Insulin action in the normal and polycystic ovary

Insulin stimulates steroidogenesis by granulosa cells of normal and polycys tic ovaries and interacts with gonadotropins in an additive or, as in the c ase of LH, a synergistic manner. These actions appear to be mediated specif ically by the insulin receptor rather than by cross-reaction with the type- I IGF receptor, even in tissue obtained from PCOS women with biochemical ev idence of insulin resistance. This article suggests that hyperinsulinemia m akes a significant contribution to premature arrest of follicle growth, whi ch is characteristic of anovulation in women with PCOS, and that the intera ction of insulin with LH is a key element in this process. Insulin also may have a role in amplifying LH-induced androgen production by theca cells, w hich may help to explain the prominence of symptoms of hyperandrogenism in obese patients with PCOS.