Hirsutism is characterized by excessive growth of terminal hair in a male pattern. Idiopathic hirsutism (IH) is a common cause of hirsutism. Since there are few data demonstrating IH is associated with insulin resistance, we tried to assess various insulin sensitivity indices in lean IH and compare with healthy subjects. A cross-sectional study was performed in 71 lean (BMI between 20-25 kg/m²) women (17-39 years old), 31 with IH and 40 healthy individuals. Blood glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), hepatic insulin sensitivity (ISI _HOMA), Quicky index, reciprocal fasting insulin resistance index, fasting Belfiore index, and fasting glucose/insulin ration (GIR) were estimated using a single fasting sample of glucose and insulin levels. Raynaud indices calculated using the mathematical estimation in a single fasting sample of insulin levels were determined and compared in two groups. Fasting insulin, Raynaud index, HOMA-IR and Fasting insulin resistance index (FIRI) results were higher in IH group than in controls (p<0.01, for all). Fasting Belfiore index, QUICKI index, ISI _HOMA and FIRI^-1 results were lower in IH group than in controls (p<0.01, for all). Our study showed that lean IH patients were more insulin resistant than healthy subjects. We propose that insulin sensitivity indices are useful methods for measuring insulin resistance in IH.