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: Pharmacology
[{'content': 'Mechanism of action of propylthiouracil in hyperthyroidism is: \nSelect and explain. \nA. Inhibition of organification of iodine, B. Inhibition of oxidation of iodine, C. Inhibition of coupling of two DIT residues, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Propylthiouracil, carbimazole and methimazole act by inhibiting the enzyme, thyroid peroxidase. It catalyses:\n\nOxidation of iodine\nOrganification\nCoupling', 'role': 'assistant'}]