Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter produced by serotonergic neurons in the CNS and enterochromaffin cells in the gastrointestinal tract. Pharmacologic action of serotonin is mediated by a large and diverse range of 5-HT receptors. Serotonin plays an important part in the biochemistry of depression, migraine, bipolar disorder, and anxiety. It is also believed to be influential on sexuality and appetite. Creatinine is a product of the metabolic breakdown of creatine phosphate in muscle. Creatinine is filtered by healthy kidneys. Serotonin creatinine sulfate complex was the first isolated salt form of serotonin.