Mechanism of action of propylthiouracil in hyperthyroidism is:: (A) Inhibition of organification of iodine, (B) Inhibition of oxidation of iodine, (C) Inhibition of coupling of two DIT residues, (D) All of the above
Answer is D. Propylthiouracil, carbimazole and methimazole act by inhibiting the enzyme, thyroid peroxidase. It catalyses:

Oxidation of iodine
Organification
Coupling