Raised insulin levels are now recognized as a feature of PCOD, and hyperinsulinemia has been shown to contribute to ovarian over production of androgen. Insulin-lowering therapies, such as metformin, can bring about improvements in insulin resistance and ovarian hyperandrogenism. Metformin reduces plasma levels of LH, hyperinsulinism and ovarian level of androgens. This is the rational basis for its use in the treatment of PCOS.