Sex Steroids and Growth Hormone Secretion

Abstract

The increase in growth velocity seen in puberty is the visible effect of the interaction between sex steroids and growth hormone secretion (GH) and action. This chapter reviews the effects of sex steroids on various aspects of the GH axis. Disease states associated with GH deficiency, hypogonadism, receptor mutations, and enzyme deficiencies have aided the investigation of the mechanisms of action of sex steroids. The rise in testosterone and estrogen during puberty is associated with increase in GH secretion, mediated through the estrogen receptor. Effects on IGF-I production are variable with testosterone increasing GH responsiveness, but estrogen apparently causing dose-related variability in IGF-I production. At the level of the bone, sex steroids likely induce local IGF-I production, and maturation of the epiphyseal region appears to be estrogen dependent. The combined effect of the interactions between sex steroid and the growth GH axis results in an appropriate growth spurt through puberty with a sexual dimorphism in adult height, though the reasons for this difference remain unclear.