This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and breast, Subject name: Anatomy
Commonest cause of Cushings syndrome is 
Select and explain. 
A. Adrenal adenoma, B. Carcinoma, C. Atrophy, D. Hyperplasia
D: Hyperplasia
Answer: D: 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.