Melatonin (N-acetyl-5-methoxytryptamineis) is a
hormone produced by the pineal gland somewhere in the brain. So it is naturaly
produced by this gland when its dark.
On most sleep products that contain melatonin, it says on the package do not take if you have an endocride disorder. So thats a good enough reason for me. I researched it once on the web, forgot the details, but since it did not make me more sleepy, I just dropped it anyway.