The investigator's global hypothesis is that women with Polycystic Ovary Syndrome (PCOS) can be separated into subtypes based on their response to metformin. The investigators propose here to use both targeted and non-targeted metabolomic approach to identify pathways associated with metformin's effect on insulin sensitivity and endothelial function. This pilot project will be the foundation for developing tailored therapeutic approaches to Polycystic Ovary Syndrome and identifying novel drug targets.

The investigators propose to use both targeted and non-targeted metabolomic approaches to identify pathways associated with metformin's effect on insulin sensitivity, weight, androgens and endothelial function. This project will be the foundation for developing tailored therapeutic approaches to Polycystic Ovary Syndrome and identifying novel drug targets. This pilot project is intended to inform the development of hypothesis and specific aims for a future grant application to National Institutes of Health (NIH).

Inclusion Criteria:

• Body mass index (BMI) greater than or equal to 25
• Polycystic Ovary Syndrome criteria of both oligomenorrhea (<9 menses per year) and androgen excess [clinical hirsutism (Ferriman-Gallway score >8 or severe acne) or elevated testosterone].
• Taking no medications for the treatment of insulin resistance.

Exclusion Criteria:

• Diagnosis of Cushing's syndrome
• Untreated hypo/hyperthyroidism
• Elevated prolactin
• Congenital adrenal hyperplasia
• Renal insufficiency (creatinine > 1.5)
• Diabetes
• Medications that can significantly affect endothelial function
• Pregnancy
• Breast Feeding
• Taking oral contraceptives
• Currently smoking