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': 'The most common organ involved in MEN I is - \nSelect and explain. \nA. Parathyroid, B. Thyroid, C. Adrenal, D. Testis', 'role': 'user'}, {'content': "Answer: A \nExplanation: Primary hyperparathyroidism (parathyroid gland) occurs in approximately 90% of patients and is the most common feature of MEN 1. Other organs involved are- * Enteropancreatic tumor (30-70%)*Pituitary adenoma (15-50%)*Adrenal coical tumor (20-70%), Pheochromocytoma(<1%), Bronchopulmonary NET(2%), Thymic NET(2%), Gastric NET(10%), Lipomas(>33%), Angiofibromas(85%), Collagenomas(70%), Meningiomas(8%) Reference : page 2336 Harrison's Principles of Internal Medicine 19th edition", 'role': 'assistant'}]