The Role of Androgens and Estrogens in the Male Skeleton

Past several years have witnessed a dramatic shift in the understanding of sex steroid regulation of the male skeleton. Androgens are clearly important for bone metabolism in males; what has been unexpected is the major role played by estrogen (E). With respect to men, convincing new evidence from multiple lines of investigation shows clearly that E is an important, if not the dominant sex steroid in regulating male bone metabolism. Although age-related bone loss in men had generally been assumed to be independent of sex steroids, it appears that the observed decreases in circulating bioavailable E and testosterone (T) levels may well be contributing to the development of involutional osteoporosis in men. These findings also suggest the possibility that other disorders associated with aging in men, such as cardiovascular disease, dementia, and prostate cancer, may also be related to these changes in sex steroid and in particular E levels.