Polycystic ovary syndrome (PCOS) is a medical condition that has brought multiple specialists together. Gynecologists, endocrinologists, cardiologists, pediatricians, and dermatologists are all concerned with PCOS patients and share research data and design clinical trials to learn more about the syndrome. Insulin resistance is a common feature of PCOS and is more marked in obese women, suggesting that PCOS and obesity have a synergistic effect on the magnitude of the insulin disorder. It leads to increased insulin secretion by beta-cells and compensatory hyperinsulinemia. Hyperinsulinemia associated with insulin resistance has been causally linked to all features of the syndrome, such as hyperandrogenism, reproductive disorders, acne, hirsutism and metabolic disturbances. If beta-cell compensatory response declines, relative or absolute insulin insufficiency develops which may lead to glucose intolerance and type 2 diabetes. Moreover, insulin resistance in PCOS may be considered a risk factor for gestational diabetes (GD).