Serotonin Metabolite

5-Hydroxyindoleacetic acid (5-HIAA) is a major metabolite of serotonin, generated via a two step process, involving monoamine oxidase A (MAO-A) and aldehyde dehydrogenase. Measurement of 5-HIAA in combination with serotonin may offer insight into mechanisms underlying various clinical symptoms. The ratio of serotonin to 5-HIAA may be used to evaluate serotonin turnover and monoamine oxidase activity. Abnormal levels of 5-HIAA have been associated with depression, suicidal behaviors, aggression, chronic psychotropic medication use, and Parkinson’s Disease.