Puberty is often defined as the period of first becoming capable of sexual reproduction. It is marked by the adolescent growth spurt, maturation of the genital organs, development of secondary sexual characteristics, first ejaculation in boys and onset of menstruation (the menarche) in girls. There are also psychosocial characteristics resulting from the effects of increased gonadal sex steroid production and the resultant maturational changes in the CNS. Puberty is a temporal process involving transition and development. One conspicuous feature of sexual development in the human is the prolonged interval between birth and initiation of the pubertal process. Initiation of spermatogenesis and ovarian cyclicity does not normally occur until early in the second decade of life, and then only after a stage of ‘entering’ puberty lasting several years has taken place.

A change in gonadal activity as a major component of puberty was apparent more than 2000 years ago as knowledge of the effects of castration during prepubertal development began to accumulate. Similarly, knowledge that these changes in gonadal activity are of a humoral nature is not modern either. The ancients used castration as a form of punishment, and well beyond the Middle Ages castration was used in European cultures to retain the quality of the unbroken male voice and ally it with the lung capacity of the adult. These days, of course, the pleasant counter tenor is the result of voice training not castration. In the early 1900s, transplantation experiments gave new insights in the understanding of the mechanism of puberty. It was observed that transplantation of the ovaries from an immature animal into an adult led to the premature onset of pubertal activity in the transplanted gonad.