| 5-hydroxytryptamine | <biochemistry, hormone> A neurotransmitter and hormone (176 kD), found in vertebrates, invertebrates and plants. It is synthesised from the amino acid tryptophan by enterochromaffin cells in the gut and bronchi. It is metabolised to 5-HIAA in the liver and then excreted in the urine. Serotonin is measured on a venipuncture specimen in cases of suspected carcinoid syndrome (where it will be elevated). The normal range is 101 to 283 ng/ml. Acronym: 5-HT (13 Nov 1997) |
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