypergonadotropic hypogonadism. Serum FSH levels were determined by both the granulosa cell aromatase bioassay and RIA. The constant infusion of 4F-antagonist (30 micrograms/kg.h) to the four hypogonadal women resulted in a more pronounced decline in bioactive FSH (62%) than in immunoreactive FSH levels (30%), and the FSH bioactive to immunoreactive ratio decreased significantly (P less than 0.05). Infusion of 4F-antagonist in normal women in the midfollicular phase revealed a similar pattern of suppression of bioactive (64%) and immunoreactive FSH (29%). When 4F-antagonist was administered sc at a dose of 80 micrograms/kg twice daily for 3 days to normal women in the midfollicular phase of their cycles, the bioactive FSH response was biphasic, with the maximal decrease on the second day, followed by return to basal levels on the third day. Correspondingly, there was a precipitous decline in serum estradiol (apparent demise of the dominant follicle), followed by a progressive rise in estradiol levels. Thus, in contrast to immunoreactive FSH levels, bioactive FSH more clearly reflects the biological action of FSH on the follicle in response to GnRH antagonist administration in women. The disparity in the quantitative decline between serum bioactive and immunoreactive FSH levels after presumed blockade of the GnRH receptor may reflect the microheterogeneity of the FSH molecule and suggests that alterations in the biological activity of secreted FSH may be GnRH dependent.

Serum bioactive and immunoreactive follicle-stimulating hormone in prostatic cancer patients during gonadotropin-releasing hormone agonist treatment and after orchidectomy

Serum bioactive and immunoreactive FSH levels were measured in five prostatic cancer patients during treatment for 6 months with the GnRH agonist analog buserelin (Hoechst; 600 micrograms, intranasally, 3 times per day) and for up to 12 weeks after subsequent orchidectomy. FSH bioactivity was measured using a sensitive specific in vitro granulosa cells aromatase bioassay. Before buserelin treatment, mean serum FSH bioactivity and immunoreactivity were 19.7 +/- 4.1 (+/- SE) IU/L (n = 5) and 13.7 +/- 3.8 IU/L, respectively, with a bioactivity to immunoactivity (B/I) ratio of 1.7 +/- 0.2. After the initiation of treatment with the GnRH agonist, FSH bio- and immunoactivities both transiently increased for 1-3 days. The increase in bioactivity was greater and prolonged, and the B/I ratio increased nearly 7-fold in 2 weeks. Serum FSH immunoreactivity declined to below the pretreatment level in 5 days and remained low for the rest of the treatment period. In contrast, serum FSH bioactivity did not decrease significantly below the pretreatment level during the 6-month treatment period, although the B/I ratio returned slowly toward the pretreatment value. After orchidectomy, both FSH activities increased dramatically, and the B/I ratio rose transiently from 1.5 to 7 in 2 weeks. Interestingly, serum FSH bioactivity and immunoreactivity decreased significantly (P less than 0.05) 1 day after orchidectomy in the buserelin-treated patients. In contrast, serum FSH immunoreactivity increased during the same period (P less than 0.05) in patients treated only by orchidectomy (FSH bioactivity was not measured). In conclusion, serum FSH bioactivity increases acutely more than FSH immunoreactivity after initiation of GnRH agonist treatment or orchidectomy. In the former case, serum FSH bioactivity subsequently returned to the pretreatment range. A clear decline during long term agonist treatment occurred only in serum FSH immunoreactivity, in contrast to the concomitant decline in serum LH bio- and immunoreactivities reported previously. The persistence of bioactive FSH may explain the inconsistent effects of GnRH agonist treatment on the suppression of spermatogenesis. The acute decrease in serum FSH after orchidectomy in the buserelin-treated men suggests that the testes may produce a factor that stimulates pituitary FSH secretion.

Naturally occurring antihormones: secretion of FSH antagonists by women treated with a GnRH analog

Follicle-stimulating hormone (FSH) is a glycoprotein essential for gonadal development and steroidogenesis. Recent studies suggest that deglycosylation of FSH results in the formation of antagonistic proteins that are capable of binding to gonadal receptors but that are devoid of bioactivity. Treatment of hypogonadal women with an antagonist of gonadotropin-releasing hormone substantially decreased serum FSH bioactivity with minimal changes in immunoreactivity. Chromatofocusing and size fractionation of the serum samples indicated the secretion of immunoreactive FSH isoforms that are devoid of bioactivity but that are capable of blocking FSH action in ovarian granulosa cells. These findings provide the first demonstration of naturally occurring circulating antihormones. These FSH antagonists may play an important role in the physiology and pathophysiology of the gonads.

Use of the granulosa cell aromatase bioassay for measurement of bioactive follicle-stimulating hormone in urine and serum samples of diverse species

Ovarian steroids and growth factors are intragonadal modulators which augment a key endpoint of follicle-stimulating hormone (FSH) action in granulosa cells: the induction of aromatase activity. Studies of these paracrine hormones that enhance FSH-stimulated estrogen biosynthesis by cultured rat granulosa cells, have led to the development of a sensitive and specific in vitro bioassay for FSH. This newly developed granulosa cell aromatase bioassay (GAB) allows for the measurement of bioactive FSH levels in serum and urine of humans and animals with various physiological and pathological conditions. These studies have demonstrated that the GAB assay is useful in detecting possible changes in the molecular forms of FSH. The adaptation of this method for urine samples allows for the measurement of bio-FSH levels in situations where venipuncture is not practical or in species for which specific radioimmunoassays are not available.

Serum bioactive follicle-stimulating hormone in men with idiopathic azoospermia and oligospermia

Using an in vitro granulosa cell aromatase bioassay (GAB), serum bioactive FSH (bio-FSH) levels were measured in 20 fertile men and 74 men with idiopathic azoospermia or oligospermia. The serum bio-FSH levels measured by the GAB assay and the immunoreactive FSH (immuno-FSH) levels measured by RIA were positively correlated (r = 0.93). Compared to normal men, serum bio-FSH and immuno-FSH levels were elevated in patients with idiopathic azoospermia associated with severe germinal epithelium damage; the bioactive to immunoreactive ratio (B:I ratio) of FSH in these men [mean, 1.5 +/- 0.5 (+/- SD)] was significantly lower than that in fertile men (2.7 +/- 0.8). Similarly, in men with moderate and severe oligospermia, the B:I ratios of FSH were decreased (1.4 +/- 0.4 and 1.7 +/- 0.3, respectively). Although serum immuno-FSH levels correlated weakly with mean sperm concentrations in the normal and oligospermic men (r = -0.35), no relationship was found between serum bio-FSH and sperm concentrations. The B:I ratio of FSH correlated weakly with sperm concentration (r = 0.46). These findings suggest that the B:I ratio of FSH measured by the GAB assay decreases in patients with low sperm concentrations and germinal cell failure.