Purpose Loss of muscle mass and strength contributes to increased risk of falls and fractures, affecting our independence and quality of life. We conducted a systematic review of clinical trials to determine the effects of testosterone (T) replacement on FFM, muscle strength, and physical function in young hypogonadal men and in middle-aged and older men with low T levels.
Methods In a review of randomized, placebo-controlled trials in middle-aged and older men using testosterone in replacement doses for ≥ 90 days, seven trials were found which met the inclusion criteria. In hypogonadal men, we found 15 clinical trials that used testosterone in 1,299 hypogonadal men; most of these studies were open-label trials. Odds ratios were pooled using a random effects model, assuming heterogeneous results across studies, after weighting for sample size. The Clopper-Pearson method was used to compute 95% confidence intervals.
Results Testosterone replacement in middle-aged and older men was associated with a significantly greater increase in FFM (2.5 kg, 95% CI 1.5, 3.4), grip strength (3.3 kg, 95% CI 0.7, 5.8 kg) and a greater reduction in whole-body fat mass (-2.1 kg, 95% CI -3.1, -1.1) than placebo. Testosterone replacement of hypogonadal men was associated with an average 2.8 kg gain in FFM and 1.1 kg gain in body weight.
Conclusions Testosterone consistently increases FFM and grip strength to a greater extent than placebo in middle-aged and older men. The studies were performed in asymptomatic men; further studies are needed to determine testosterone's effects in older men with disability or symptomatic physical impairment. These first-generation studies do not have sufficient power to detect changes in health-related quality of life or disability.
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