To examine inhibin-F activity (FSH-suppressing activity) in human follicular fluid of polycystic ovary (PCO) patients, 13 follicles from 5 documented PCO patients and an additional 31 follicles from normal women in the follicular phase of the menstrual cycle were sampled, and inhibin-F activity was measured in rat anterior pituitary cell cultures. Inhibin-F activity was measured in follicular fluid after stripping steroids from the fluids using treatment with dextran and activated charcoal. Estrogen, progesterone, and Δ⁴-androstenedione in the follicular fluid were also determined by RIA. Estrogen and progesterone levels in follicular fluid from PCO follicles 3.9 ± 0.34 mm in diameter were comparable with those in follicular fluid obtained from viable follicles (which had a Δ⁴- androstenedione to estrogen ratio of 10 or less) from normal women. Δ⁴-Androstenedione levels in PCO follicles were higher (P < 0.01) than those in viable and atretic follicles of normal women. Inhibin-F levels in PCO follicles were comparable to those in viable follicles, but significantly greater (P < 0.01) than levels in atretic follicles of normal women. If inhibin-F levels in both atretic and viable follicles of normal women were pooled, the levels were less {P < 0.05) compared to the level in PCO follicular fluid. As an additional control, follicular fluid was collected from 90 follicles of normal women throughout the menstrual cycle, and follicular size was determined as well as inhibin-F and steroid content. Small follicles <8 mm; (comparable in size to the PCO follicles examined) obtained at each stage represented 79%, 24%, 0%, and 94% of the total follicles obtained in the early to midfollicular, late follicular, preovulatory, and luteal phases of the cycle, respectively. Inhibin-F activity in the fluids of these follicles was less than that in PCO follicular fluid. The average inhibin content of all of the small normal follicles was 197 ± 34 U/10 μl, which was significantly less (P < 0.05) than the level in PCO follicles (332 ± 13 U/10 μl). These data represent the first observation of inhibin-F activity in PCO follicular fluid and suggest the possibility of involvement of inhibin-F in bringing about low or normal basal levels of FSH in the presence of elevated basal LH levels often observed in PCO patients.

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