All of these hormones use cAMP as second messenger except:

Ans. (D) Vasopressin(Ref: Katzung 11/e p301, Gationg 22/e p41-43)Vasopressin acts via V1 and V2 receptors. V1 receptors use IP3 -DAG-Ca2+ pathway whereas V2 use cAMP as second messenger. All other drugs mentioned in the question act by cAMP pathway only. Thus, all of these use cAMP as second messenger, but if we need to choose one option we can answer vasopressin as it is acting through IP3 -DAG-Ca2+ pathway also.