Mechanism of action of propylthiouracil in hyperthyroidism is:
Propylthiouracil, carbimazole and methimazole act by inhibiting the enzyme, thyroid peroxidase. It catalyses:

Oxidation of iodine
Organification
Coupling
Inhibition of organification of iodine
Inhibition of oxidation of iodine
Inhibition of coupling of two DIT residues
All of the above