WHAT IS 5-HYDROXYINDOLEACETIC ACID (5-HIAA) (QUANTITATIVE) TEST?
5-HIAA is a primary urinary metabolite of serotonin. Under normal conditions, serotonin is produced in the gastrointestinal tract and acts as a vasoconstrictor. Approximately 5% of serotonin is converted to 5-HIAA and excreted in the urine. Increased urinary 5-HIAA is reflective of overproduction of serotonin, which occurs with carcinoid tumours.