Antithyroid medicine is often used for hyperthyroidism, because it works more quickly than radioactive iodine therapy. Radioactive iodine therapy destroys part or all of the thyroid gland, depending on the dosage used. But antithyroid medicine does not cause permanent thyroid damage.

You may take antithyroid medicine before you have radioactive iodine treatment or surgery—to bring your metabolism to normal, to make you feel better, or to reduce the chances of more serious problems.

Antithyroid medicine does control hyperthyroidism in many people. But the medicine does have some drawbacks.

• You have to take the medicine for at least 1 year.
• Your symptoms may come back after you stop taking it. And then you have to start taking antithyroid medicine again or try a different treatment.
• There are some rare side effects from the medicine, ranging from a rash to a low white blood cell count, which can make it hard for your body to fight infection.

Your doctor may prescribe additional medicines to treat symptoms caused by hyperthyroidism, such as rapid heartbeat or dry eyes. These medicines can help you feel better while you wait for another treatment to begin to work.

What to think about

• Antithyroid medicine may or may not make your hyperthyroidism permanently go away. The medicine is much more effective in people with mild disease. Up to 30 out of 100 people in the United States will have their hyperthyroidism go away (go into remission) after taking antithyroid medicine for 12 to 18 months.³
• Antithyroid medicine works best if you have mild hyperthyroidism, if this is the first time you are being treated for Graves' disease, if you are younger than 50, or if your thyroid gland is only swollen a little bit (small goiter). It is not used for thyroiditis.
• Antithyroid medicine is used instead of radioactive iodine if you are pregnant, breast-feeding, or trying to become pregnant.
• Children are treated with antithyroid medicine, because experts do not know if radioactive iodine treatment is safe for children. Treating children with antithyroid medicine is challenging. It is hard to know how much medicine they need when they are growing so quickly.
• Your doctor may prescribe low doses of thyroid hormone medicine to take with your antithyroid medicine so that your thyroid hormone levels do not get too low.

Hyperthyroidism: Should I Use Antithyroid Medicine or Radioactive Iodine?