Estrogen treatment and estrogen suppression: metabolic effects in adolescence

The metabolic consequences of reaching full reproductive maturity in humans involve not only growth hormone (GH) and insulin-like growth factor-I, but also the collaborative interaction of the gonadal sex steroids. Estrogen is critical for completing linear growth. It also inhibits bone resorption, decreases plasma lipid levels and serves as an antiatherosclerotic agent. Our studies show that, in low doses, estrogen increases GH production, increases calcium absorption and decreases bone turnover; however, unlike testosterone, estrogen has no effects as a protein-anabolic agent, at least at the whole body level. Studies of selective estrogen suppression, achieved using a potent aromatase inhibitor, show that estrogen is the main regulator of the gonadotropin axis. In boys, selective aromatase blockade may have a role in delaying epiphyseal fusion. Large placebo-controlled trials will be required to study this effect further.