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: Surgery
Commonest cause of Cushings syndrome is - 
Select and explain. 
A. Adrenal adenoma, B. Carcinoma, C. Hyperplasia, D. Atrophy
C: Hyperplasia
Answer: C: Hyperplasia 
Explanation: "In most cases, the cause is bilateral adrenal hyperplasia due to hypersecretion of pituitary ACTH or ectopic production of ACTH by a nonpituitary source."- Harrison