Dose-Response of Gonadal Steroids and Bone Turnover in Older Men

In this protocol, men age 60-75 will be randomized to one of 6 groups. Groups 1-5 will receive goserelin acetate (Zoladex) plus 0 (placebo gel), 1.25, 2.5, 5, or 10\* g/day of testosterone gel (Androgel). Group 6 will receive placebos for both goserelin acetate and testosterone gel. (\*Note that the 10 g/day dose was reduced to 7.5 g/day part-way through the trial due to reports of possible increased risk of cardiovascular events with testosterone administration). Subjects will be blinded with respect to group assignment. Dietary calcium intake will be assessed by a research dietitian and adjustments made through diet or supplements so that calcium intake is between 1000 and 1200 mg/day. Subjects will be seen on the Clinical Research Center at 4 week intervals for 16 weeks (0, 4, 8, 12, and 16 weeks). At each visit, compliance with Androgel will be assessed by reviewing a medication diary. A standardized series of questions will be posed to each subject to assess potential side effects of the study drugs. Subjects receiving Androgel' will be given a new 4 week supply of medication (except at week 16). A fasting blood and second voided urine sample will be collected. After the blood and urine samples have been obtained, subjects will be given their goserelin injection. The blood and urine tests listed below as well as anthropometric measures, and questionnaires will be performed at each visit. Dual-energy x-ray absorptiometry (DXA), quantitate computed tomography (QCT) scans, and strength assessments will be performed at 0 and 16 weeks only. Subjects who discontinue participation at or after week 8 will be asked if they are willing to have an early discontinuation visit in which all procedures normally done at week 16 will be performed. The following measures will be assessed: * Routine chemistries and prostate specific antigen, PSA (for safety assessment) * Bone turnover using blood and urine tests * Hormones * Lipids * Body composition * Strength * Sexual desire and erectile function * Bone mineral density and bone microarchitecture