β-cell function:: A key pathological determinant in polycystic ovary syndrome

We report data from 60 patients with polycystic ovary syndrome ( PCOS) who had undergone assessment of insulin resistance, pancreatic beta-cell function, obesity, and androgen levels to elucidate the complex relationships among these traits. Homeostasis model assessment was used to quantify insulin resistance and beta-cell function. A reference population was derived from the National Health and Nutrition Examination Study ( NHANES III, 1988 - 1994). Indices of insulin resistance, insulin secretion, bioavailable testosterone, and body mass index all exhibited significant pairwise correlations. Multiple regression analysis clarified the phenotypic relationships, demonstrating that insulin resistance and bioavailable testosterone were independent predictors of beta-cell function; beta-cell function and obesity were independent predictors of insulin resistance; and beta-cell function was an independent predictor of bioavailable testosterone. Of note, comparison with normal women from NHANES revealed a significantly stronger relationship between beta-cell function and insulin resistance in PCOS, raising the possibility of an intrinsic defect in beta-cell function whereby increasing insulin resistance leads to a greater insulin response in PCOS than normal. The altered relationship of beta-cell function and insulin resistance coupled with the fact that beta-cell function, not insulin resistance, was a predictor of hyperandrogenemia suggests that beta-cell dysfunction may be a key pathogenic determinant in PCOS.