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: 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 suppressible 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: Answer is D (Ectopic ACTH producing lung cancer) Truncal obesity, hypeension and elevated ACTH levels suggest a diagnosis of Cushing's syndrome. Elevated ACTH level not suppressible by high dose Dexamethasone indicate the diagnosis of Cushing's syndrome due to Ectopic ACTH production.