Puberty is a period of dynamic changes in growth and body composition, which are mediated by growth hormone and sex steroid hormones. Although they exert important independent effects, the interaction between growth hormone and the sex steroid hormones is vital to normal growth and pubertal development. Studies using nonaromatizable androgens and selective receptor blockade have shown that the effects of sex steroid hormones on growth and the growth hormone-IGF-I axis is through an estrogen-receptor-mediated process. Similarly, estrogen is essential for normal skeletal maturation and mineralization in both male and female adolescents.