Carcinoid syndrome is caused by carcinoid tumors that most commonly arise in the mucosa of the gastrointestinal tract. Carcinoid syndrome is the set of symptoms that may occur in patients who have carcinoid tumors. Not all people with carcinoid tumors have carcinoid syndrome. The syndrome occurs when carcinoid tumors overproduce substances such as serotonin that normally circulate throughout your body. This overproduction of serotonin and other hormones is what causes the symptoms of carcinoid syndrome.
Other (non-carcinoid) tumors can also cause symptoms similar to those of carcinoid syndrome. These can include tumors in the duodenum and the lung. Another such tumor is called a VIPoma. "VIP" stands for Vasoactive Intestinal Peptide. VIPomas are extremely rare and can cause severe, watery diarrhea that requires immediate care.
If you have carcinoid syndrome, or diarrhea caused by a VIPoma, it is important to visit your healthcare provider regularly. Your healthcare provider will also explain your treatment options.