5-Hydroxy Indole Acetic Acid (5-HIAA)
4.7 - 36.2 µmol/24hr
Time Limit for Add on Tests:
Target Turnaround time:
Further Information from LabTestsOnline
Measurement of urinary 5-HIAA is useful in the diagnosis and monitoring of patients with the carcinoid syndrome. The syndrome is caused by carcinoid tumors, which are small slowly growing tumors of enterochromaffin cells.
Enterochromaffin cells are part of the neuroendocrine system and most of them produce serotonin. Excessive serotonin secretion is responsible for many of the symptoms associated with the carcinoid syndrome. Serotonin is primarily metabolized to 5 HIAA in the liver and kidney. 5 HIAA is water soluble and excreted almost entirely in the urine. Measurement of urinary 5 HIAA is recommended for patients with suspected carcinoid syndrome. More than 90% of patients with the carcinoid syndrome have 5 HIAA levels that exceed 75 umol per 24 hours. If two 24-hour urine collections during spells fail to reveal an increased 5 HIAA level, the diagnosis of a functioning carcinoid is unlikely.