Comparison of inhibin B and estradiol responses to intravenous FSH in women with polycystic ovary syndrome and normal women

BACKGROUND

Inhibin B (Inh B) is produced by pre-antral and early antral follicles whereas estradiol (E(2)) is a product of follicles undergoing antrum formation. This temporal distinction is evident in the patterns of Inh B and E(2) release earlier and later during the follicular phase of the menstrual cycle, respectively. However, in previous studies of women with polycystic ovary syndrome (PCOS) and normal controls, release of these granulosa cell (GC) products appears to be simultaneous in response to FSH stimulation. In order to reconcile these disparate findings, we conducted dose-response studies in both PCOS women and normal controls to determine whether GC product responses were due to the amount of FSH administered. In addition, we compared FSH-stimulated responses in PCOS women at various stages of recovery following ovarian suppression with a long-acting GnRH agonist to examine whether Inh B and E(2) responses reflected the level of ovarian follicle activity (i.e. circulating E(2) levels).

METHODS

Women with PCOS, 18-35 years (n = 23), and normal ovulatory controls, 18-35 years (n = 10) were recruited for study. Dose-responses were assessed over 24 h following intravenous administration of 0 (saline), 37.5, 75 and 150 IU of recombinant human FSH (r-hFSH) in PCOS and normal women. In addition, E(2) and Inh B responses to 150 IU of r-hFSH were assessed at baseline and 4, 6 and 8 weeks following suppression of ovarian steroidogenesis by a long-acting GnRH agonist in PCOS women.

RESULTS

In PCOS women and normal controls, serum Inh B and E(2) exhibit similar and simultaneous dose-responsiveness to FSH stimulation. During recovery from ovarian suppression, basal and stimulated Inh B release appear to be restored earlier than that of E(2) in PCOS women.

CONCLUSIONS

These findings are consistent with the notion that, in PCOS women, the level of ovarian follicle activity largely determines the earlier release of Inh B compared with E(2).

Increased androgen response to follicle-stimulating hormone administration in women with polycystic ovary syndrome

CONTEXT

In women with polycystic ovary syndrome (PCOS), excess ovarian androgen production is driven by increased LH secretion. Studies conducted in animals suggest that the granulosa cell may influence LH-stimulated theca cell androgen production.

OBJECTIVE

The objective of this study was to determine whether FSH enhances androgen production in women with PCOS compared with that of normal women.

DESIGN

A prospective study was conducted to compare androgen production in response to FSH in two groups of women.

SETTING

The study was conducted in a General Clinical Research Center in a tertiary academic medical center.

PATIENTS

Women with PCOS, 18-35 yr (n = 20), and normal ovulatory controls, 18-35 yr (n = 10), were recruited for study.

INTERVENTIONS

Serial blood samples were obtained over a 24-h period after an iv injection of recombinant human FSH (150 IU).

MAIN OUTCOME MEASURES

The main outcome measures were serum 17-hydroxyprogesterone (17-OHP), androstenedione (A), dehydroepiandrosterone (DHEA), testosterone (T), and inhibin B (Inh B) responses after FSH administration.

RESULTS

Basal serum 17-OHP, A, and T levels were markedly increased in women with PCOS compared with that observed in normal women. Basal DHEA and Inh B levels were similar to those of normal controls. After FSH injection, PCOS women demonstrated enhanced production of 17-OHP, A, DHEA, and Inh B, whereas in normal women no increases were observed. T levels declined slightly in both groups.

CONCLUSIONS

These findings provide evidence that, in PCOS women, theca cell androgen production is enhanced by FSH administration and suggest a granulosa-theca cell paracrine mechanism.

Serum anti-mullerian hormone concentrations are not altered by acute administration of follicle stimulating hormone in polycystic ovary syndrome and normal women

CONTEXT

In the human ovary, expression of anti-Mullerian hormone (AMH) is detected primarily in granulosa cells of preantral and small antral follicles. This finding is consistent with the tight correlation between circulating AMH levels and the number of small antral follicles (2-5 mm) in normal and polycystic ovary syndrome (PCOS) women. In addition, the greater follicle count in PCOS is mirrored by significantly higher serum AMH levels compared with those of normal women. Despite the utility of AMH measurements in evaluating ovarian physiology and function, the regulation of AMH remains poorly understood.

OBJECTIVE

The objective was to determine whether gonadotropins acutely regulate serum AMH in women with PCOS and normal women.

DESIGN

We conducted a prospective study to compare ovarian responses to FSH in two groups of women.

SETTING

The study was conducted in a General Clinical Research Center in a tertiary academic medical center.

PATIENTS

Women with PCOS (age, 18-35 yr; n = 16) and normal ovulatory controls (age, 18-35 yr; n = 11) were recruited for study.

INTERVENTIONS

Serum samples were measured over a 24-h period after an iv injection of recombinant human FSH (150 IU).

MAIN OUTCOME MEASURE(S)

Serum AMH responses after FSH administration were measured.

RESULTS

Basal serum AMH levels were markedly increased in women with PCOS compared with levels observed in normal women. After FSH injection, PCOS women failed to demonstrate changes in circulating AMH over 24 h. A similar lack of alteration in serum AMH was observed in normal women.

CONCLUSIONS

These findings suggest that in PCOS and normal women, acute exposure to FSH does not appear to exert an effect on AMH production.

The effect of androgen blockade on granulosa cell estradiol production after follicle-stimulating hormone stimulation in women with polycystic ovary syndrome

CONTEXT

Previously, we have shown that women with polycystic ovary syndrome (PCOS) exhibit an exaggerated serum estradiol (E(2)) response to recombinant human FSH (rhFSH) (150 IU) compared with similarly treated normal women. This enhanced granulosa cell responsiveness is consistent with excessive follicular development after gonadotropin therapy and the corresponding risk of ovarian hyperstimulation syndrome. In vitro studies have shown that granulosa cells treated with androgens display greater FSH-induced E(2) production than untreated cells, suggesting a role for androgens in granulosa cell responsiveness.

MAIN OBJECTIVE

This study was conducted to determine whether blockade of androgen action in PCOS women by administration of the antiandrogen flutamide would alter E(2) responses to rhFSH.

DESIGN

We conducted a prospective cohort study.

SUBJECTS AND SETTING

We studied 11 women with PCOS at an institutional general clinical research center.

INTERVENTION

On study d 1, each subject received 150 IU rhFSH iv. Frequent blood samples were obtained over 24 h. After completion of rhFSH stimulation, each subject was treated with flutamide, 125 mg, twice daily, for 6 wk. Thereafter, the rhFSH stimulation test was repeated.

MAIN OUTCOME MEASURES

Baseline and stimulated E(2) levels before and after treatment were assayed.

RESULTS

Mean baseline and maximally stimulated E(2), integrated E(2) response, and fold change in E(2) were not different before and after treatment. Levels of testosterone, androstenedione, progesterone, 17-hydroxyprogesterone, estrone, and SHBG before and after treatment were unchanged. Baseline dehydroepiandrosterone sulfate levels declined significantly after flutamide therapy.

CONCLUSION

These findings indicate that in women with PCOS, the E(2) hyperresponsiveness to FSH may not be attributable to increased circulating androgens.

Comparison of follicle-stimulating-hormone-stimulated dimeric inhibin and estradiol responses as indicators of granulosa cell function in polycystic ovary syndrome and normal women

CONTEXT

Follicular phase secretion of inhibin B, like that of estradiol (E(2)), correlates with the quantity and quality of developing follicles. However, it has not been established whether inhibin B responses to gonadotropin stimulation parallel those of E(2) as a reflection of granulosa cell functional capacity.

OBJECTIVE

Our objective was to determine whether inhibin B responses to FSH stimulation are similar to those of E(2) in women with polycystic ovary syndrome (PCOS) and normal women.

DESIGN AND SETTING

We conducted a prospective study to compare ovarian responses in two groups of women at a general clinical research center in a tertiary academic medical center.

PATIENTS

Women with PCOS, 18-35 yr (n = 19), and normal ovulatory controls, 18-35 yr (n = 7), were recruited for study.

INTERVENTIONS

Serum samples were measured over a 24-h period after an iv injection of recombinant human FSH, 150 IU.

MAIN OUTCOME MEASURES

Serum E(2), inhibin A, and inhibin B responses after FSH administration were assessed.

RESULTS

In PCOS women, the 24-h production of inhibin B and E(2) after FSH was significantly greater than that of normal controls. Within the PCOS group, the fold change in inhibin B was significantly greater than that of E(2). Inhibin A responses between groups were similar and of markedly lower magnitude.

CONCLUSIONS

FSH-stimulated inhibin B responses may be employed to assess the functional capacity of granulosa cells in PCOS and normal women.

Luteinizing hormone secretion is not influenced by insulin infusion in women with polycystic ovary syndrome despite improved insulin sensitivity during pioglitazone treatment

It has been reported in women with polycystic ovary syndrome (PCOS) that LH secretion is not altered by insulin infusion. To determine whether insulin resistance may have precluded an effect of insulin, pulsatile LH secretion and gonadotropin responses to GnRH were examined in PCOS women (n = 9) before and after pioglitazone treatment (45 mg/d) for 20 wk in the presence and absence of a hyperinsulinemic euglycemic clamp (80 mU/m2.min). Frequent blood samples were obtained for 12 h (every 10 min) as well as during sequential administration of GnRH at doses of 2, 10, and 20 microg over 12 h. A significant (P < 0.05) improvement in insulin sensitivity was seen in the subjects after treatment. Mean LH levels, LH pulse frequency and amplitude, as well as gonadotropin responses to GnRH were not influenced by pioglitazone, either with or without insulin infusion. We conclude that in PCOS women, inappropriate gonadotropin release does not appear to be a consequence of hyperinsulinemia.

Relationship of GnRH-stimulated LH release to episodic LH secretion and baseline endocrine-metabolic measures in women with polycystic ovary syndrome

BACKGROUND AND OBJECTIVE

In polycystic ovary syndrome (PCOS) inappropriate gonadotrophin secretion is characterized by increased pulse frequency and amplitude, elevated 24-h mean serum concentrations, and greater responses to GnRH. While the mechanism(s) responsible for this increased release of LH are not well understood, enhanced LH secretion has been attributed to increased pituitary sensitivity to GnRH and feedback influences from circulating steroid hormones. To address these considerations, we conducted a study to examine the relationships between GnRH-stimulated LH responses, episodic gonadotrophin secretion, and baseline measurements of endocrine-metabolic function in PCOS.

PATIENTS

Serum LH responses to sequential multidose GnRH administration and pulsatile gonadotrophin secretion were examined in 13 PCOS and 13 normal women.

MEASUREMENTS

Serum LH, steroid hormone, insulin and glucose levels were determined in blood samples obtained during assessment of episodic gonadotrophin secretion and LH responses to GnRH stimulation.

DESIGN

Each subject was studied on two consecutive days. On study day 1 each subject underwent frequent blood sampling every 10 min for 12 h. On study day 2 each received sequential doses of GnRH, 2 microg, 10 microg and 20 microg, administered intravenously at 4-h intervals over a continuous 12-h period.

RESULTS

Serum LH responses following GnRH were markedly greater in PCOS compared to normal women, as expected. In individual PCOS, peak LH responses to GnRH were significantly correlated with corresponding basal LH and LH pulse amplitude, but not LH pulse frequency. In the PCOS group, LH responses were positively correlated with serum oestradiol (E2) and inversely related to body mass index (BMI). Between-group differences in LH responsiveness disappeared when controlling for serum testosterone (T) levels.

CONCLUSIONS

These results indicate that the absolute LH increment following GnRH is largely dependent on baseline LH levels and may account for the well-documented difference in LH responsiveness between PCOS and normal women. That neither LH responses to GnRH nor LH pulse amplitude were correlated to LH pulse frequency suggests involvement of other factors along with GnRH to account for increased LH secretion in PCOS. In addition to E2 and BMI, serum testosterone appears to be, at least in part, responsible for differences in LH secretion and release between PCOS and normal women.

Enhanced granulosa cell responsiveness to follicle-stimulating hormone during insulin infusion in women with polycystic ovary syndrome treated with pioglitazone

Women with polycystic ovary syndrome (PCOS) are known to exhibit insulin resistance with compensatory hyperinsulinemia. To determine the role of hyperinsulinemia on follicle function in PCOS, we examined 24-h estradiol (E(2)) responses to recombinant human FSH (r-hFSH), 75 IU, before and during insulin infusion both before and after administration of pioglitazone (30 mg/d) in seven PCOS women. Each subject underwent two 10-h hyperinsulinemic-euglycemic clamps at rates of 30 (low dose) and 200 (high dose) mU/m(2).min, respectively. During both low- and high-dose insulin infusions, E(2) responses to r-hFSH were unaltered compared with that observed in the absence of insulin. Pioglitazone administration for 5 months improved insulin sensitivity as indicated by significantly (P < 0.05) increased glucose infusion rates during the clamp studies. At 3 months of treatment, r-hFSH-stimulated E(2) responses were not different from those observed before treatment. With pioglitazone treatment, E(2) responses to r-hFSH remained unchanged during low-dose insulin infusion, whereas a highly significant (P < 0.02) increased response was noted with the high-dose hyperinsulinemic-euglycemic clamp. In addition to a greater magnitude of response, peak levels of E(2) were sustained longer compared with that seen before treatment. The data indicate that granulosa cell responsiveness to FSH was enhanced by insulin after improved insulin sensitivity induced by pioglitazone. These findings are consistent with the possibility that PCOS granulosa cells are insulin resistant.

Increased luteinizing hormone secretion in women with polycystic ovary syndrome is unaltered by prolonged insulin infusion

In PCOS women with insulin resistance, hyperinsulinemia may contribute to inappropriate gonadotropin secretion. To determine whether insulin influences gonadotropin release in PCOS, pulsatile LH secretion and gonadotropin responses to GnRH were evaluated before (phase 1) and during (phase 2) insulin infusion. In phase 1, 11 PCOS and 9 normal women on separate days underwent 1) frequent blood sampling (q 10 min) for 12 h and 2) gonadotropin stimulation by successive doses of GnRH, 2 microg, 10 microg, and 20 microg, administered i.v. at 4 h intervals over a continuous 12 h. In phase 2, studies were repeated 2 h after initiation of a 12-h hyperinsulinemic-euglycemic clamp (80 mU/m(2).min). Administration of insulin to both groups failed to alter mean serum gonadotropin concentrations, LH pulse frequency, or LH pulse amplitude. Moreover, gonadotropin responses to GnRH were unchanged by insulin infusion. In PCOS and normal women, a significant reduction of serum androstenedione was associated with insulin administration, whereas no differences were noted for the remaining androgens and estrogens measured. These findings demonstrated that in PCOS women, LH secretion and gonadotropin responses to GnRH were not influenced by insulin administration. Insulin infusion had little effect on steroid hormone production with the possible exception of androstenedione. These results suggest that inappropriate LH secretion in PCOS is not a direct consequence of insulin resistance and compensatory hyperinsulinemia.

Evidence for abnormal granulosa cell responsiveness to follicle-stimulating hormone in women with polycystic ovary syndrome

Women with polycystic ovary syndrome (PCOS) undergoing ovulation induction appear to be extremely sensitive to gonadotropin stimulation and at increased risk for ovarian hyperstimulation syndrome. To determine granulosa cell responsiveness to recombinant human FSH (r-hFSH), dose-response studies were conducted in 16 individual PCOS patients and 7 normal women. Each subject received an iv injection of r-hFSH at doses of 0, 37.5, 75, or 150 IU in a randomized fashion on four separate occasions. Blood samples were obtained at frequent intervals before and for 24 h after r-hFSH administration for measurement of gonadotropins and steroid hormones. Our results showed that administration of r-hFSH produced instantaneous and equivalent dose-related increases in serum FSH in PCOS and normal women, which were followed by similar exponential decreases to baseline levels within 24 h in both groups. In PCOS subjects, the peak mean incremental response of serum estradiol (E(2)) to 150 IU of r-hFSH was 1.8-fold greater (P < 0.0001) and considerably accelerated compared with that found in normal women. In contrast, E(2) responses to 37.5 IU and 75 IU were similar between groups. Regression analysis of maximal E(2) concentrations in response to r-hFSH in each individual subject revealed that the slope of the linear trend line in the group of women with PCOS (r = 0.82) was significantly greater (P < 0.01) than that of normal controls (r = 0.71). The time-course of response revealed that in PCOS women, increases of E(2) were not sustained, compared with those of normal controls, because peak concentrations were followed by an estimated 40% decrement in circulating levels, whereas E(2) levels in normal women persisted for 24 h after reaching maximal values. These findings indicate that women with PCOS exhibit a significantly greater capacity for E(2) production in response to iv r-hFSH, compared with normal women. In PCOS, E(2) production was relatively transient because after peak concentrations a marked decline was detected at each dose, unlike normal women who exhibited persistent elevations of E(2) for up to 24 h. That this distinction was dose-dependent supports the concept of an FSH dose-response threshold, beyond which PCOS but not normal women are susceptible to ovarian hyperresponsiveness.