5-HTP from Primaforce:

5-HTP (5-Hydroxytryptophan) is the immediate precursor to serotonin (5-HT, 5-hydroxytryptamine). Serotonin plays an important role in the regulation of mood, appetite, body temperature, and the secretion of various hormones. 5-Hydroxytryptophan (5-HTP or 5-Hydroxy-l-tryptophan) is an amino acid that converts in the brain into a chemical called serotonin. It is believed that, due to the stress-filled era of modern living, people have lower levels of serotonin in the brain. This can cause people to become overweight, crave sugar and other carbohydrates, experience bouts of emotional imbalance, get frequent headaches, and have vague muscle aches and pain. By raising the levels of serotonin in the brain, these problems can be corrected.