Within our central nervous system Serotonin plays a critical part in in the regulation of Depression, Anxiety, Sleep, Aggression, Temperature, Appetite, Sexual Behaviour and the Sensation of Pain. Cells in other parts of the body also use and make Serotonin, but all Serotonin used by our Brain Cells has to be made within the Neurons, as Serotonin cannot cross the blood-brain barrier. Serotonin is produced by an Amino Acid called Tryptohan.
5-Hydroxytryptophan, (5-HTP), is also an Amino Acid naturally produced by the body from the essential Amino Acid Tryptohan through a process called Enzyme Tryptophan Hydroxylase.  The action of Tryptophan Hydroylase can be inhibited by many different influences, some of these include, Stress, Vitamin B6 deficiency, and Insulin Resistance, thus making the Tryptophan unavailable for Serotonin production.  As mentioned earlier, if not enough Serotonin is produced then the regualtion of  Depression, Anxiety, Sleep, Aggression, Temperature, Appetite, Sexual Behaviour and the Sensation of Pain, may be effected.
