Melatonin

Melatonin is a hormone secreted by the pineal gland in response to darkness, signalling biological night and helping align the circadian system. It facilitates sleep onset, modulates core body temperature, and exerts antioxidant effects. Endogenous melatonin declines with age, and bright evening light suppresses its release. Low-dose exogenous melatonin is used to address jet lag, shift work, and delayed sleep-phase patterns.