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.
Radioactive iodine treatment has been safely used on millions of people for more than 60 years.
Within a few days after treatment, the radioactive iodine will leave your body in your urine. Drinking plenty of fluids during this time will help your body get rid of the radioactivity. To avoid exposing other people to radioactivity, it is important to take the following precautions for the first 5 days after your treatment:
To further reduce the chance of exposing other people to radioactivity:
After you take your treatment, you may have follow-up exams every 4 to 6 weeks until your thyroid hormone levels return to normal.
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.
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.
For some people, radioactive iodine treatment causes the thyroid gland to become swollen and inflamed (radiation thyroiditis). If this happens, you may feel pain in your neck. Or your hyperthyroidism may temporarily get worse. If you get radiation thyroiditis, it usually does not last more than a few days. And you can take medicines that will help you feel better.
Radioactive iodine treatment may cause hypothyroidism, which means your body makes too little thyroid hormone. Most people will have hypothyroidism within a year after treatment. If you have hypothyroidism, you will need to take thyroid hormone medicine for the rest of your life. For more information, see the topic Hypothyroidism.
If you have Graves' ophthalmopathy, it may get worse temporarily after radioactive iodine therapy.
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 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 within a few days after treatment, prepare for any problems you may have at airport security. People who have had radioactive iodine treatment can set off the radiation detection machines in airports.
If you plan to travel within 5 to 7 days of your radioactive treatment:
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