Radioactive Iodine (RAI)

RAI treatment works by destroying some or all of the thyroid tissue that is producing too much thyroid hormone. RAI is the only way to ablate parts of the thyroid gland without causing harm to other parts of the body. The technique relies on the fact that the thyroid gland is the only part of the body that takes up iodine.

Before RAI treatment, you will have an RAIU scan to confirm that you have hyperthyroidism and that the cause is not thyroiditis, which does not respond to RAI. Unlike the diagnostic scans, RAI uses a stronger radioactive isotope, namely iodine-131, instead of iodine-123. In patients who take up low levels of the RAI, a medication called Thyrogen may be used. Thyrogen is a synthetic version of TSH that has the same effect on thyroid cells — it encourages them to take up the RAI.


RAI treatment should never be used in women who are pregnant or nursing. And women who are trying to conceive should wait at least six months to a year after RAI before even trying to get pregnant.

The actual treatment is fairly simple. Beforehand, you may be asked to eat a low-iodine diet for a few weeks to ensure that other sources of iodine do not interfere with the RAI. The treatment is then given orally by pill or liquid in the nuclear medicine division of a hospital. The substance travels into the bloodstream, where it is picked up by the overactive disease cells in the thyroid. Once there, the RAI destroys the diseased thyroid tissue.

Precautions to Take

After treatment, though the amount of radioactivity is small, you may be advised to take precautions for the first week or two, so that your radioactivity does not contaminate others. The RAI is eventually excreted in the urine, and also in saliva and sweat. Here are some precautions to follow:

  • Drink a lot of water. The fluid will help flush the RAI from your body.

  • Avoid intimate contact with others, such as kissing and hugging, especially with small children and pregnant women.

  • Wash all glasses, utensils, and dishes immediately after use.

  • Flush toilets two or three times after each use.

  • Separate your clothes, linens, and towels from others'.

  • Sleep alone.

  • Avoid preparing food for others, if possible. If you must, wash your hands carefully beforehand.

  • Maintain a reasonable physical distance from other people.

Also, if you travel by plane shortly after RAI treatment, carry a letter from your doctor explaining your recent therapy. Some detection devices can be triggered by even the slightest amount of radiation.

Although highly effective, it will probably take a few months to know for sure whether the RAI has succeeded and for your symptoms to fade completely. During that time, you will undergo routine tests to measure the amounts of thyroid hormone in your blood.

In most people, RAI is highly successful and safe. The procedure, which has been in use since the 1950s, does not increase your risk for thyroid cancer, although most people become hypothyroid afterward.

Sometimes, finding the perfect dose of RAI can be very difficult. High doses of RAI are more likely to be successful, but almost guarantee that you'll be hypothyroid in the end. A lower, more conservative amount of RAI often doesn't work. Too little treatment, and you wind up still battling hyperthyroidism. In some cases, the RAI may make you euthyroid — meaning you have normal thyroid levels — fora year or so, before you develop hyperthyroidism again or hypothyroidism after that.


People who have severe thyroid eye disease caused by Graves' disease may not be good candidates for RAI. The treatments tend to cause a worsening of the eye symptoms. But if RAI is necessary, you may want to consider taking steroids, which seem to lessen the effects on the eyes.

For most people, a single treatment is sometimes all it takes to be cured of hyperthyroidism. About a third of all patients will need a second dose. And in rare cases, a third dose may become necessary. These numbers depend on the dose of RAI used.

Side Effects

After treatment, you may notice some pain or tenderness in the neck, which can be treated with over-the-counter pain remedies. Some people may experience nausea or vomiting, especially if they've received a higher dose. You may notice some dryness in the mouth and a decrease in the production of saliva. Eating sour candies, lemons, or pickles can sometimes stimulate the salivary glands and eliminate the dryness.

In some cases, patients may experience an increase in their symptoms of hyperthyroidism. This development is caused by the death of the diseased cells, which are spilling thyroid hormone into the bloodstream. This side effect is more problematic in older adults, who may have heart problems as a result. Treatment with antithy-roid drugs or other medications can usually relieve the symptoms. Fortunately, this is typically a temporary situation that disappears as the cells die off for good.


Former Olympic gold medalist Gail Devers had RAI treatments for her hyperthyroidism from Graves' disease. Before winning the gold medal in the 100-meter dash in 1992, Devers's condition was so severe that doctors had considered amputating her feet, which had become blistered and swollen. Fortunately, a correct diagnosis was made in time for treatment — and future Olympic success. She won gold again in the same event in 1996.

Some people may experience temporary bouts of hypothyroidism in the six months after RAI treatment and then become euthyroid. But many people who undergo RAI become permanently hypothyroid. In fact, research suggests that as many as 50 percent of all people who undergo RAI will develop hypothyroidism. The risk rises with each successive treatment. That's why it's important to get routine thyroid function tests if you've received RAI. Joan, for example, recalls the pendulum of being first hyperthyroid and then becoming hypothyroid about six weeks after her thyroid was “killed.”

Before she had RAI, Joan was eating constantly — and still losing weight. She was also extremely exhausted and learned that her heart rate was at a staggering high of 120 beats per minute. But after RAI, the weight started creeping back. Fatigue set in, and she felt achy. Sure enough, a TSH test showed that her levels were high. Her doctor put her on Synthroid, and her symptoms disappeared. She considers herself very lucky.

Although the prospect of becoming hypothyroid for life may seem unappealing, the alternative — not treating your overactive thyroid — is highly bothersome and potentially life-threatening. Keep in mind, too, that hypothyroidism is considerably easier to treat than hyperthyroidism is. The only challenge might be finding the right dosage, a process that may take some time and trial and error.

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