Melatonin

Melatonin (N-acetyl-5-methoxytryptamine) is a derivative of tryptophan, an amino acid, and a hormone produced by the pineal gland located right at the center of the brain, and responsible for biological, circadian rhythm of our body. Production of melatonin is light dependent: pineal gland synthesizes more melatonin at night, and less during daytime or under light illumination, while serotonine (5-hydroxytryptamine, or 5-HT), another brain hormone derived from tryptophan, is produced more during the daytime and less at night. Prolonged night time or reduced exposure to light (for example, due to seasonal change or weather) leads to "SAD" (seasonally affected disorder) or "winder blues", a psychiatric disorder accompanied by depression affecting 25 million individuals in the US alone, may be associated with melatonin over-production.