Previous research has determined that men are more likely than women to lose muscle mass and strength as they age, and this has been linked to declining endogenous serum testosterone (T) levels. Similarly, exogenous T supplementation in older men is positively correlated with increases in lean body mass, improved muscle strength, and decreased fat mass.
A prospective study of 1183 ambulatory men in the Osteoporotic Fractures in men study across 6 US centers measured serum total T, estradiol, and sex hormone binding globulin (SHBG) levels; physical strength via bilateral grip strength, various walking parameters, and timed chair stands; and body composition via DEXA scans over a 4.5 year period. Nearly 40% of men who lost more than 2.0-kg in the follow-up period exhibited a decreased decline in lean appendicular mass at higher baseline T levels compared to men with lower or normal T levels. Estradiol was not found to be correlated to body composition or changes in physical function or strength.
The authors concluded that higher levels of serum T were associated with decreased loss of lean muscle mass and lower extremity strength in men over 65 years of age. Higher T levels were more strongly associated with preservation of appendicular lean mass, which may translate to health outcomes related to frailty. The authors admit that higher T levels may not necessarily correlate with less decline in overall physical function. A limitation of the study posits that not every factor which may impact sex hormones could be adequately controlled for, and that trials with longitudinal measurements of sex steroid hormones are needed to establish an association between serum levels and body composition and physical function.
Reference: LeBlanc ES, Wang PY, Lee CG, et al. Higher testosterone levels are associated with less loss of lean body mass in older men. J Clin Endocrinol Metab 2011;96:3855-63.