Dopamine, norepinephrine and serotonin production by an intestinal carcinoid tumor.

Substantial amounts of both dopamine and norepinephrine in addition to serotonin were found in a mesenteric metastasis of an ileal carcinoid tumor. Correspondingly, the norepinephrine-synthesizing enzymes were present in the tumor tissue and tyrosine hydroxylase was found in amounts substantially higher than the levels normally present in adrenal medullary cells. These findings confirm that the carcinoid tumors belong to the APUDomas and indicate that catecholamines might play an important role in the pathogenesis of the carcinoid syndrome.