Serotonin

Serotonin test is used to measure the levels of serotonin in the blood. This is useful in diagnosing carcinoid tumor. A carcinoid tumor is a type of cancer, which can be found in small intestine, colon, appendix, bronchial tubes in the lungs, liver, pancreas, kidneys, prostate or ovaries and thymus. These tumors grow slowly and are capable of spreading to other parts. Some of the carcinoid tumors convert tryptophan into a chemical called serotonin.

What is Serotonin?

Serotonin is a chemical substance which transmits messages between nerve cells and plays an important role in learning or memory, regulating your mood, affects your sleep cycle, appetite and digestion. Serotonin is derived from tryptophan which is an amino acid. It is produced mainly from the brain and by some special cells in bronchial tubes and gastrointestinal tract. Serotonin present in the blood helps in constriction of the blood vessels. Most of the serotonin in the blood is found in platelets. Carcinoid tumors intermittently or continuously produce serotonin in large quantities. Hence, an increase in the level of serotonin may indicate the presence of carcinoid tumor.

Why this test is performed?

This test may be recommended to you if you experience symptoms like rapid heart rate, wheezing, flushing of the face, neck, upper body, visible blood vessels on the face and neck, tiredness, diarrhea, nausea, vomiting, abdominal pain, and all these symptoms together are called carcinoid syndrome, which is associated with carcinoid tumor. Usually, this test is given to you along with other tests like 5-HIAA in urine. This test is also recommended to you to evaluate the treatment if you are already diagnosed with a carcinoid tumor.

Precautions: Some of the foods may interfere with the test results showing false-positive. These foods include bananas, tomatoes, pineapples, kiwis, avocados, eggplants, walnuts, plums, hickory nuts, pecans, etc. Some medicines may also interfere with the test results such as MAO inhibitors (Selegiline, Tranylcypromine, Isocarboxazid, Phenelzine), lithium, morphine, reserpine, methyldopa, etc. Besides smoking, alcohol, caffeine, imbalances due to hormones also influence the serotonin levels. Hence inform your doctor or technician about all your current medications and medical conditions prior to the test.

The normal test results may vary depending on gender, age, health history, etc.

Higher levels of serotonin in the blood may indicate the presence of carcinoid tumor. But in some conditions even if the serotonin levels are normal there may be chances of a carcinoid tumor because the carcinoid tumors do not produce serotonin or it may produce it intermittently.

Low or normal levels of serotonin are unlikely to have a serotonin-secreting tumor.

If you get abnormal test results to consult your doctor immediately. Your doctor may recommend other tests depending on your results because serotonin test alone can not decide the presence of carcinoid tumor.