Melatonin

Endogenous melatonin is a naturally produced hormone primarily synthesized and secreted in the pineal gland. Melatonin regulates the body's sleep-wake cycles by interacting with the suprachiasmatic nucleus of the hypothalamus and the retina. The best-known purpose of melatonin is its role in promoting sleep and inhibiting wake-promoting signals through interactions with its MT1 and MT2 receptors. Although melatonin is not officially approved for any indication by the US Food and Drug Administration (FDA) in the United States, exogenously supplied melatonin, which is available as a synthetic dietary supplement, mimics the regulatory functions of endogenous melatonin.