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24 hour Urine 5-hydroxyindoleacetic acidAka: 24 hour 5-HIAA

Indications
1. Carcinoid Syndrome Evaluation
Mechanism
1. Serotonin (5-Hydroxytryptamine) produced by Carcinoid
2. Serotonin converted to 5-HIAA for excretion
Interpretation
1. Normal: Urine 5-HIAA < 9 mg/day
2. Equivocal: Urine 5-HIAA 9 to 25 mg/day
  1. Possibly consistent with Carcinoid Syndrome
  2. See Other causes of 5-HIAA elevation
3. High: Urine 5-HIAA >25 mg/day
  1. Diagnostic for Carcinoid Syndrome
Increased Urine 5-HIAA 24 hour Levels
1. Malignant Carcinoid (>25 mg/day)
2. Acute Intestinal Obstruction
3. Celiac Sprue
4. Excessive Banana or walnut ingestion

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This page was written by Scott Moses, MD. This page was last revised before 5/10/08, prior to consistent tracking of revision date. This page was last published on 5/10/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 6.0.