Inclusion Criteria:

• Obese (≥ 30 kg/m2) premenopausal women with PCOS and normal women between 18-40 years of age.

• PCOS women only:

  • oligomenorrhea (<= 8 menstrual periods annually),
  • biochemical hyperandrogenemia (elevated total or free testosterone),
  • normal thyroid function tests and serum prolactin, and
  • exclusion of 21alpha-hydroxylase deficiency by a fasting 17alpha-hydroxyprogesterone <200 ng/dl.

• Normal women only:

  • regular monthly menses, and
  • normal serum total and free testosterone.

• All women:

  • acceptable health on the basis of interview, medical history, physical examination, and laboratory tests (CBC, SMA20, urinalysis),
  • have not been dieting in the 3 months prior to study enrollment,
  • signed, witnessed informed consent,
  • ability to comply with study requirements.

Exclusion Criteria:

• Diabetes mellitus by fasting glucose or OGTT, or clinically significant pulmonary, cardiac, renal, hepatic, neurologic, psychiatric, infectious, neoplastic and malignant disease (other than non-melanoma skin cancer).
• Documented or suspected recent (within one year) history of drug abuse or alcoholism.
• Ingestion of any investigational drug within 3 months prior to study onset.
• Pregnancy as documented by urine hCG.
• PCOS women only: Change in PCOS medication regimen (oral contraceptives, spironolactone, insulin sensitizers) within 3 months prior to the start of the study.

• Normal women only:

  • history of gestational diabetes,
  • positive family history for first-degree relative with diabetes,
  • disorders linked to insulin resistance (hypertension or dyslipidemia),
  • Use of oral or other systemic contraceptives, or spironolactone within 3 months prior to the start of the study,
  • Use of medications (including OTC drugs) known to affect insulin sensitivity such as metformin, rosiglitazone, pioglitazone, niacin, corticosteroids, beta blockers, calcium channel blockers and thiazide diuretics within 3 months prior to the start of the study.