Androgens and body composition in the aging male.

The relevant age-related changes in male body composition are mainly related to the progressive decrease in the level of circulating anabolic hormones, among which testosterone (T) is rather important. Its decline, between the ages of 35 and 75, is associated to a loss of muscle mass and fibers number, a doubling of fat mass and a decrease in bone mineral density by 0.3% per yr after age 35; thus the relationship between age-related changes in body composition and T bioactivity reflects an important endocrine aspect of the aging male. The assessment of human body composition and in particular the evaluation of fat tissue and its distribution, is currently standardized by the use of dual-energy x-ray absorpiometry (DXA). In the present paper we review the mechanisms through which testosterone may inhibit adipogenesis, restore the myogenic programme enhancing the protein turnover at muscle level and maintain bone mineral density in elderly men.