Radioactive Iodine for Hyperthyroidism

Treatment Overview

Radioactive iodine is a medicine that you take one time. After you swallow it, it is taken up by your thyroid gland. Depending on the dosage used, the radioactivity in the iodine destroys most or all of the tissue in your thyroid gland, but it does not harm any other parts of your body.

While radiation can cause thyroid cancer, treatment of hyperthyroidism with radioactive iodine does not increase your chances of getting thyroid cancer.

Radioactive iodine treatment has been safely used on millions of people for more than 60 years.

What To Expect After Treatment

Most people don't feel different after treatment. But a few people may have nausea.

Within a few days after treatment, the radioactive iodine will leave your body in your urine and saliva. How long it takes will depend on your age and on the dose you received. Young people get rid of radioactive iodine faster than older adults. Drink plenty of fluids during this time to help your body get rid of the radioactivity.

Your doctor will give you written instructions. To avoid exposing other people to radioactivity, it is important to follow your doctor's instructions carefully. He or she will instruct you on how far to stay away from people, how long you need to sleep alone, and other ways to stay safe. You will be directed to avoid close contact, kissing, sex, and sharing cups, dishes, or utensils.

Some general recommendations include:^{footnote 1}

Keep your distance from other people, especially children and pregnant women.
Do not sit next to someone in a motor vehicle for more than 1 hour.
Avoid close contact, kissing, or sexual intercourse.
Sleep alone in a separate room.
Use separate towels, face cloths, and sheets. Wash these and your personal clothing separately for 1 week.
Flush the toilet twice after each use. Rinse the bathroom sink and tub thoroughly after you use them.

After you take your treatment, you may have follow-up exams every 4 to 6 weeks until your thyroid hormone levels return to normal.

Why It Is Done

Radioactive iodine has the best chance of permanently curing hyperthyroidism. Doctors often use it if your hyperthyroidism comes back after you have been treated with antithyroid medicine. It can also be used if your hyperthyroidism comes back after you have surgery to remove part of your thyroid gland.

How Well It Works

For most people, one dose of radioactive iodine treatment will cure hyperthyroidism. Usually, thyroid hormone levels return to normal in 8 to 12 weeks. In rare cases, the person needs a second or third dose of radioactive iodine.

Risks

Some side effects from radioactive iodine treatment include:

Metallic taste in your mouth.
Dry mouth.
Sore throat.
Neck pain. Radioactive iodine treatment can make your neck swell up or hurt.
Nausea or vomiting, which is usually mild.
Constipation or diarrhea.
Fatigue.
Unusually low (hypothyroidism) or unusually high (hyperthyroidism) thyroid levels.

If you have Graves' ophthalmopathy, it may get worse temporarily after radioactive iodine therapy.

What To Think About

Most people—depending on their ages, how much thyroid hormone their bodies make, and other health conditions they have—are treated first with radioactive iodine.

Radioactive iodine is often recommended if you have Graves' disease and are older than 50, or if you have thyroid nodules (toxic multinodular goiter) that are releasing too much thyroid hormone. Radioactive iodine is not used if:

You are pregnant or you want to become pregnant within 6 months of treatment.
You are breastfeeding.
You have thyroiditis or another kind of hyperthyroidism that is often temporary.

You may take antithyroid medicine for several weeks or months before treatment with radioactive iodine. The antithyroid medicine will lower thyroid hormone levels in your body and will also lower your chances of having a more serious problem called thyroid storm. You may also take additional medicines that can make you feel better and help your thyroid return to normal before you are given radioactive iodine.

Radioactive iodine has been used to treat hyperthyroidism for more than 60 years. There is no evidence that radioactive iodine causes cancer, infertility, or birth defects.

If you have had radioactive iodine treatment and you want to travel after treatment, prepare for any problems you may have at security checks. People who have had radioactive iodine treatment can set off the radiation detection machines.

If you plan to travel after your radioactive treatment:

Check with local authorities about special procedures or considerations.
Ask your doctor to write a letter describing the radiation isotope used, the date and time of treatment, the dose, and its biological half-life (how long it takes for half of the radioactive iodine to be eliminated from the body). The letter should include your doctor's 24-hour telephone numbers so that authorities can call your doctor if they need to verify the information in the letter.
Keep in mind that you will have to wait for permission to travel.

References

Citations

Sisson JC, et al. (2011). Radiation safety in the treatment of patients with thyroid diseases by radioiodine 131I: Practice recommendations of the American Thyroid Association. From the American Thyroid Association Taskforce on Radioiodine Safety. Thyroid, 21(4): 335–346.