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.
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.
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.
This article was last reviewed on December 17, 2015. | This article was last modified on December 17, 2015.
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