5-Hydroxy-Indole Acetic Acid (5-HIAA), 24 Hrs Urine


5-HIAA is the major product of the oxidative de-amination of serotonin, a derivative of the amino acid tryptophan. Serotonin is a potent muscle stimulant and vasoconstrictor that is formed in the enterochromaffin c cells of the gastrointestinal tract. Thus, 5-HIAA levels reflect serotonin synthesis. See Also 5-Hydroxytryptophan , and Serotonin


5-HIAA levels are increased in metastatic carcinoid tumours. High 5-HIAA levels are associated with midgut carcinoids, while slight elevations are associated with non-tropical sprue. Decreased levels are found in phenylketonuria, renal insufficiency, depression and small intestine resection.

Sample Type, Quantity & Conditions

30 ml of 24 Hrs urine

Special Precautions

State 24 Hrs urine volume. Adjust pH to (3-6) with Hydrochloric Acid.

Normal Range

< 15.0 mg/24 Hrs < 78.45 nmol/ 24Hrs

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