<P> In primates, the developmental influence of androgens is less clear, and the consequences are less understood . Within the brain, testosterone is aromatized to (estradiol), which is the principal active hormone for developmental influences . The human testis secretes high levels of testosterone from about week 8 of fetal life until 5--6 months after birth (a similar perinatal surge in testosterone is observed in many species), a process that appears to underlie the male phenotype . Estrogen from the maternal circulation is relatively ineffective, partly because of the high circulating levels of steroid - binding proteins in pregnancy . </P> <P> Sex steroids are not the only important influences upon hypothalamic development; in particular, pre-pubertal stress in early life (of rats) determines the capacity of the adult hypothalamus to respond to an acute stressor . Unlike gonadal steroid receptors, glucocorticoid receptors are very widespread throughout the brain; in the paraventricular nucleus, they mediate negative feedback control of CRF synthesis and secretion, but elsewhere their role is not well understood . </P> <P> The hypothalamus has a central neuroendocrine function, most notably by its control of the anterior pituitary, which in turn regulates various endocrine glands and organs . Releasing hormones (also called releasing factors) are produced in hypothalamic nuclei then transported along axons to either the median eminence or the posterior pituitary, where they are stored and released as needed . </P> <Dl> <Dt> Anterior pituitary </Dt> </Dl>

What part of the brain controls the endocrine system