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