Muscle and Fat On and Off Testosterone Injections

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Nelson Vergel

Sequence of Changes in Body Composition Induced by Testosterone and Reversal of Changes after Drug Is Stopped

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.

Forbes GB, Porta CR, Herr BE, Griggs RC. Sequence of Changes in Body Composition Induced by Testosterone and Reversal of Changes After Drug Is Stopped. JAMA.1992;267(3):397-399.

Dosing Schedule: Five subjects were given 0.75 mg of testosterone enanthate per kilogram of body weight daily for 4 days intramuscularly; all seven subjects then received approximately 3 mg/kg each week for a total of 12 weeks. The average cumulative dose was 42 mg/kg, with a range of 39 to 49 mg/kg.

Note: For a 170 Lbs man, 0.75 mg/Kg translates into 58 mg per day for 4 days, then 230 mg per week for 12 weeks. So this dose is somewhat higher than the dose usually used in testosterone replacement (200 mg per week max). 7 Kg (15.5 Lbs) of lean body mass were gained and 3.5 Kg (7.7 Lbs) of fat were lost in 12 weeks. The study did not mention if subject exercised.

Time course of weight (W) change (dotted lines), lean body mass (LBM) change (solid lines), and body fat change (dashed lines) in response to testosterone administration and following cessation of drug.

Time zero for the latter was taken as 21 days after the last testosterone injection. Data given are means ±SEM; number of subjects is shown in parentheses. Statistical significance was determined by one-tailed t tests. Horizontal lines at bottom of Figure indicate mean assay intervals ±SEM; asterisks, P<.05; daggers, P<.01 ; and double dagger, P<.001.


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