5-HIAA -->
5-hydroxyindole acetic acid
medical dictionary

<tumour marker>

<biochemistry> This is a metabolite of serotonin that is excreted in the urine.

Serotonin is a neurotransmitter that is synthesised from the amino acid tryptophan by enterochromaffin cells in the gut and bronchi. It is metabolised to 5-hydroxyindole acetic acid in the liver and then excreted in the urine.

Elevations in 5-hydroxyindole acetic acid can indicate carcinoid tumour. The normal range in a 24 hour urine collection is 3 to 15 mg per 24 hours.

Acronym: 5-HIAA

Abbreviation: 5-HIAA

(13 Nov 1997)