Higher testosterone levels are associated with less loss of lean body mass in older men.

Context: Little information exists about longitudinal changes in body composition and physical function in relation to sex hormone levels in older men.
Objective: The aim of the study was to determine associations of testosterone, estradiol, and SHBG with changes in body composition and physical function.
Design and Setting: We conducted a prospective cohort study within the Osteoporotic Fractures in Men (MrOS) study at six U.S. clinical centers.
Participants: A total of 5994 ambulatory men aged 65 yr or older enrolled in the MrOS. We examined 1183 men with complete measures of sex steroid hormones, body composition, and some measure of physical function.
Intervention: There were no interventions.
Main Outcome Measure(s): Sex steroids were measured by mass spectrometry in serum collected at baseline. Measurements of body composition using dual-energy x-ray absorptiometry and physical performance (grip strength, leg power, timed chair stands, narrow walk, and 6-m walk) were performed at baseline and repeated 4.5 yr later.
Results: Overall, men lost 1.3 kg (±4.4 sd) weight between study visits. Lean mass, especially appendicular, declined less at higher baseline testosterone levels (P < 0.05). These associations were most evident in the 40% of men who lost more than 2.0 kg during follow-up. In weight losers, higher testosterone was associated with less decline in timed chair stands. Estradiol was not related to body composition or physical function changes. Higher SHBG was associated with less loss of appendicular lean mass and grip strength.
Conclusions: Higher endogenous testosterone is associated with reduced loss of lean mass and lower extremity function in older men losing weight. Endogenous testosterone may contribute to healthy aging.