To help diagnose a carcinoid tumor that produces serotonin
Serotonin
Serotonin
Also Known As
5-Hydroxytryptamine
5-HT
Formal Name
Serotonin
This article was last reviewed
on
This article waslast modified
on November 5, 2017.
At a Glance
Why Get Tested?
When To Get Tested?
When you have symptoms suggestive of a carcinoid tumor, such as flushing, diarrhea, and/or wheezing
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
Accordion Title
Common Questions
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How is it used?
A serotonin test may be used to help diagnose carcinoid tumors. It may be ordered along with, or following, a 24-hour urine 5-HIAA test.
Carcinoid tumors are slow-growing masses that can form in the gastrointestinal tract (especially in the appendix) and in the lungs, although they may affect other organs as well. They are one of several types of tumors that arise from cells in the neuroendocrine system, cells that are found in organs throughout the body and that have both nerve and endocrine aspects.
The serotonin test is not generally used as a monitoring tool to evaluate the effectiveness of treatment or to detect recurrence of a carcinoid tumor. Chromogranin A and 5-HIAA may be used for this purpose.
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When is it ordered?
This test is primarily ordered when a person has symptoms suggestive of a carcinoid tumor.
Some signs and symptoms include:
- Flushing of the face and neck (appearance of deep red color, usually with sudden onset)
- Diarrhea, nausea, vomiting
- Rapid heart rate
- Wheezing, coughing, difficulty breathing
This test may be ordered initially or as a follow-up test when 5-HIAA test results are normal or near normal.
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What does the test result mean?
A significantly increased level of serotonin in a person with carcinoid syndrome symptoms is suggestive but not diagnostic of a carcinoid tumor. In order to diagnose the condition, the tumor itself must be located, biopsied, and examined by a pathologist. The healthcare practitioner will frequently follow an abnormal test result with an order for an imaging scan to help locate any tumor(s) that may be present.
Someone may still have a carcinoid tumor even if the concentrations of serotonin and 5-HIAA are normal. Some carcinoid tumors do not produce serotonin or only produce it intermittently.
A person with no symptoms and normal levels of serotonin and 5-HIAA is unlikely to have a serotonin-secreting carcinoid tumor.
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Is there anything else I should know?
There are a variety of drugs that can affect the serotonin test, including morphine, monoamine oxidase (MAO) inhibitors (such as reserpine), methyldopa, and lithium. People should talk to their healthcare provider before decreasing or discontinuing any medications.
Serotonin concentrations may be slightly increased in those with intestinal obstruction, acute myocardial infarction (heart attack), cystic fibrosis, and dumping syndrome. The serotonin test is not usually ordered with these conditions.
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Should I have both the serotonin and 5-HIAA tests performed?
Serotonin and 5-HIAA offer complementary information. In some cases, 5-HIAA is preferred because it is more stable and, since it is collected for 24 hours, there is more chance of detecting increased 5-HIAA than in identifying excess serotonin that is only released intermittently. Talk to your healthcare practitioner about which tests are appropriate for your condition.
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Are some people at a higher risk for developing a carcinoid tumor?Anyone at any age can develop a carcinoid tumor but, according to the American Cancer Society, the average age at diagnosis is usually about 55 to 65. People with a family history of multiple endocrine neoplasia (MEN1), a genetic condition that increases a person's risk of developing tumors in the endocrine system glands, may be at higher risk for developing a carcinoid tumor.
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How does a healthcare practitioner locate the carcinoid tumor?
This is usually accomplished through the use of imaging scans such as x-rays, computed tomography (CT), or magnetic resonance imaging (MRI). In some cases, surgery is required to find the tumor. For more on these imaging tests, visit RadiologyInfo.org.
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How does the healthcare practitioner tell whether a tumor is benign or cancerous?
In order to determine whether the tumor is benign or cancerous, the healthcare practitioner will need to perform a biopsy or remove the tumor surgically. The tumor is sent to the laboratory and a pathologist will examine the tumor cells under the microscope. (For more, see the article on Anatomic Pathology.)
