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

Oxidation of iodine
Organification
Coupling