Radioiodine (sodium I-131) is a form of radiation therapy that has been used for many years to treat thyroid conditions. It is safe and effective but requires you to observe certain precautions to decrease the small amount of radiation that other people may receive from your body and bodily fluids. Show
How long does the radioiodine stay in your body?Radioiodine stays in your body for only a short time. Most of the radioiodine that does not go to thyroid tissue will be eliminated from your body during the first few days after treatment. Radioiodine leaves your body primarily through your urine, but very small amounts can be found in your saliva, sweat and bowel movements. Ask your doctor for more information. You also may get more information from the Society of Nuclear Medicine and Molecular Imaging at www.snmmi.org. How can you reduce radiation exposure to others?Radiation exposure to other people can be reduced by keeping a reasonable distance between yourself and others and keeping the time you are close to others to a minimum. Your doctor should review the following instructions with you and answer all of your questions. It is important to let your doctor know if you will not be able to follow all of these instructions. These instructions apply if you are returning to your own home after treatment using private transportation. You should ask your doctor for additional instructions if you are planning to use public transportation or stay in a hotel or other non-private lodging. First 8 hours:
First two days:
First week:
Additional instructions for women who are breastfeedingYou must stop breastfeeding before you can be treated with radioiodine. If possible, you should stop breastfeeding for 6 weeks prior to treatment. You should not resume breastfeeding after treatment for your current child, but you may safely breastfeed babies you may have in the future. Failure to follow this guidance may result in permanent damage to the thyroid gland of the nursing infant or child. PregnancyRadioiodine treatment should not be given during pregnancy. Tell your doctor if you are pregnant or could be pregnant. If you are planning to become pregnant, you should wait at least 6 months after treatment to ensure your thyroid hormone level is normal and that you do not need additional treatment. Consult your doctor. Other things you should know during the first week after treatment:Small amounts of radiation from your body may trigger radiation monitors at airports, border crossings, government buildings, hospitals, and waste disposal sites for up to 3 months after treatment. Ask your doctor for advice if you will be in these areas. Your doctor can provide you with a letter describing your medical treatment if you cannot avoid these areas. Discarded items that are heavily stained with urine, saliva, nasal secretions, sweat or blood may trigger alarms at waste disposal sites. Ask your doctor for advice on how to safely dispose of these items. This information may be used to meet the requirements of the U.S. Nuclear Regulatory Commission for giving written instructions to patients following treatment with radioiodine.More specific instructions may be required in certain circumstances. Radioiodine is given as a pill to treat hyperthyroidism by gradually shrinking your thyroid—ultimately destroying the gland. Traditionally, this treatment has been known as radioactive iodine therapy; but the newer term radioiodine, or RAI, was introduced to make the therapy sound less scary. For this discussion, we’ll be using the term radioactive iodine therapy. Radioactive iodine therapy is the most commonly used hyperthyroid treatment in the U.S., and it’s actually much safer than it sounds. It is also a more reliable cure for hyperthyroidism than antithyroid medications: Unlike these drugs, radioactive iodine is permanent. What Is Radioiodine Ablation?Radioactive iodine therapy can destroy either all or part of your thyroid gland, depending on what is needed to alleviate your hyperthyroid symptoms. In some cases, it is not necessary to have the entire thyroid gland rendered nonfunctional. In most cases, though, the whole gland will need to be destroyed. Your doctor may refer to radioactive iodine therapy as radioactive iodine ablation or radioiodine ablation. Ablation is a term that refers to destruction or erosion. This article will focus on what you might expect when you are faced with the total elimination of your thyroid gland and its key functions. First Step: Radioactive Iodine Therapy TestDepending on the dose, radioactive iodine can kill a portion, or all, of your thyroid. Your doctor will order a radioactive iodine uptake and scan to determine the dose you will need, the cause of your hyperthyroidism, and other information about your thyroid tissue. In this test, you will ingest a very small dose of radioactive iodine. Your doctor will observe your thyroid's activity level by measuring the amount of iodine it absorbs. He or she will do this using a scan of your thyroid, which will show the healthy and diseased tissues. In determining the best dose, the size of the thyroid gland (determined by a physical exam) and results of the uptake test are the two most important factors. The larger the gland, the larger the radioactive iodine dose. The higher the iodine uptake, the smaller the dose. How Radioactive Iodine WorksRadioactive iodine is available in an oral pill, so you won't need to be hospitalized. After you take the pill, your doctor will recommend drinking lots of fluids to prompt the release of the radioactive iodine through your urine. Fortunately, radioactive iodine therapy is targeted to treat only your thyroid gland. Thyroid cells are the main cells in the body that can absorb iodine, so there is very little radiation exposure to the rest of your body's cells. When the thyroid cells absorb the radiation, they are damaged or destroyed. Approximately 90% of patients need only one dose before they are cured of their hyperthyroidism. Though you may only need a single dose, it may take up to six months before the medication fully destroys all or part of the thyroid. Fortunately, most patients experience reduced symptoms about a month after treatment. If your symptoms persist 6 months after treatment, you may need a second dose. In the rarest of cases, some patients will not benefit from a second dose and may instead require surgery. Side Effects of Radioactive IodineThe most common side effect of radioactive iodine may seem ironic, yet it makes perfect sense—hypothyroidism. The radioactive iodine often kills an excessive amount of thyroid cells, leaving the thyroid unable to produce enough hormones—the opposite problem you had before. It might seem odd to replace one disorder with another, but hypothyroidism is much easier to treat on a long-term basis than hyperthyroidism. If you develop hypothyroidism, you will need to take life-long thyroid hormone replacement therapy , but it is a safe, reliable, and cost-effective treatment. Other side effects of radioactive iodine include:
Note: Don't let your fears about radiation give you the wrong impression about this therapy. Radioactive iodine used in this manner will not cause thyroid cancer or impair fertility. A Special Caution for WomenPregnant women or women who want to become pregnant in the next 6 months should not use radioactive iodine, as the treatment can destroy the fetus's thyroid and impair its development. In fact, women should wait a year before conceiving if they have been treated with the therapy. Women who are breast-feeding should also not use radioactive iodine. After TreatmentIn the days following radioactive iodine therapy, you will need to take certain precautions to prevent radiation exposure to others. Keep in mind that the precautions listed below are general, and your doctor will be more specific about how many days and what kinds of precautions you need to follow tailored to your individual needs and medical circumstances.
Notes: This article was originally published October 14, 2009 and most recently updated February 5, 2020. |