Inhibin A, inhibin B and activin A concentrations in follicular fluid from women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is characterized by arrested follicle development at the early antral stage. Alterations in inhibin production by developing follicles could be involved in PCOS by suppressing follicle stimulating hormone concentrations during the follicular phase of the menstrual cycle as well as by increasing thecal androgen production. Inhibin B appears to be more important than inhibin A during the follicular phase; however, there are no data regarding the follicular fluid concentrations of inhibin B in PCOS. The purpose of this study was to compare inhibin A, inhibin B and activin A concentrations in the follicular fluid from regularly cycling women and women with PCOS. Inhibin A, inhibin B and activin A were measured in the follicular fluid of 4-7 mm follicles from PCOS ovaries and size-matched follicles from normally cycling women by specific and sensitive two-site enzyme-linked immunosorbent assays. In both control and polycystic ovaries, inhibin B was approximately 10-fold higher than activin A and more than 100-fold higher than inhibin A. There was no difference in activin A concentrations between PCOS and control follicles. In control ovaries, the inhibin B and inhibin A concentrations in dominant follicles were significantly higher than in cohort follicles. While inhibin A concentrations were lower in PCOS follicles than in normal cohort follicles, there was no difference in inhibin B concentrations between PCOS follicles and normal cohort follicles. These data are consistent with the concept that inhibin B is the physiologically most important form of inhibin during the follicular phase of the menstrual cycle and indicate that PCOS is not associated with increased inhibin B concentrations in follicular fluid.