SERUM ALPHA-INHIBIN LEVELS IN POLYCYSTIC-OVARY-SYNDROME - RELATIONSHIP TO THE SERUM ANDROSTENEDIONE LEVEL

To date, only one study has demonstrated increased serum inhibin level s in women with polycystic ovary syndrome (PCOS). Moreover, no relatio nship between serum inhibin and either FSH or androgen levels has been noted. This lack of data could be due to 1) the heterogeneity of PCOS and the small sample size of previous studies, and/or 2) the complexi ty of circulating inhibin molecular forms, which hinders the precise e valuation of bioactive inhibin. In the present study, alpha-inhibin le vels were assayed in the serum of 61 healthy women and 72 PCOS patient s by means of an alpha-alpha enzyme-linked immunosorbent assay. Serum alpha-inhibin levels together with LH and androstenedione (A) levels w ere significantly increased in PCOS women (mean +/- SD, 1.45 +/- 0.55 vs. 0.94 +/- 0.36 U/mL in controls; P < 0.001). Moreover, simple and p artial regression analysis demonstrated that serum A levels were posit ively and independently correlated to serum alpha-inhibin (r = 0.32; P < 0.01) and LH levels (r = 0.48; P < 0.001) in PCOS. The respective i nfluences of alpha-inhibin and LH on A variability were 20% and 80%, a s determined by multiple regression analysis. In conclusion, in agreem ent with recent in vitro data, our in vivo results argue for a role of inhibin in the hyperandrogenism of PCOS together with, but independen tly from, that of LH. Further studies are needed to determine whether this effect is produced by inhibin A and/or B.