Antithyroid medications are a class of drugs primarily used to treat hyperthyroidism, a condition in which the thyroid gland overproduces the hormones triiodothyronine (T3) and thyroxine (T4). These hormones regulate metabolism, heart rate, and body temperature, so excess levels can cause significant health issues.

The main goal of antithyroid therapy is to restore normal thyroid function (euthyroidism) by reducing hormone synthesis. This is especially important in autoimmune disorders like Graves’ disease, where antibodies stimulate the thyroid to produce more hormones. Antithyroid drugs are often the first-line treatment, particularly in younger patients and those with mild to moderate disease.

There are two main medications in this class:

•Methimazole (MMI) – the most commonly used due to better efficacy and safety profile

•Propylthiouracil (PTU) – reserved for specific situations, like early pregnancy or thyroid storm

These medications are usually prescribed as long-term therapy (12–18 months) to achieve remission or as a bridge to definitive treatments such as radioactive iodine therapy or surgery.