The role of estrogens in men and androgens in women.

The past years several have witnessed a significant transformation in our understanding of sex steroid action in the male and female skeleton. Data from animal and human studies indicate that sex steroids have important skeletal effects in both genders. It seems from the in vivo human data that estrogen is likely more potent than testosterone in inhibiting bone resorption. Estrogen and testosterone appear to be important for maintaining bone formation. In addition, androgens clearly enhance bone size, likely through effects on periosteal bone formation. How much of this gender cross-talk at the physiological level is caused by "promiscuous" actions of sex steroids at the molecular level, with estrogen acting by way of the androgen receptor (and androgens via the estrogen receptor) is an interesting and important question, the answer to which may well provide additional surprises.