Polycystic ovary syndrome is the most common endocrine disorder among women of reproductive age, probably as a result of interaction between ovarian genetic traits and many congenital or environmental factors, which usually becomes manifest during adolescence. The most common postnatal contributor is obesity, but the fundamental defect seems to be an intrinsic disorder in the intraovarian regulation of steroidogenesis in response to luteinizing hormone, often accompanied by selective insulin resistance, in which muscle is insulinresistant, while the ovaries, adrenals and adipose tissue remain relatively sensitive, promoting androgen production and obesity. The syndrome is clinically characterized by oligoamenorrhea, menstrual dysfunction, infertility, hyperandrogenism, as well as the frequent presence of associated risk factors for cardiovascular disease and diabetes, including obesity, insulin resistance, glucose intolerance and dyslipidemia. Other possible clinical manifestations include obstructive sleep apnea, nonalcoholic fatty liver disease, mood or eating disorders. The evaluation begins with a clinical evaluation of hirsutism and menstrual abnormality, followed by laboratory testing and transvaginal ultrasonography. Once a diagnosis has been established, it is important to identify and monitor the main features of metabolic syndrome and the risk for complications. Weight loss can restore ovulatory cycles and improve metabolic risk, so it is the first-line intervention for most women. Oral contraceptives are the main pharmacologic therapy for managing hyperandrogenism and menstrual dysfunction, but sometimes antiandrogen has to be added. Although treatment of type 2 diabetes mellitus is the only approved indication for metformin, it has been used ''offlabel'' to treat or prevent several clinical problems associated with polycystic ovary syndrome, such as obesity, type 2 diabetes mellitus, infertility, oligomenorrhea, hirsutism.