Dear Mayo Clinic: I have had hyperthyroidism for just over one year, and medication does not seem to keep it in check. I do not want to have my thyroid removed. But I'm nervous about radioactive iodine treatment, which is what was recommended. Is it safe? What are the risks?
A: Radioactive iodine is a safe, proven and effective treatment for hyperthyroidism. It is not the best choice for everyone, however. Talk to your doctor about the pros and cons of all the available treatment options.
Your thyroid is a butterfly-shaped gland at the base of your neck. This gland produces hormones that affect every cell in your body. Hyperthyroidism is a condition in which your thyroid makes too much of the hormone thyroxine. This disorder can cause weight loss, rapid or irregular heartbeat, sweating, nervousness and irritability.
Several medical conditions can lead to hyperthyroidism. The most common is Graves' disease. From your description, it sounds like your condition may fit this disorder. In addition to affecting the thyroid gland, Graves' disease may have an impact on the tissues behind your eyes, a condition known as Graves' ophthalmopathy.
The options you mention—medication, radioactive iodine and surgery—are the three treatments currently available for hyperthyroidism. Each has risks and benefits.
Anti-thyroid medications generally bring thyroid hormone levels down to normal and reduce hyperthyroidism symptoms. However, due to significant side effects—including liver damage and a risk of low white blood cell counts—medications are not a long-term solution. Typically, they are used for no longer than about 18 months.
In about 30 percent of people who take anti-thyroid medication, hyperthyroidism does not return when the medication is stopped. For most, however, the disorder comes back within a few months. These individuals are then usually treated with either radioactive iodine or surgery.
Although the idea of putting something radioactive into your body may sound intimidating, iodine treatment has been shown to be safe and effective. It usually involves taking one dose by mouth. Because the thyroid is the only part of your body that takes up iodine, the radioactive iodine is absorbed only by that gland. The type of iodine used destroys the thyroid's ability to make thyroid hormone over the course of two to three months. Afterward, hyperthyroidism is eliminated. You then need to take thyroid replacement hormone for the rest of your life.
Several large studies have examined whether people who take radioactive iodine have a higher risk of cancer. No increase in cancer risk was found, even when people were followed over many years.
Radioactive iodine may not be appropriate if you have Graves' ophthalmopathy. Research has shown that radioactive treatment may make this condition worse, especially if you are a smoker.
If you have radioactive iodine treatment, you do need to take some precautions. The iodine not absorbed by your thyroid is eliminated through urine, sweat and saliva, so you need to be careful around other people. For about 48 hours after treatment, you should sleep in a bed separate from others. You should not share any eating utensils or drinking glasses. In addition, you have to stay at least six feet away from other people.
These precautions are not due to any proven risk to others. They are simply to keep the radiation away from people who do not need to be exposed to it.
Hyperthyroidism also can be eliminated by surgically removing the thyroid gland. Because several important nerves and other glands are near the thyroid, it is best to have the surgery done by a surgeon who is experienced and familiar with the procedure. It is definitely an operation that requires a specialist.
As you consider your options, discuss them with your doctor. Thoroughly talk through all your concerns and questions. After that, you should be able to make an informed choice that best fits your situation.
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