Many friends read online knowledge that lung cancer patients will also have carcinoid syndrome, so what is carcinoid syndrome of lung cancer? Carcinoid syndrome is related to the release of different vasoactive substances from lung cancer cells, including 5-hydroxytryptamine, bradykinin, vasopressin and catecholamines, among others. It is typically characterized by abnormalities in skin, cardiovascular, gastrointestinal and respiratory functions. The main manifestations are flushing or edema of the face and upper trunk, increased gastrointestinal motility, diarrhea, tachycardia, wheezing, pruritus and sensory abnormalities. These symptoms will generally decrease or resolve with effective treatment.