5-hydroxy Indole-3-acetic acid (5-HIAA) is a metabolite of the monoamine neurotransmitter serotonin .1 It is formed from serotonin via a 5-hydroxy indole-3-acetaldehyde intermediate by aldehyde dehydrogenase. 5-HIAA has been used as a biomarker for the detection of neuroendocrine tumors. Brain levels of 5-HIAA are decreased in patients with severe Alzheimer’s disease.2
1.Corcuff, J.-B., Chardon, L., El Hajji Ridah, I., et al.Urinary sampling for 5HIAA and metanephrines determination: Revisiting the recommendationsEndocr. Connect.6(6)R87-R98(2017) 2.Vermeiren , Y., Van Dam, D., Aerts, T., et al.Monoaminergic neurotransmitter alterations in postmortem brain regions of depressed and aggressive patients with Alzheimer's diseaseNeurobiol. Aging35(12)2691-2700(2014)