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Interpretive Handbook

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Test 9248:
5-Hydroxyindoleacetic Acid (5-HIAA), Urine

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

5-Hydroxyindoleacetic acid (5-HIAA) is the major metabolite of serotonin and is excreted in the urine. Intestinal carcinoid tumors along with neuroendocrine tumors can produce excess amounts of 5-HIAA and serotonin especially in individuals with carcinoid syndrome. Carcinoid syndrome is characterized by carcinoid tumors, flushing, heart disease, and hepatomegaly. Normally 1% to 3% of dietary tryptophan is metabolized to serotonin. However, as much as 50% of tryptophan is converted to serotonin in patients with the intestinal carcinoid syndrome.

 

Measurement of 5-HIAA in a 24-hour urine specimen can diagnose carcinoid disease with a high specificity.

Useful For Suggests clinical disorders or settings where the test may be helpful

Biochemical diagnosis and monitoring of intestinal carcinoid syndrome

Interpretation Provides information to assist in interpretation of the test results

Elevated excretion of 5-hydroxyindoleacetic acid is a probable indicator of the presence of a serotonin-producing tumor, if pharmacological and dietary artifacts have been ruled out.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Intake of food with a high content of serotonin (avocados, bananas, plums, walnuts, pineapple, eggplant, plantains, tomatoes and tomato products, hickory nuts, kiwifruit, dates, grapefruit, butternuts, melons, nuts, pecans, cantaloupe, or honeydew melon) within 48 hours of the urine collection could result in falsely elevated 5-hydroxyindoleacetic acid (5-HIAA) excretion.

 

Numerous drugs affect the excretion of 5-HIAA by different mechanisms, including increased serotonin synthesis, metabolism, and release and inhibition of uptake. See "Update on Serotonin" in the August 2006 Communique' in Publications, as well as Clinical References #3 and #4, for a detailed list of potentially interfering drugs.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Adults: < or =8 mg/24 hours

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. de Herder W: Biochemistry of neuroendocrine tumours. Best Pract Res Clin Endocrinol Metab 2007 Mar;21(1):33-41

2. Manini P, Andreoli R, Cavazzini S, et al: Liquid chromatography-electrospray tandem mass spectrometry of acidic monoamine metabolites. J Chromatogr B Biomed Sci Appl 2000 July 21;744(2):423-431

3. Mashige F, Matsushima Y, Kanazawa H, et al: Acidic catecholamine metabolites and 5-hydroxyindoleacetic acid in urine: the influence of diet. Ann Clin Biochem 1996;33:43-49

4. Mills K: Serotonin syndrome - A clinical update. Crit Care Clin 1997;13:763-783

5. Serotonin syndrome. In POISINDEX System. Edited by RK Klasco, CR Gelman, LT Hill. Greenwood Village, Colorado, Micromedex, 2002