Carcinoid syndrome occurs when a rare cancerous tumor called a carcinoid tumor secretes certain chemicals into your bloodstream, causing a variety of signs and symptoms. A carcinoid tumor, which is a type of neuroendocrine tumor, occurs most often in the gastrointestinal tract or the lungs.

Carcinoid syndrome typically occurs in people who have carcinoid tumors that are advanced. Treatment for carcinoid syndrome usually involves treating the cancer. However, because most carcinoid tumors don’t cause carcinoid syndrome until they’re advanced, a cure may not be possible. Medications may be recommended to relieve your carcinoid syndrome symptoms and make you more comfortable.

Having carcinoid syndrome can cause the following complications:

Carcinoid heart disease. Some people with carcinoid syndrome develop carcinoid heart disease. Carcinoid syndrome causes problems with the heart valves, making it difficult for them to function properly. As a result, the heart valves may leak. Signs and symptoms of carcinoid heart disease include fatigue and shortness of breath. Carcinoid heart disease can eventually lead to heart failure. Surgical repair of damaged heart valves may be an option.