To examine the relationship between different measures of testosterone and estradiol (E2), muscle mass, muscle strength, and physical performance; and to test whether the association of sex hormone level with muscle strength and physical performance was independent of muscle mass.
Design and methods
A cross-sectional survey on 1489 community-dwelling men older than 64 years of age. Serum levels of testosterone and E2 were measured by mass spectrometry, and sex hormone-binding globulin (SHBG) levels were measured by immunoradioassay. Muscle mass was examined by dual-energy X-ray absorptiometry and physical performance was assessed by hand-grip strength, gait speed, step length and chair-stand test.
Appendicular skeletal mass (ASM) was positively associated with total testosterone (TT; P<0.001), free testosterone (FT; P<0.001), and total E2 (P<0.001) but not with free E2 (P=0.102). After adjustment for age, serum SHBG and relative ASM, both TT and FT were significantly associated with grip strength, narrow-walk speed and the composite neuromuscular score. Higher total E2, but not free E2 was associated with lower grip strength (P<0.05) after adjustment for age, FT, SHBG and relative ASM.
Testosterone level was related to both muscle mass, strength and physical performance. Total E2 level, though related to muscle mass positively, affected muscle strength adversely in older men.