Melatonin is primarily produced by the pineal gland but also in the bone marrow, platelets, GI tract, eyes, skin and lymphocytes. Its chemical precursor is serotonin, a neurotransmitter derived from tryptophan. Serotonin must be acetylated and methylated to form melatonin. Synthesis and production of melatonin is affected by light exposure to the eyes; serum concentrations of melatonin are typically low during the daytime hours and increase as night falls. Since it has important effects on circadian rhythms, melatonin has also been reported to have significant effects on reproduction in addition to sleep-wake cycles and antioxidant function.
