5-HTP, full name 5-Hydroxytryptophan, is a compound synthesized from the naturally derived amino acid tryptophan. It is the precursor of serotonin in the body and is metabolized into serotonin, thereby affecting the brain’s neurotransmitter system. One of the main functions of 5-HTP is to increase serotonin levels. Serotonin is a neurotransmitter that plays an important role in regulating mood, sleep, appetite, and pain perception.