This study provided 198 healthy men 20 to 50 years of age with goserelin acetate (to suppress endogenous testosterone and estradiol) and randomly assigned them to receive a placebo gel or 1.25g, 2.5g, 5g, or 10g of testosterone gel daily for 16 weeks. Another 202 healthy men received goserelin acetate, placebo gel or testosterone gel, and anastrozole (to suppress the conversion of testosterone to estradiol). Changes in the percentage of body fat and in lean mass were the primary outcomes. Subcutaneous- and intraab- dominal-fat areas, thigh-muscle area and strength, and sexual function were also assessed. The results showed that the percentage of body fat increased in groups receiving placebo of 1.25g or 2.5g of testosterone daily without anastrozole (mean testosterone level, 44±13 ng per deciliter, 191±78 ng per deciliter, and 337±173 ng per deciliter, respectively). Lean mass and thigh-muscle area decreased in men receiving placebo and in those receiving 1.25g of testosterone daily without anastrozole. Leg-press strength fell only with placebo administration. In general, sexual desire declined as the testosterone dose was reduced. The authors conclude that the amount of testosterone required to maintain lean mass, fat mass, strength, and sexual function varied widely in men. N Engl J Med. 2013 September. PMID: 24024838
