Objective: --To study the changes in body composition produced by large doses of testosterone and reversal of changes when the drug is discontinued.
Design: --Weekly injections of testosterone enanthate were given to young adult male volunteers for 12 weeks. Repeated assays of lean body mass (LBM) by potassium 40 counting were made during this period and at intervals during the ensuing 5 to 6 months.
Participants and setting: --Subjects who were living on their own, who were known to be free of significant disease, and who volunteered as controls for a study of patients with neuromuscular disease. Assays were done in the Clinical Research Center.
Main outcome measures: --Changes in body weight, LBM, and (by subtraction) body fat.
Results: --Testosterone treatment produced a progressive increase in LBM and a progressive decrease in body fat. Body composition reverted slowly toward normal when the injections were stopped; thus, the effects of testosterone lingered for some time. The magnitude of the observed changes in LBM was in keeping with the change in urinary creatinine excretion reported for these same subjects.
Conclusion: --Testosterone is a powerful anabolic agent that also serves to reduce body fat content.