Sex hormones, body composition and aging

Abstract

In order to evaluate the role of sex hormones and aging on body composition in males, plasma testosterone, free testosterone, estradiol and sex hormone binding globulin as well as insulin-like growth factor I (IGF-I) and insulin levels were determined in a group of 372 ambulant males, aged 20- 85 years. In addition, these parameters were correlated with aging and body composition. Muscle mass decreased and fat mass increased significantly with age. Both age and free testosterone were independent determinants off at mass. Abdominal fat was by far the most important determinant of free testosterone levels, gluteal fat contributing little to the free testosterone levels. The decrease of fat free mass was essentially correlated with age, the contribution of free testosterone levels being marginal. The ratio of subcutaneous to visceral fat decreased with age, independent of body mass index, free testosterone or estradiol levels. This suggests that, at a similar degree of obesity, the health hazards are more pronounced in elderly men. IGF-I levels correlated negatively with fat mass, but this correlation was lost after adjustment for age. The negative correlation off at mass with (free) testosterone levels persisted after correction for IGF-I levels, suggesting that the decrease of free testosterone levels is an independent co-determinant of the age-associated increase in fat mass. Hence, it may be concluded that the age-associated decrease in androgen levels plays an important role in the changes in body composition, independent of the effect of age itself or the age-associated decrease in IGF-I levels.