ENDOCRINE FUNCTIONS OF THE BRAIN

The brain, like the gut and vascular endothelium, contains many bioact ive materials in addition to the classical neurotransmitters. The brai n is a composite structure and contains several discrete endocrine ass ociations (pineal gland, pituitary, hypothalamus) whose outputs are te mpered by direct neuronal influences (neuromodulators). The principal hormone of the pineal is melatonin, which has widespread actions, bein g anti-gonadal, and seems to be a key factor in regulating light/dark (day/night), diurnal/nycthemeral activities. The hypothalamus produces a range of hormones that have systemic (being released into the gener al circulation) and relatively local actions upon the pituitary gland, via the hypothalamo-hypophysial portal system. The brain contains man y hormones that belong to 'hormonal families' that variously affect go nadal, thyroid, adrenocortical and central behavioural features. The b rain also contains enzymes that can modify hormones to change their ac tivities (androgens can be converted to oestrogens, for example). One can conclude that the brain is not only the seat of consciousness and thought, but also a resource which governs the activities al probably all cells and organs, by virtue of he hormones that ii produces for lo cal and systemic use.