All are TRUE about carcinoid syndrome, EXCEPT:

Serotonin does not appear to be involved in the flushing because flushing is not relieved by serotonin receptor antagonists. Flushing associated with it affects predominantly upper pa of the body especially the neck and face. In patients with carcinoid hea disease, 97% have tricuspid insufficiency, 59% tricuspid stenosis, 50% pulmonary insufficiency, 25% pulmonary stenosis, and 11% (0-25%) left-side lesions. Midgut carcinoids account for 60-67% of cases of carcinoid syndrome, foregut tumors for 2-33%, hindgut for 1-8%, and an unknown primary location for 2-15%. Ref: Harrisons principles of internal medicine, 18th edition, Page: 3063.