25 Jul
5-Hydroxyindoleacetic acid (5HIAA) is the major metabolite of serotonin and is excreted in the urine. Intestinal carcinoid tumors and neuroendocrine tumors
can produce high amounts of 5-HIAA and serotonin, especially in patients with carcinoid syndrome. Assay of 5-HIAA in a 24-hour urine specimen can aid in diagnosis of carcinoid disease
with a high specificity.