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: Pharmacology
[{'content': "The thyroid inhibitor which produces the fastest response is \nSelect and explain. \nA. Lugol's iodine, B. Propylthiouracil, C. Radioactive iodine, D. Lithium carbonate", 'role': 'user'}, {'content': 'Answer: A \nExplanation: IODINE AND IODIDES Though iodine is a constituent of thyroid hormones, it is the fastest acting thyroid inhibitor. Ref:- kd tripathi; pg num:-254', 'role': 'assistant'}]