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: Pathology
Most common cause of Cushing's syndrome is? 
Select and explain. 
A. Pitutary adenoma, B. Adrenal adenoma, C. Adrenal carcinoma, D. McCune Albright syndrome
A: Pitutary adenoma
Answer: A: Pitutary adenoma 
Explanation: Ans. is 'a' i.e., Pitutary adenoma ACTH-secreting pituitary adenomas account for approximately 70% of cases of endogenous hypercoisolism (Cushing's syndrome).