[Skip to Navigation]
[Skip to Navigation Landing]
August 1959

Serotonin and the 5-Hydroxyindole Pathway of Tryptophan Metabolism

Author Affiliations


From the Medical Clinic, Peter Bent Brigham Hospital, and the Department of Medicine, Harvard Medical School; Junior Associate in Medicine, Peter Bent Brigham Hospital, and Assistant in Medicine, Harvard Medical School (Dr. Donaldson); Physician, Peter Bent Brigham Hospital, and Associate Clinical Professor of Medicine, Harvard Medical School (Dr. Gray).

AMA Arch Intern Med. 1959;104(2):330-338. doi:10.1001/archinte.1959.00270080156022

The presence of a vasopressor factor in clotted defibrinated blood has been known for 90 years. This factor, serotonin, was isolated from blood platelets and identified as 5-hydroxytryptamine in 1948, by Rapport. In 1937, enteramine, a smooth muscle constrictor which was later found to be identical with serotonin, was isolated from intestinal mucosa by Erspamer. He suggested that enteramine was a hormonal substance secreted by the argentaffin cells of the intestine. Intense interest in this entire subject was stimulated by recognition of the disease entity, malignant carcinoidosis. The syndrome is caused by malignant carcinoid tumors (argentaffinomas), which contain large quantities of serotonin. Patients with carcinoidosis have increased amounts of serotonin in the blood and large quantities of 5-hydroxyindoleacetic acid, the major metabolite of serotonin, in the urine. The clinical features of the carcinoid syndrome include episodic flushing of the skin, patchy cyanosis, telangiectasia, pellagra-like skin lesions, bronchoconstriction, edema, atypical valvular