<prompt> The causal mechanism in carcinoid syndrome is due toErythropoietin and immunoglobulinSerotonin and bradykininInsulin and insulin like substancesACTH and ACTH like substances  <response>: Carcinoid syndrome develops in 10 of carcinoid tumours due to release of 5-HT serotonin, kinins, prostaglandins, histamine and indoles causing flushing, diarrhoea, cyanosis, asthmatic attacks, hepatomegaly, cardiac lesion on right side.. Reference : page 878 SRBs manual of surgery 5th edition 