The endocrinology of puberty

Abstract

The hypothalamic-pituitary-gonadal axis is unique among the hypothalamic-pituitary hormonal systems in that it undergoes dramatic changes in biologic activity during fetal, childhood, and adult development. Unlike the other pituitary hormonal systems, the axis is quiescent for much of childhood, becoming active at the developmental stage that defines puberty. Puberty begins when the gonadotropin-releasing hormone (GnRH) neurons of the hypothalamus secrete GnRH in a pulsatile manner. Pulsatile GnRH causes pituitary gonadotrophs to synthesize and release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH in turn induce steroidogenesis and gametogenesis in the gonads. Steroid production then causes the physical and physiological changes associated with puberty. A single pathway or factor that triggers this hormonal cascade at puberty has not been found, although several pathways have been identified that affect GnRH neuron function at puberty. This chapter will first discuss the physiology of the reproductive axis in intrauterine life and childhood, detailing the hormonal signals and receptor function of normal puberty. Next, genes implicated in pubertal timing will be discussed in context of the disease processes that result from the genetic derangement. Finally, secular trends in pubertal timing will be discussed.