This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CNS Tumors, Subject name: Surgery
A 30 years old male complains of loss of erection; he has low testosterone and high prolactin level in blood; what is the likely diagnosis:- 
Select and explain. 
A. Pituitary adenoma, B. Testicular failure, C. Craniopharyngioma, D. Cushing's syndrome
A: Pituitary adenoma
Answer: A: Pituitary adenoma 
Explanation: Most common cause of hypersecreting pituitary is Pituitary adenoma. PITUITARY ADENOMA Pituitary adenomas arise primarily from anterior pituitary glandQ Classified as either functional (secreting) or nonfunctional (non-secreting) tumors MC functional tumor is prolactinomaQ, which causes amenorrhea & galactorrhea in womenQ. MRI is IOC for pituitary tumorsQ