The investigators are doing this research study to look at how the medication metformin affects the cells in the body of patients with PCOS. Specifically, the investigators will look at how metformin affects the mitochondria. Mitochondria are the part of cells that produce fuel (energy) for other cells and play a role in metabolism. The investigators would like to see whether there is a relationship between mitochondrial activity and symptoms of polycystic ovary syndrome (PCOS) before and after treatment with metformin. They would also like to study whether genes affect the response to metformin in women with PCOS.