Changes in muscle mass, muscle strength, and power but not physical function are related to testosterone dose in healthy older men.

Objectives: To examine the effect of graded doses of testosterone on physical function and muscle performance in healthy, older men.

Design: Randomized, double-blind, placebo-controlled clinical trial.

Setting: General clinical research center.

Older men are as responsive as young men to the anabolic effects of graded doses of testosterone on the skeletal muscle.

Although testosterone levels and muscle mass decline with age, many older men have serum testosterone level in the normal range, leading to speculation about whether older men are less sensitive to testosterone. We determined the responsiveness of androgen-dependent outcomes to graded testosterone doses in older men and compared it to that in young men. The participants in this randomized, double-blind trial were 60 ambulatory, healthy, older men, 60-75 yr of age, who had normal serum testosterone levels.

Testosterone dose-dependently increases maximal voluntary strength and leg power, but does not affect fatigability or specific tension.

Testosterone supplementation in men increases fat-free mass, but whether measures of muscle performance, such as maximal voluntary strength, power, fatigability, or specific tension, are improved has not been determined. Furthermore, the extent to which these measures of muscle performance are related to testosterone dose or circulating concentration is unknown. To examine the relationship between testosterone dose and muscle performance, 61 healthy, eugonadal young men (aged 18-35 yr) were randomized to 1 of 5 groups, each receiving a long-acting GnRH agonist to suppress endogenous testosterone production plus weekly injections of 25, 50, 125, 300, or 600 mg testosterone enanthate for 20 wk.