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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;PP2(P2(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 (PConclusionsTestosterone 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.

ObjectiveAssociation studies in men have shown that androgens are inversely related to fat measures, while the relation between sex steroids and lean mass remains unclear. We, therefore, investigated the associations between serum sex steroid levels and body composition in elderly men with a main focus on lean mass measures.Design and methodsA cross-sectional survey of a population-based cohort of 3014 elderly men, aged 69–80 years (Osteoporotic Fractures in Men study, Sweden). Serum levels of testosterone and estradiol (E2) were measured by mass spectrometry, sex hormone-binding globulin (SHBG) levels were measured by IRMA, and measures of body composition were obtained by dual-energy X-ray absorptiometry.ResultsTotal as well as free serum testosterone associated independently inversely (P2associated independently directly (P2and free E2but not serum testosterone or free testosterone levels associated positively with lean mass (P2had 0.5 kg less lean mass in the legs than subjects within the highest quartile, while the subjects in the different quartiles of free testosterone did not differ in lean mass.ConclusionsSerum E2, but not serum testosterone, is directly associated with lean mass in this large study of elderly Swedish men. In addition, serum SHBG is associated with central fat distribution and we confirmed that serum testosterone is inversely associated with fat mass.

Sex steroids are important for the growth and maintenance of both the female and the male skeleton. However, the relative contribution of androgens versus estrogens in the regulation of the male skeleton is unclear. Experiments using mice with inactivated sex steroid receptors demonstrated that both activation of the estrogen receptor (ER)α and activation of the androgen receptor result in a stimulatory effect on both the cortical and trabecular bone mass in males. ERβ is of no importance for the skeleton in male mice while it modulates the ERα-action on bone in female mice. Previous in vitro studies suggest that the membrane G protein-coupled receptor GPR30 also might be a functional ER. Our in vivo analyses of GPR30-inactivated mice revealed no function of GPR30 for estrogen-mediated effects on bone mass but it is required for normal regulation of the growth plate and estrogen-mediated insulin-secretion. Recent clinical evidence suggests that a threshold exists for estrogen effects on bone in men: rates of bone loss and fracture risk seem to be the highest in men with estradiol levels below this threshold. Taken together, even though these findings do not exclude an important role for testosterone in male skeletal homeostasis, it is now well-established that estrogens are important regulators of bone health in men.