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
[{'content': 'True statement about primary hyperparathyroidism- \nSelect and explain. \nA. Adenoma commonest cause, B. serum calcium, C. Surgery if biochemical finding is abnormal in asymptomatic patient, D. MIBG isotope is useful in localization of tumor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Solitary adenoma common cause around 80% of primary hyperparathyroidism Ref - ( Harrison 17 pg 2380)', 'role': 'assistant'}]