5-hydroxyindole acetic acid

5-hydroxyindole acetic acid

5-HIAA A biogenic amine found especially in the brain and other organs, which accounts for 1% of degraded tryptophan; 5-HIAA may be markedly–25-50-fold normal ↑ in carcinoid tumors, especially of the midgut–less commonly of lung and ovary–features of carcinoid syndrome–eg, bronchoconstriction, diarrhea, flushing, right-sided heart lesions, facial telangiectasia; 5-HIAA is also ↑ in Hartnup's disease, nontropical sprue, in some mental conditions Drugs Acetaminophen, caffeine, l-dopa, glyceryl, guaiacolate, heparin, nicotine, phenothiazine, reserpine, salicylates; 5-HIAA is ↓ in major GI tract resection, renal insufficiency, PKU, phenothiazine therapy