Although estimates vary, about 30%-80% of women with PCOS have insulin resistance.
Hyperinsulinemia (high blood insulin levels) produces hyperandrogenism (excessive levels of male hormones such as testosterone) by stimulating ovarian androgen production and by reducing serum sex-hormone binding globulin (SHBG). This can heighten PCOS symptoms.
The hormone insulin is primarily known for its role in glucose regulation. Under normal circumstances, insulin assures the efficient transfer of glucose from the bloodstream to the body. Insulin also serves as a signal to the liver to begin or discontinue glucose production.
If the level of glucose in the cells is sufficient, insulin levels drop, signaling the liver to slow down glucose production. In contrast, if the cells of the body are not receiving enough glucose, the level of insulin will rise, signaling the liver to produce greater amounts of glucose.
Insulin resistance (also known as Syndrome X) is the inability of insulin to perform its job effectively in the body. In early stages of Syndrome X, the body simply compensates by causing the beta cells of the pancreas to produce more insulin. Ultimately in some women, however, the beta cells may wear out and the body ceases to produce insulin in the amounts needed. The resultant condition is Type II diabetes mellitus.