5-hydroxyindoleacetic Acid

Ayyan Web

The 5-hydroxyindoleacetic acid (5-HIAA) test is used to help diagnose and monitor carcinoid tumors. It can be ordered alone or together with a serotonin and / or chromogranin A blood level. This test is ordered primarily when you have signs and symptoms that suggest a carcinoid tumor.

Also Known as: HIAA, Serotonin Metabolite, 5-HIAA, 5-hydroxyindoleacetic Acid, 24 hour Urine 5-hydroxyindoleacetic acid, 24 hour 5-HIAA,

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Why get tested ?

To help diagnose and monitor treatment for a serotonin-producing carcinoid tumor.

When to get tested ?

When you have symptoms that suggest a carcinoid tumor, such as redness, abdominal pain, diarrhea and / or wheezing; at intervals after treatment

Mechanism:

  • Serotonin (5-Hydroxytryptamine) produced by Carcinoid
  • Serotonin converted to 5-HIAA for excretion

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

Increased Urine 5-HIAA 24 hour Levels

  • Malignant Carcinoid (>25 mg/day)
  • Acute Intestinal Obstruction
  • Celiac Sprue
  • Excessive Banana or walnut ingestion

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