Serum alpha-inhibin levels in polycystic ovary syndrome: relationship to the serum androstenedione level.

Abstract

To date, only one study has demonstrated increased serum inhibin levels in women with polycystic ovary syndrome (PCOS). Moreover, no relationship 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 complexity of circulating inhibin molecular forms, which hinders the precise evaluation of bioactive inhibin. In the present study, alpha-inhibin levels were assayed in the serum of 61 healthy women and 72 PCOS patients by means of an alpha-alpha enzyme-linked immunosorbent assay. Serum alpha-inhibin levels together with LH and androstenedione (A) levels were 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 partial regression analysis demonstrated that serum A levels were positively 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 influences of alpha-inhibin and LH on A variability were 20% and 80%, as determined by multiple regression analysis. In conclusion, in agreement with recent in vitro data, our in vivo results argue for a role of inhibin in the hyperandrogenism of PCOS together with, but independently from, that of LH. Further studies are needed to determine whether this effect is produced by inhibin A and/or B.