It is only a few years since Thorson1 and others recognized the association of several unusual signs and symptoms with carcinoid tumors of the small bowel with hepatic metastases. It is apparent now that (1) carcinoid (argentaffinoma) is an endocrine tumor which produces the pharmacologically active agent, serotonin (5-hydroxytryptamine), and (2) the various manifestations of the "carcinoid syndrome" are attributable to secretion of serotonin by the tumors and a disturbance in the metabolism of tryptophan.2 Since many cases of the disorder have now been recognized,3,4 both the general practitioner and the specialist should be aware of this condition and become acquainted with the simple chemical test 5 on urine by which it may be diagnosed.
A series of baffling illnesses extending over a period of years is typical, coinciding with slow growth of the tumor. Current clinical concepts are derived chiefly from study of advanced
SJOERDSMA A. Clinical and Laboratory Features of Malignant Carcinoid. AMA Arch Intern Med. 1958;102(6):936-938. doi:10.1001/archinte.1958.00260230082011