Inclusion Criteria:

1. Acceptable health based on interview, medical history, physical examination, and laboratory tests (SMA20 and CBC);
2. Have not taken OCs in the past 3 months;
3. Ability to comply with the requirements of the study;

4. Ability and willingness to provide signed, witnessed informed consent. In addition, women with the metabolic syndrome must meet the National Cholesterol Education Program (NCEP) defined criteria of the metabolic syndrome, that is, having at least 3 of the 5 factors:

   1. increased waist circumference > 35 inches,
   2. hypertriglyceridemia ≥ 150 mg/dL,
   3. low HDL cholesterol < 50 mg/dL in women,
   4. hypertension (≥ 130/≥ 85 mmHg),
   5. fasting glucose ≥ 100 mg/dL.

Obese women with or without the metabolic syndrome should have a BMI > 30 kg/m2 and lean women should have a BMI < 25 kg/m2.

Exclusion Criteria:

1. Diabetes mellitus by fasting glucose or a 2-hour oral glucose tolerance test (OGTT);
2. Clinically significant pulmonary, cardiac (including but not limited to ischemic heart disease, stable/unstable angina, and congestive heart failure), renal, hepatic, cholestatic, neurologic, psychiatric, infectious, and malignant disease (other than melanoma skin cancer);
3. History of thromboembolism, myocardial infarction, cerebrovascular accident, vascular disease, known coagulopathy, prolonged immobilization, or recent major surgery (within past 6 months);
4. Systolic blood pressure greater than 160 mmHg or diastolic blood pressure greater than 100 mmHg (mild hypertension is not an exclusion criterion);
5. History of breast cancer, migraine headaches, or age ≥ 35 years and smoker of ≥ 20 cigarettes/day;
6. Use of metformin, thiazolidinediones, anti-hyperlipidemic drugs, anti-hypertensive drugs, glucocorticoids, or anti-androgens (spironolactone, flutamide, etc.) within 3 months;
7. Documented or suspected illicit drug abuse or alcoholism within one year;
8. Ingestion of any investigational drugs within 3 months prior to the study onset; and
9. Pregnancy or lactation (≤ 6 weeks postpartum);
10. Hematocrit < 33g/dL. These exclusion criteria are based on study requirements and also go beyond guidelines for OC use published by the World Health Organization.