Serotonin, Blood

Serotonin is an indole amine synthesized by the cells of the intestinal mucosa. It is stored in and transported by platelets but also found in many body tissues, including the CNS. Serotonin acts as a vasoconstrictor and neurotransmitter; stimulant of smooth muscle contraction, prolactin release, and GH release; and functions in hemocoagulation. Other names: 5-hydroxytryptamine.

Normal range: 50 " “200 ng/mL.

Use

Confirming the diagnosis of carcinoid tumors.

Adjunct test for 5-HIAA and chromogranin-A test to follow-up patients with carcinoid tumors.

Interpretation

Increased In

Metastasizing abdominal carcinoid tumors

Dumpling syndrome

Acute intestinal obstruction

Cystic fibrosis

AMI and nontropical sprue

Oat cell carcinoma of the lung

Pancreatic islet tumor

Thyroid medullary carcinoma

Decreased In

Down syndrome

Severe depression

Parkinson disease

Phenylketonuria (treated and untreated)

Renal insufficiency

Teratomas

Limitations

Blood serotonin is very unstable.

Medications that may affect serotonin concentrations include lithium, MAO inhibitors, methyldopa, morphine, and reserpine.

In general, foods that contain serotonin do not interfere significantly.

Slight increases may be seen in acute intestinal obstruction, acute MI, cystic fibrosis, dumping syndromes, and nontropical sprue.