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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.
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:1
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.
Some side effects from radioactive iodine treatment
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
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
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:
Complete the special treatment information form (PDF)special treatment information form (PDF)(What is a PDF document?) to help you understand this treatment.
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.
June 10, 2013
E. Gregory Thompson, MD - Internal Medicine & David C.W. Lau, MD, PhD, FRCPC - Endocrinology
How this information was developed to help you make better health decisions.
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