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': 'Most common cause of primary hyperparathyroidism- \nSelect and explain. \nA. Iatrogenic, B. Medullary carcinoma thyroid, C. Parathyroid adenoma, D. Parathyroid hyperplasia', 'role': 'user'}, {'content': "Answer: C \nExplanation: Most common cause of primary hyperparathyroidism is autonomous secretion of parathyroid hormone (PTH) by a parathyroid adenoma. Single adenoma (90%), multiple adenomas(4%), nodular hyperplasia(5%), carcinoma(1%). Reference : page 769 Davidson's Principles and practice of Medicine 22nd edition", 'role': 'assistant'}]