Melatonin (N-acetyl-5-methoxytryptamine) is a product of tryptophan metabolism. It is synthesized in the pineal gland and is secreted to control the circadian rhythm. Melatonin is also synthesized in the gastrointestinal tract, retina, skin and other tissues where it acts in a autocrine or paracrine manner. The role of melatonin in these tissues is independent of its role in the circadian rhythm, where it plays a role in energy metabolism, physiological growth, differentiation and responsiveness in stress stimuli. The pleiotropic effects of melatonin have given rise to various therapeutic possibilities for this molecule. For example; anti-stress, sexual dysfunction, obesity, gallbladder stones. To date, the only therapeutic uses for melatonin remain to treat sleep disorders, depression, migraine and headaches.