5-HIAA-High Titer

5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin. In chemical analysis of urine samples, 5-HIAA is used to determine serotonin levels in the body.

Since 5-HIAA is a metabolite of serotonin, testing is most frequently performed for the diagnosis of carcinoid tumors of the enterochromaffin cells of the small intestine, which release large amounts of serotonin. Elevated serotonin is one of the most common biological findings in autism and 5-HIAA may be elevated in patients with autistic spectrum disorders.