Source: Gonadal steroids and body composition, strength, and sexual function in men. Finkelstein JS, Lee H, Burnett-Bowie S-A, et al. N Engl J Med 2013;369:1011–22.
Low testosterone levels are widely recognized to be associated with decreases in lean mass and strength, an increase in body fat and impaired sexual function, and testosterone treatment can reverse these changes. However, the effects of a decline in estrogen, which is produced from testosterone, also need to be considered as it plays an important role in bone metabolism and regulation of body fat and sexual function.