This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
CAMP is a second messenger for a number of hormones and it activates protein kinase for its action. All of the following use cAMP as a second messenger, EXCEPT: 
Select and explain. 
A. Coicotropin, B. Dopamine, C. Glucagon, D. Vasopressin
D: Vasopressin
Answer: D: Vasopressin 
Explanation: Vasopressin uses calcium or phosphatidylinositol (PIP2) as second messengers. Hormones which uses cAMP as the second messenger: ACTH FSH and LH PTH ADH HCG TSH Glucagon Calcitonin Catecholamines Ref: Textbook of Biochemistry by DM Vasudevan, 5th edition, Page 380.