Melatonin, receptors, mechanism, and uses

Melatonin, a hormone produced primarily by the pineal gland, is also secreted from the gut and eye during darkness. There are three classes of melatonin receptors, MT₁, MT₂, and MT₃, in various regions of the human brain, gut, ovaries, and blood vessels, but most consistently found in the suprachiasmatic nucleus (SCN) of the hypothalamus and the pars tuberalis of the anterior pituitary. Melatonin has endocrine, autocrine, and paracrine actions, which are mostly receptor mediated. Primary clinical uses include the regulation of circadian rhythms and sleep disorders, although it has other endocrine, immunomodulatory, and oncostatic effects. This review summarizes the current state of melatonin research with an emphasis on its receptors, pharmacological effects, and clinical therapeutic uses.