INHIBIN-A AND INHIBIN-B IN WOMEN WITH POLYCYSTIC OVARIAN SYNDROME DURING TREATMENT WITH FSH TO INDUCE MONO-OVULATION

OBJECTIVE Polycystic ovary syndrome (PCOS) is characterized by the pre sence of numerous small antral follicles arrested at a diameter of les s than 10 mm, As development of large antral follicle(s) can be stimul ated by the administration of FSH, it has been suggested that the arre st of follicle development is due to a relative lack of or resistance to FSH. We have measured the concentration of FSH and LH and the ovari an hormones oestradiol, inhibin A and B, in relation to the dynamics o f follicular development in women with PCOS under basal conditions and during treatment with FSH, DESIGN The concentrations of FSH, LH, oest radiol, inhibin A and B were measured in women with PCOS who were untr eated (n = 9) or following progesterone-induced menses (10 cycles in s ix women) and control women on day 3 of a normal cycle (n=10), Serial measurements of the same hormones were made during induction of ovulat ion with low dose of exogenous FSH in the women with PCOS who had been treated with progesterone, The dynamics of follicle development were measured by serial pelvic ultrasound examinations during treatment wit h FSH in PCOS and in the follicular phase of control cycles. PATIENTS Nine anovulatory untreated women with PCOS were compared with 10 norma l women and six women with PCOS undergoing FSH treatment. RESULTS The concentrations of inhibin B and LH were higher in both groups of women with PCOS than in normal control women on day 3, In untreated women w ith PCOS the concentration of inhibin A was also significantly elevate d compared to control women (P<0.01) but not in women pretreated with progesterone, Basal concentrations of oestradiol were also significant ly higher in women with PCOS than in the early follicular phase of the normal cycle. There were no significant differences in the concentrat ion of FSH between the groups. Treatment of women with PCOS with low d oses of FSH stimulated the development of a single dominant follicle w hich had an identical rate of growth and secretion of oestradiol and i nhibin A to that observed in spontaneous cycles in normal women. In co ntrast to normal women, the concentration of inhibin B rose 7-fold fol lowing FSH treatment and remained elevated until the luteal phase. CON CLUSIONS The raised concentrations of inhibin A and B in women with PC OS probably reflects the increased number of small antral follicles ch aracteristically present in that condition. The striking similarity in the dynamics of growth of the dominant follicle and the pattern in co ncentration of oestradiol and inhibin A in normal women and in women w ith PCOS treated with modest amounts of FSH, suggests that the arrest of follicle development in PCOS may be due to a relative deficiency of FSH which may in turn be secondary to increased secretion of either o r both inhibin forms.