The goal of this research study is to study the effect of testosterone or estrogen on blood sugar control and fat metabolism. Changes in hormone levels with age may affect risk factors for heart disease such as diabetes. Diabetes is a glandular condition associated with lack of the hormone insulin or an insensitivity to it resulting in problems with blood sugar control and fat metabolism. The effect of commonly used hormonal supplements such as testosterone by older adults on insulin and body composition is not well understood. In this study, the role of testosterone and estrogen on your ability to control blood sugar and your body composition will be assessed.

The investigators plan to study 60 subjects. All of these subjects will be healthy older men between the ages of 60-85 years old who are not on testosterone therapy. Subjects that are screened who have any clinically significant abnormalities detected on their screening physical exam or laboratory testing (e.g. Prostate Specific Antigen > 4), who have a history of prostate cancer, polycythemia, or who cannot take testosterone will not be included.

If a subject is eligible to participate after initial screening, that subject will take medications to adjust their hormone levels and have tests performed that measure insulin sensitivity and adiposity before and after these hormone medications. The outcomes that will be measured are: 1) insulin sensitivity, 2) hormone levels (total and free testosterone levels, sex hormone-binding globulin levels) and 3) body composition and abdominal adiposity.

Inclusion Criteria:

• males age 60-85 years
• non-diabetic fasting glucose and 2-hour oral glucose tolerance test (OGTT)
• overall good general medical health and signed informed consent
• willing to travel to West Los Angeles VA and University of California, Los Angeles in Los Angeles, California

Exclusion Criteria:

• any clinically significant abnormalities detected on screening physical exam or laboratory testing (e.g. prostate specific antigen > 4)
• or other symptom or history of a significant underlying medical or psychiatric illness
• BMI < 20 or > 40
• subjects already on testosterone therapy or medications that might influence glucose regulation or hormone levels
• subjects with a history of deep venous thromboses, pulmonary embolism, breast cancer, prostate cancer, polycythemia or other contraindications to estrogen or testosterone

Small sample size may limit generalizability of these results. Follow-up studies are being conducted to further evaluate these results.