This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Lalloo, 50 years old, a chronic smoker, presents with history of hemoptysis. He was having truncal obesity and hypeension. He had an elevated ACTH level which was not suppressive with high dose dexamethasone. What would be the most probable diagnosis 
Select and explain. 
A. Bilateral adrenal hyperplasia, B. Adrenal adenoma, C. Pituitary tumour, D. Ectopic| ACTH producing lung cancer
D: Ectopic| ACTH producing lung cancer
Answer: D: Ectopic| ACTH producing lung cancer 
Explanation: ectopic increase in ACTH is not suppressed by high dose of dexamethasone ( Harrison 17 pg 2256 )