HIAA; 5-hydroxy indole acetic acid; Serotonin metabolite
5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin. In the chemical analysis of urine samples, 5-HIAA is used to determine serotonin levels in the body.5-HIAA is a urine test that measures the amount of 5-hydroxy indole acetic acid (5-HIAA). 5-HIAA is a breakdown product of a hormone called serotonin.
5-HIAA is a urine test that measures the amount of 5-hydroxyindoleacetic acid (5-HIAA). 5-HIAA is a breakdown product of a hormone called serotonin. This test tells how much 5-HIAA the body is producing. It is also a way to measure how much serotonin is in the body.
This test tells how much 5-HIAA the body is producing. It is also a way to measure how much serotonin is in the body. 5-HIAA is tested by 24-hour urine samples combined with an acidic additive to maintain pH below 3. Certain foods and drugs are known to interfere with the measurement. 5-HIAA levels can vary depending on other complications, including tumors, renal malfunction, and small bowel resection.
Since 5-HIAA is a metabolite of serotonin, testing is most frequently performed for the diagnosis of carcinoid tumors of the enterochromaffin (Kultschitzsky) cells of the small intestine, which release large amounts of serotonin. Values greater than 25 mg per 24 hours (higher if the patient has malabsorption) are strong evidence of carcinoid. The normal range is 2 to 6 mg per 24 hours.[rx]
Low levels of 5-HIAA in the cerebrospinal fluid have been associated with aggressive behavior and suicide by violent means, correlating with diminished serotonin levels.[rx]
Elevated serotonin (hyperserotonemia) is one of the most common biological findings in autism[rx] and 5-HIAA may be elevated in patients with autistic spectrum disorders.
How the Test is Performed
A 24-hour urine sample is needed. You’ll need to collect your urine over 24 hours in a container provided by the laboratory. Your health care provider will tell you how to do this. Follow instructions exactly.
How to Prepare for the Test
Your provider will instruct you, if necessary, to stop taking medicines that may interfere with the test.
Medicines that can increase 5-HIAA measurements include acetaminophen (Tylenol), acetanilide, phenacetin, glyceryl guaiacolate (found in many cough syrups), methocarbamol, and reserpine.
Medicines that can decrease 5-HIAA measurements include heparin, isoniazid, levodopa, monoamine oxidase inhibitors, methenamine, methyldopa, phenothiazines, and tricyclic antidepressants.
You will be told not to eat certain foods for 3 days before the test. Foods that can interfere with 5-HIAA measurements include plums, pineapples, bananas, eggplant, tomatoes, avocados, and walnuts.
How the Test will Feel
The test involves only normal urination, and there is no discomfort.
Why the Test is Performed
This test measures the level of 5-HIAA in the urine. It is often done to detect certain tumors in the digestive tract ( carcinoid tumors ) and to track a person’s condition.
The urine test may also be used to diagnose a disorder called systemic mastocytosis and some tumors of the hormone.
Normal Results
The normal range is 2 to 9 mg/24h (10.4 to 46.8 µmol/24h).
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What Abnormal Results Mean
Abnormal results may be due to:
- Tumors of the endocrine system or carcinoid tumors
- Systemic mastocytosis
Risks
There are no risks with this test.
