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Causes
By Mayo Clinic staffCarcinoid syndrome is caused by a carcinoid tumor that secretes serotonin or other chemicals into your bloodstream. Carcinoid tumors occur most commonly in your gastrointestinal tract, including your stomach, small intestine, appendix, colon and rectum, or in your lungs.
Only a small percentage of carcinoid tumors secrete the chemicals that cause carcinoid syndrome. In most cases, the liver effectively degrades those chemicals before they have a chance to travel through your body and cause symptoms. However, when an advanced tumor spreads (metastasizes) to the liver itself, these tumors may secrete chemicals, which are not degraded before reaching the bloodstream. Most people who experience carcinoid syndrome have an advanced cancer that has spread to the liver.
Some carcinoid tumors don't have to be advanced to cause carcinoid syndrome. For instance, carcinoid lung tumors that secrete chemicals into the blood do so much farther upstream from the liver — not directly into the liver, where the chemicals are processed and eliminated. Carcinoid tumors in the intestine, on the other hand, secrete their chemicals into blood that must first pass through the liver before reaching the rest of the body. The liver usually neutralizes the chemicals before they can affect the rest of the body.
What causes carcinoid tumors is unclear.
- A review of carcinoid cancer. Carcinoid Cancer Foundation. http://www.carcinoid.org/pcf/docs/review.html#SYN. Accessed April 10, 2010.
- How are gastrointestinal carcinoid tumors diagnosed? American Cancer Society. http://www.cancer.org/docroot/CRI/content/CRI_2_4_3X_How_is_gastrointestinal_carcinoid_tumors_diagnosed_14.asp?sitearea=. Accessed April 10, 2010.
- Carcinoid tumor. American Society of Clinical Oncology. http://www.cancer.net/patient/Cancer+Types/Carcinoid+Tumor?sectionTitle=Symptoms. Accessed April 10, 2010.
- Sitaraman SV, et al. Clinical features of the carcinoid syndrome. http://www.uptodate.com/home/index.html. Accessed April 12, 2010.
- Sitaraman SV, et al. Treatment of carcinoid tumors and the carcinoid syndrome. http://www.uptodate.com/home/index.html. Accessed April 12, 2010.
- Connolly HM. Carcinoid heart disease. http://www.uptodate.com/home/index.html. Accessed April 12, 2010.
- Ghevariya V, et al. Carcinoid tumors of the intestinal tract. Southern Medical Journal. 2009;102:1032.
- Bhattacharyya S, et al. Carcinoid heart disease. Circulation. 2007;116:2860.
- Moynihan TJ (expert opinion). Mayo Clinic, Rochester, Minn. April 19, 2010.
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