Carcinoid syndrome is a group of symptoms that occur in some people with carcinoid tumors, which are a type of slow-growing cancer that usually starts in the digestive system. These tumors can release hormones, particularly serotonin, into the bloodstream, leading to various symptoms. Common symptoms of carcinoid syndrome include flushing of the skin, diarrhea, and wheezing. These symptoms arise when the hormones enter the bloodstream and affect different parts of the body. Treatment options may include medications to control symptoms and surgery to remove the tumors if possible.