This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S., Subject name: Medicine
[{'content': 'A 47-year-old woman presents with increasing headaches and visual changes. On examination, her pupils are normal and reactive to light, the extraocular movements are normal, and there are visual field defects of the outer half in both eyes (bitemporal hemianopsia). Which of the following is the most likely diagnosis? \nSelect and explain. \nA. pituitary adenoma, B. falx meningioma, C. craniopharyngioma, D. aneurysm of the internal carotid artery', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Adenomas of the pituitary gland constitute approximately 7% of intracranial tumors, with the chromophobic type being the most common. With macroadenomas, some degree of pituitary insufficiency is common, and half the patients have headaches. With microadenomas, the other pituitary functions may be completely normal.', 'role': 'assistant'}]