Posted in Web Carcinoid Syndrome: Symptoms, Causes, Treatment, Diet, Prognosis January 12, 2021 Carcinoid syndrome is a condition in which a carcinoid tumor releases serotonin or other chemicals into the bloodstream. Carcinoid tumors, which develop most commonly in the gastrointestinal (GI)… https://www.healthline.com/health/carcinoid-syndrome