That would be melatonin. This is a hormone normally produced by the pituitary gland, which is often poisoned in amalgam illness, and the reason why mercury toxic people don't sleep very well.

The sublingual variety works best (doesn't have to be absorbed by the intestinal tract) and can be bought over the internet. If you have adrenal problems be careful - it drives down cortisol, so you shouldn't take more than 0.5 - 1.5mg. It DOES help with sleeping.