PHYSIOLOGY OF PUBERTY

Puberty is not a single event but one stage in development. The endocr ine events of puberty in many ways recapitulate previous changes in th e fetus. It is currently not known what triggers puberty at an appropr iate time. It appears that puberty is restrained by higher central ner vous system controls, but the restraint can be eliminated by injury or tumor growth resulting in premature puberty. The first endocrine even t of puberty is an increase in the amplitude of gonadotropin pulses at night due to increased pulsatile release of hypothalamic gonadotropin -releasing hormone (GnRH) into the hypothalamic-pituitary portal syste m. This is reflected by an increase in luteinizing hormone secretion a fter a bolus of exogenous GnRH. Gonadal steroids are produced due to i ncreased gonadotropin stimulation, and secondary sexual development fo llows a well-described pattern of changes. The pubertal growth spurt r esults from an increase in growth hormone secretion induced by sex ste roids as well as from local production of growth factors. Positive fee dback leads to the onset of menses and ovulation in girls by mid-puber ty or later. This physical and reproductive maturity occurs in an orde rly pattern, of which the physiology is described and in large part un derstood.