Tryptophan, an essential amino acid obtained from the diet, is the source for the production of serotonin, a neurotransmitter that sends messages from nerve cell to nerve cell in your body. Serotonin, manufactured in the brain, lungs and small intestine, functions to convey nerve impulses and produces blood vessel constriction. Testing for serotonin has limitations based on health conditions, medications and food restrictions.
Significance
Since it is primarily stored in blood platelets, testing the blood for serotonin levels is useful as a diagnostic screening tool for individuals with a family history of multiple endocrine neoplasia. This genetic disease increases the potential for carcinoid tumors of the glands of the endocrine system. Carcinoid syndrome, a condition resulting from the tumor-induced rise in serotonin, occurs as a consequence of the spread of cancer to the liver. Symptoms include cramps, diarrhea, flushing of the face, fast heart rate and wheezing.
Carcinoid Tumors
Carcinoid tumors occur most often in the gastrointestinal tract and are slow growing. The most likely areas of tumor origin, by descending order of appearance, is the small intestine, rectum, colon, appendix and stomach. Carcinoids are usually malignant and the spread of cancer correlates with the size and location of the tumor. Carcinoids secrete a number of hormones including serotonin, somastatin and gastrin.
Restrictions
Serotonin blood testing does not have food restrictions. Certain medications affect test results, such as morphine, lithium, methyldopa and reserpine. Follow your physician's instructions concerning medications. Certain pre-existing conditions increase serotonin levels including cystic fibrosis, bowel obstructions, heart attack and a gastrointestinal disorder called dumping syndrome. With these conditions, serotonin testing is not normally ordered.
Complimentary Testing
Serotonin breaks down in the liver to 5-hydroxyindoleacetic acid or 5-HIAA which stimulates muscle and is eliminated in the urine. Levels of 5-HIAA, measured from a 24-hour urine collection, help with initial serotonin blood testing, detecting sporadic serotonin release, monitoring therapy for carcinoid tumors and determining the return of a tumor. The 5-HIAA test requires food restrictions for 3 days before and during the test including caffeine, avocados, bananas, tomatoes, plums, walnuts, pineapple, eggplant, kiwi, plantains as well as nicotine. Follow your physician's instruction for medication restrictions.
References
- St. Francis Health: Preparing for Lab Work
- Lab Tests Online: Serotonin
- Mount Nittany Medical Center: Serotonin Test
- Drugs.com: Serum Sertonin Level
- Lab Tests Online: 5-HIAA
- "Current Medical Diagnosis & Treatment"; Stephen J. McPhee and Maxine A. Papadakis; 2008
