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
Most common cause of primary hyperparathyroidism is: 
Select and explain. 
A. Solitary adenoma, B. Chief cell hyperplasia, C. Multiple adenoma, D. Werner's syndrome
A: Solitary adenoma
Answer: A: Solitary adenoma 
Explanation: Answer is A (Solitary adenoma) The most common cause of primary hyperparathyroidism is a Solitary Parathyroid Adenoma Q Adenomas are most commonly located in the inferior parathyroid gland. Q