Additional Study Information: Polycystic ovary syndrome (PCOS) is a common disorder. Young women with PCOS have irregular or absence of menstruation and excessive acne and or hair on their bodies. They may have multiple cysts on their ovaries. Adolescents and women affected with PCOS are at risk of developing abnormalities in their blood including high fat, low HDL cholesterol (good cholesterol), high blood pressure and prediabetes or diabetes; they also have increased fat in the abdominal area. This cluster of abnormalities is called the metabolic syndrome. Currently, there are no established markers to identify which adolescents or young adults with PCOS who may develop the metabolic syndrome. Specific body fat distribution patterns, fat in muscles the liver and pancreas are associated with metabolic abnormalities. Young women with PCOS also may have lower bone mineral density than unaffected young women. This has never, to our knowledge, been investigated in adolescents with PCOS. Some young women with PCOS have insulin resistance. This means that their body needs to produce more insulin in order to keep their blood sugar at a normal level. Early signs of insulin resistance include accumulation of fat in the muscle, liver, pancreas and trunk. Metformin is a medication that is used to treat insulin resistance in adolescents withPCOS. After participation in the baseline study, adolescents and young women who are identified to have PCOS and elevated liver fat will be randomized to intervention with metformin or placebo for 6 months and will sign another consent form in order to participate in the intervention portion of the study (AAAF4452). These subjects will all have an interval check-up visit at three months. The purpose of this study is to see if young women with insulin resistance and PCOS who are treated with metformin for six months have a decline in accumulation of fat in the muscle, liver and trunk and an improvement in their oral glucose tolerance testing.