Mechanism of Action Antiroid Tab, Propylthiouracil (PTU) is an antithyroid medication primarily used to manage hyperthyroidism. It works by inhibiting the enzyme thyroperoxidase, which plays a crucial role in the synthesis of thyroid hormones (T3 and T4). By blocking this enzyme, PTU reduces the production of thyroid hormones, thereby decreasing their levels in the blood. Additionally, PTU inhib..