Use

This test measures urinary 5-hydroxyindoleacetic acid (5-HIAA), a principal metabolite of serotonin, which is useful in diagnosing and monitoring treatment of carcinoid syndrome, particularly related to serotonin-secreting neuroendocrine tumors. The presence of elevated 5-HIAA levels in the urine can indicate well-differentiated functional gastroenterohepatic neuroendocrine tumors, and correlate with carcinoid syndrome severity. Compared to those with normal levels, elevated urinary 5-HIAA levels are associated with a poorer prognosis and can reveal excessive conversion of tryptophan to serotonin.