Its cause remains not fully understood. PCOS is characterized by hyperandrogenism, chronic anovulation and / or polycystic ovaries. Patients, in a high percentage of cases show obesity, hirsutism, acne, menstrual irregularities and infertility. Clinically and biologically PCOS is a heterogeneous disorder with a not yet clear pathogenesis. Therefore, discussions on its definition and diagnosis still subsist. Seventy years ago Stein and Leventhal published their findings in 7 women with amenorrhea, hirsutism, acne, obesity and polycystic appearance of their ovaries. Since then, diagnostic criteria for PCOS suffered multiple modifications.