Testosterone but not estradiol level is positively related to muscle strength and physical performance independent of muscle mass: a cross-sectional study in 1489 older men

Abstract

ObjectiveTo 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 methodsA cross-sectional survey on 1489 community-dwelling men older than 64 years of age. Serum levels of testosterone and E2were 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.ResultsAppendicular 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 E2was associated with lower grip strength (P<0.05) after adjustment for age, FT, SHBG and relative ASM.ConclusionsTestosterone level was related to both muscle mass, strength and physical performance. Total E2level, though related to muscle mass positively, affected muscle strength adversely in older men.