Endocrine function similar to that of puberty occurs during the fetal period (Figs 13.9). The fetal hypothalamus and pituitary gland are connected via the pituitary portal system by twenty weeks of gestation, ten weeks after the formation of gonadotrophs in the pituitary gland and of gonadotrophin-releasing hormone (GnRH) in the hypothalamus. By midgestation, serum gonadotrophin levels are exceptionally high and, in midgestational males, testosterone is secreted by the fetal testes in large amounts. The fetal overy responds to similar stimulation from the fetal pituitary gland. As fetal development proceeds, gonadotrophin secretion and sex steroid production decrease but do not disappear.
