There are a number of variants that have been determined to be associated with PCOS risk. The investigators will determine the effect of these variants on the phenotype and response to treatment in PCOS. Subjects with PCOS will undergo extensive phenotyping including adipose tissue biopsy, dual energy X-ray absorptiometry (DXA, bone density) scan to examine adipose stores, an intravenous glucose tolerance test to study insulin sensitivity and beta cell function, androgen stimulation and inflammatory markers. The phenotyping will be repeated after 3 months of treatment with metformin. The studies will determine whether the genotype at PCOS risk variants dictates phenotype and response to treatment with metformin. Discovering genes involved in the etiology of PCOS will help pull us out of the endless circle that has characterized our understanding of PCOS pathophysiology for many years. The proposal also has the potential to illuminate one etiology of insulin resistance, which is present even in lean women with PCOS, and the impaired glucose tolerance and diabetes found in over 40% of PCOS patients.