title: Serotonin metabolism in patients with carcinoid tumors: incidence of 5-hydroxytryptophan-secreting tumors.
abstract: The urinary excretion of 5-hydroxyindoleacetic acid, 5-hydroxytryptophan, serotonin, tryptamine, and tyramine and the serum serotonin concentration were determined in 38 consecutive patients with metastatic carcinoid tumors. Four of the 23 patients with the carcinoid syndrome (15%) had markedly elevated excretion of 5-hydroxytryptophan. None of the patients had markedly elevated excretion of tryptamine or tyramine; a substantial number of patients had moderately low urinary excretion of these amines. All of the patients with the carcinoid syndrome had elevated urinary 5-hydroxyindoleacetic acid excretion; 2 of these patients had normal serum serotonin concentrations, suggesting that quantitative 5-hydroxyindoleacetic acid excretion is the most reliable test for the carcinoid syndrome. Although tryptamine secretion by carcinoid tumors is rare, 5-hydroxytryptophan secretion may be more common than is recognized.
mesh_terms: D006916:5-Hydroxytryptophan / Q000378:metabolism* / Q000652:urine; D000328:Adult; D000368:Aged; D002276:Carcinoid Tumor / Q000097:blood / Q000378:metabolism* / Q000652:urine; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000378:metabolism / Q000652:urine; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000652:urine; D008113:Liver Neoplasms / Q000378:metabolism / Q000652:urine; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D012701:Serotonin / Q000097:blood / Q000652:urine; D014363:Tryptamines / Q000652:urine; D014439:Tyramine / Q000652:urine
chemical_list: D014363:Tryptamines; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D006916:5-Hydroxytryptophan; D014439:Tyramine