Serotonin metabolism in patients with carcinoid tumors: incidence of 5-hydroxytryptophan-secreting tumors.
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.[1]References
- Serotonin metabolism in patients with carcinoid tumors: incidence of 5-hydroxytryptophan-secreting tumors. Feldman, J.M. Gastroenterology (1978) [Pubmed]
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