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.

OBJECTIVE

To examine the relationship between different measures of testosterone and estradiol (E(2)), 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 E(2) 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.

RESULTS

Appendicular skeletal mass (ASM) was positively associated with total testosterone (TT; P<0.001), free testosterone (FT; P<0.001), and total E(2) (P<0.001) but not with free E(2) (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 E(2), but not free E(2) was associated with lower grip strength (P<0.05) after adjustment for age, FT, SHBG and relative ASM.

CONCLUSIONS

Testosterone level was related to both muscle mass, strength and physical performance. Total E(2) level, though related to muscle mass positively, affected muscle strength adversely in older men.