title: Improved diagnosis of carcinoid tumors by measurement of platelet serotonin.
abstract: Carcinoid patients are diagnosed biochemically on the basis of increased urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA); urinary and platelet serotonin concentrations are considered to provide complementary information. Using established HPLC methods with fluorometric detection, we evaluated the clinical usefulness of measurements of urinary 5-HIAA and urinary, plasma, and platelet serotonin in 30 consecutive patients with histologically proven carcinoid tumors of fore-, mid-, and hindgut origin before treatment. Ten patients showed no signs of serotonin overproduction; 14 had increased concentrations of urinary 5-HIAA and platelet serotonin; and platelet serotonin, but not urinary 5-HIAA, was increased in 6. None had increased urinary 5-HIAA excretion without an increase in platelet serotonin content. In cases with high rates of tumor serotonin secretion, platelet serotonin reached a maximum and did not correlate with serotonin secretion rate, whereas urinary 5-HIAA was correlated. Increased platelet serotonin was correlated with increased plasma serotonin and with occurrence of carcinoid syndrome. Increased urinary serotonin, allegedly caused by increases in circulating 5-hydroxytryptophan, almost invariably coincided with increased platelet serotonin, but not necessarily with above-normal urinary 5-HIAA excretion. From these results and long-term monitoring of three patients during treatment, we conclude that platelet serotonin is more sensitive than urinary 5-HIAA for detecting carcinoids that secrete only small amounts of serotonin.
authors.affiliation: Central Laboratory for Clinical Chemistry, University of Groningen, The Netherlands.
authors.forename: I P
authors.initials: IP
authors.lastname: Kema
authors.forename: E G
authors.initials: EG
authors.lastname: de Vries
authors.forename: A M
authors.initials: AM
authors.lastname: Schellings
authors.forename: P E
authors.initials: PE
authors.lastname: Postmus
authors.forename: F A
authors.initials: FA
authors.lastname: Muskiet
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000378:metabolism*; D002276:Carcinoid Tumor / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D005260:Female; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000652:urine; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012701:Serotonin / Q000097:blood* / Q000652:urine
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid