Serotonin

Diagnose carcinoid syndrome.

In general, EDTA whole blood (as compared to serum) preserved with ascorbic acid will give values most representative of blood concentrations. Most (95%) of blood serotonin is found in platelets, thus a properly preserved whole blood sample is preferable. See Serotonin, Whole Blood [120089].

Serotonin is produced by cells of the APUD system, including the enterochromaffin (Kulchitsky) cells distributed through the mucosa of the gastrointestinal tract. Most serotonin in blood is usually concentrated in platelets, which release it during blood coagulation. Serotonin may be measured to confirm the diagnosis of carcinoid syndrome. The carcinoid syndrome is usually caused by primary carcinoids of the ileum, but the syndrome is occasionally caused by primary carcinoids of the stomach. Other organs give rise to carcinoids including pancreas, duodenum, bronchus, and ovary. Most patients with the carcinoid syndrome have hepatic metastases.

Monoamine oxidase inhibitor drugs should be discontinued for at least one week prior to sampling since they tend to increase the level of serotonin.