Which of the following drugs inhibit 5'-deiodinase?: (A) Propylthiouracil, (B) Methimazole, (C) Lugol's iodine, (D) Radioactive iodine
Answer is A. (Ref: KDT 6/e p249, 250) For the peripheral conversion of T4 to T3 the enzyme needed is 5'-deiodinase. It is inhibited by Propylthiouacil, Propanolol, Amiodarone.