Radioactive Iodine I-131 (also called Radioiodine I-131) therapy is a treatment for an overactive thyroid, a condition called hyperthyroidism. Hyperthyroidism can be caused by Graves' disease, in which the entire thyroid gland is overactive, or by nodules within the gland which are locally overactive in producing too much thyroid hormone.
Nuclear medicine imaging uses small amounts of radioactive material to diagnose, evaluate or treat a variety of diseases. These include many types of cancers, heart disease, gastrointestinal, endocrine or neurological disorders and other abnormalities. Because nuclear medicine exams can pinpoint molecular activity, they have the potential to identify disease in its earliest stages. They can also show whether a patient is responding to treatment.
The thyroid is a gland in the neck that produces two hormones that regulate all aspects of the body's metabolism, the chemical process of converting food into energy. When a thyroid gland is overactive, it produces too much of these hormones, accelerating the metabolism.
Radioactive iodine (I-131), an isotope of iodine that emits radiation, is used for medical purposes. When a small dose of I-131 is swallowed, it is absorbed into the bloodstream in the gastrointestinal (GI) tract and concentrated from the blood by the thyroid gland, where it begins destroying the gland's cells.
Radioactive iodine I-131 may also be used to treat thyroid cancer.
Any preparations needed?
- You should not eat or drink after midnight on the day of the procedure. If you have been taking anti-thyroid medications, you must stop at least three days before the therapy is given. Frequently, the anti-thyroid medication is stopped for five to seven days before therapy.
- • You will be able to return home following radioactive iodine treatment, but you should avoid prolonged, close contact with other people for several days, particularly pregnant women and small children. The majority of the radioactive iodine that has not been absorbed leaves the body during the first two days following the treatment, primarily through the urine. Small amounts will also be excreted in saliva, sweat, tears, vaginal secretions, and feces.
- If your work or daily activities involve prolonged contact with small children or pregnant women, you will want to wait several days after your treatment to resume these activities. Patients with infants at home should arrange for care to be provided by another person for the first several days after treatment. Your radiologist can be more specific for your given situation, but usually this time period is only two to five days.
- Your treatment team will give you a list of other precautions to take following your treatment with I-131. The following guidelines comply with the Nuclear Regulatory Commission:
- Use private toilet facilities, if possible, and flush twice after each use.
- Bathe daily and wash hands frequently.
- Drink a normal amount of fluids.
- Use disposable eating utensils or wash your utensils separately from others.
- Sleep alone and avoid prolonged intimate contact for three or four days. Brief periods of close contact, such as handshaking and hugging, are permitted.
- Launder your linens, towels, and clothes daily at home, separately. No special cleaning of the washing machine is required between loads.
- Do not prepare food for others that requires prolonged handling with bare hands.
- If you are breast-feeding, you must stop several days before to ensure that milk production has also stopped.
- You should avoid becoming pregnant from six months to one year after treatment.
- You must be sure you are not pregnant before receiving I-131. Many facilities require a pregnancy test within 24 hours prior to giving I-131 in all women of child-bearing age who have not had a surgical procedure to prevent pregnancy.
- Patients who need to travel immediately after radioactive iodine treatment are advised to carry a letter of explanation from their physician. Radiation detection devices used at airports and federal buildings may be sensitive to the radiation levels present in patients up to three months following treatment with I-131. Depending on the amount of radioactivity administered during your treatment, your endocrinologist or radiation safety officer may recommend continued precautions for up to several weeks after treatment.
- Radioiodine therapy is not used in a patient who is pregnant. Depending on the stage of pregnancy, I-131 given to the mother may damage the baby's thyroid gland. In such a case, discussion of the issue with the patient's physician is advised. When given to a nursing mother, radioactive iodine can reach a baby through her breast milk. Most physicians feel that this procedure should not be used in women who are breastfeeding unless they are willing to cease breastfeeding their newborn. Also, it is recommended that pregnancy be delayed until at least six to 12 months after I-131 treatment.
- Women who have not yet reached menopause should fully discuss the use of I-131 with their physician.
