This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Surgery
Most common cause of hypersecreting pitutary tumor is? 
Select and explain. 
A. Pitutary adenoma, B. Pitutary carcinoma, C. Autoimmune disease of pituitary, D. Transection of stalk
A: Pitutary adenoma
Answer: A: Pitutary adenoma 
Explanation: ANSWER: (A) Pitutary adenomaREF: Harrison's 18th ed chapter 339, 341Most common cause of hypersecreting pitutary tumors is pitutary adenoma