Testosterone Dose-Dependently Increases Skeletal Muscle Mass (SMM) in Healthy Men

Abstract

1661 Skeletal muscle mass is the largest component of the fat-free mass in humans; its loss as a result of disuse atrophy and/or disease results in sarcopenia and reduced function perhaps leading to disability. PURPOSE: to determine testosterone's effects on SMM in a sample of 60 young (mean ± SD: 26 ± 15, range18–36yrs) 61 older (66 ± 4, 60–75yrs) healthy men. METHODS: Subjects were randomly assigned to receive one of five doses (25, 50, 125, 300, or 600 mg/week) of testosterone enanthate (TE) for 20 weeks plus a GnRH agonist monthly to clamp endogenous testosterone. Body composition was determined by DEXA. Total appendicular lean soft tissue mass (ALST) was calculated as the sum of ALST mass for right and left legs plus right and left arms. SMM was estimated from these data using the Kim equation (AJCN, 2002). RESULTS: Linear regression analysis revealed a significant (r = 0.76, P<0.001) testosterone dose-SMM relationship. Two-way ANOVA revealed a significant dose effect (P < 0.001), with increases in SMM in men receiving 125, 300, or 600 mg (* P < 0.05) of testosterone per week compared to those receiving 25 or 50 mg/week. There was no age effect. CONCLUSIONS: Testosterone significantly and dose-dependently increases SMM in healthy men with no differences in response to testosterone dose between older and younger men.Figure