Carcinoid syndrome is caused by the release of certain hormones and other substances from a carcinoid tumor. These tumors are slow-growing cancers that typically develop in the gastrointestinal tract, such as in the appendix, small intestine, or rectum, but can also occur in the lungs.
The primary hormone that causes carcinoid syndrome is serotonin, which is normally found in the brain and plays a role in regulating mood, sleep, and appetite. When a carcinoid tumor releases large amounts of serotonin into the bloodstream, it can cause a wide range of symptoms. Other hormones and substances that can be released by carcinoid tumors and contribute to the syndrome include histamine, prostaglandins, and bradykinin.
The exact cause of carcinoid tumors is not known, but they are thought to develop from cells in the walls of the digestive tract. Some factors that may increase the risk of developing carcinoid tumors include:
- smoking
- exposure to certain chemicals,
- a rare family syndrome called multiple endocrine neoplasia type 1 (MEN1)
- parents with squamous cell skin cancer, non-Hodgkin’s lymphoma, or cancer of the brain, breast, liver, womb, bladder or kidney
- conditions called neurofibromatosis or tuberous sclerosis
Carcinoid syndrome typically occurs in people with advanced or metastatic carcinoid tumors, and the symptoms can be severe and debilitating. Treatment options include surgery to remove the tumor, chemotherapy, and medications to control symptoms.