Androgens and their role in skeletal homeostasis.

Androgens are needed during the entire lifespan of the male skeleton -at least in the rat. Indeed, in aged nongrowing male rats, androgens are necessary for the maintenance of skeletal integrity. In these animals, androgen deficiency results in a menopause-like acceleration of bone turnover and bone loss which are presented by androgen replacement. In the growing skeleton, androgens probably have a twofold effect. Not only neonatal androgens but also pubertal androgen secretions are needed for normal skeletal growth and modeling in order to reach full size (cortical) bone mass. Moreover, androgens are not only necessary for the (cortical) bone mass but also for the maintenance of cancellous bone compartment during growth, at least in androgen-deficient rats. However, both animal experiments and recent human data suggest that at least part of the complex skeletal effects of androgens may depend on the aromatization of androgens into estrogens.