Specimen Information

Type

Gold, SST

Volume

1.0 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Frozen

CRITICAL FROZEN Separate samples must be submitted when multiple tests are ordered

Fasting Required?

False

Clinical Significance

Serotonin (5-hydroxytryptamine, 5-HT) is derived from tryptophan and is transported in blood by platelets. This smooth muscle stimulant is oxidatively deaminated to 5-hydroxyindoleacetic acid (5-HIAA). Increased concentrations of circulating serotonin have been implicated in several pathologic conditions that may involve peripheral serotonergic mechanisms: carcinoid syndrome, migraine, schizophrenia, essential hypertension, Huntington disease, and Duchenne muscular dystrophy. Slight increases may be seen in dumping syndromes, acute intestinal obstruction, cystic fibrosis, acute myocardial infarction (MI), and nontropical sprue. In carcinoid tumors, serotonin is variably metabolized to 5-HIAA, depending upon the tissue of origin (foregut, midgut, hindgut). The majority of patients usually have very high concentrations of urinary 5-HIAA. Metastasizing abdominal carcinoid tumors are often associated with concentrations greater than 400 ng/ mL. Medications that may affect serotonin concentrations include: lithium, MAO inhibitors, methyldopa, morphine, and reserpine. In general, serotonin-containing foods do not interfere significantly.