Radioactive Iodine Treatment for Thyrotoxicosis
The radioactive form of iodine (I-131) has been used for 40 yrs. to treat hyperthyroidism. Since iodine is a natural substance your thyroid uses to make thyroid hormones, radioactive iodine (RAI) is collected by your thyroid gland in the same way as non-radioactive iodine. Since the thyroid gland is the only area of the body that uses iodine, RAI does not travel to any other areas of the body, and the RAI that is not taken up by thyroid cells is eliminated from your body, primarily in urine. It is therefore a safe and effective way to treat your thyroid condition.
It is important that pregnant women never receive RAI for any reason because it will affect and may even destroy the developing foetus’ thyroid. You must not breast feed your child after treatment with RAI. You should wait at least 6, but preferably 12 months, before attempting to get pregnant after receiving a therapy dose of RAI. If you are planning to have a baby, you should discuss your situation with your doctor. Although RAI can pose a risk to your baby’s thyroid, radioactive iodine does not cause infertility or other birth defects.
Thyroid Function Testing
Before being treated for your thyroid condition you will have had a radio-nuclide thyroid scan. This scan provides information not only about the shape and size of the thyroid gland, but also about its function. When used to test thyroid function, only a very small amount of the radioactive substance is used so that the thyroid gland is not damaged and normal thyroid function is not affected.
Your thyroid scan used technetium-99m (Tc99m). If the Tc99m was avidly taken up by the thyroid gland, then the thyroid gland is considered to be “hot” or overactive. If the Tc99m was not taken up well then the thyroid is called “cold” or under-active. However, in some cases, the results can be confusing. For example, if you have hyperthyroidism, your thyroid may appear “cold” on the scan if you have thyroiditis or inflammation of the thyroid gland. This is because the thyroid gland is affected by this inflammation, resulting in an overabundance of thyroid hormones into your blood stream. Due to this inflammation the thyroid will not take up the radionuclide, thus the thyroid will appear “cold” on the scan even though you have hyperthyroidism.
Treatment for Graves’ disease
When used to treat Graves’ disease, instead of being used to make thyroid hormones, the radioactive iodine decreases the function of the hyperactive thyroid tissue by destroying the thyroid cells. A single dose of radioactive iodine is given as a capsule in order to treat hyperthyroidism. RAI is about 90% effective in curing the condition. For the additional 10% a second dose of radioactive iodine is needed. Only a few people fail this second dose and require surgery to remove the overactive thyroid gland.
Radioactive iodine takes several months in order to have its full effect, although symptoms should definitely improve after about 6 weeks.
However, because it is impossible to give just the right amount of radioactive iodine to destroy the exact amount of thyroid gland, enough to cure the hyperthyroidism, but not enough to cause hypothyroidism, the eventual result is usually an under-active thyroid. This hypothyroidism may not occur for years because there may be a small amount of over functioning thyroid tissue after treatment. Eventually this overactive remnant will burn out and you will be left with a deficiency of thyroid hormones.
A possible short term side effect of RAI treatment is a feeling of nausea. If you vomit after treatment please contact us immediately In addition, some of the RAI may be picked up by the salivary glands around the jaw and under the tongue, causing some swelling and enlargement of these glands. This is treated by drinking plenty of fluids and sucking on lemon drops or similar lollies (in order to stimulate the flow of saliva) and occasionally pain medicine like aspirin.
It takes a few weeks after the treatment dose of radioactive iodine is given before there is a decrease in the blood level of the thyroid hormones. During the first week or two after the treatment the level of thyroid hormones in your blood stream may actually increase due to the action of the RAI on the thyroid gland. In many people this increased period of hyperthyroidism may not be a problem. However for some patients, especially those with known heart conditions, this period may put them at risk because the excess of thyroid hormones may over-stimulate the heart. For this reason, many practitioners prescribe anti-thyroid drugs and/or beta-blockers for their patients who are about to undergo RAI in order to prevent this thyroid “storm”.
- You may travel home by public transport providing the journey is less than 1 hour.
- You may travel home by private transport with a maximum of one other person in the car. You may drive yourself. If you are travelling with someone else please ensure that you are seated diagonally opposite the other person.
- For the first week after treatment please avoid using public transport. If you must use public transport in the first week after treatment ensure that no journey is longer than 1 hour.
- It is advisable that you make arrangements to sleep apart from your partner for 7 days. If your partner is pregnant then you should sleep apart for a minimum of 21 days.
- Close contact with pregnant women should be avoided for 21 days after treatment.
- Close contact with children less than 4 years of age should be avoided for 14 days after treatment.
- Close contact with children aged 4-18 years should be avoided for 3 days after treatment.
By close contact we mean a distance of 1 metre or less. It is safe to be in the same room as children, but do not hold them close to you or sit next to them for long periods, e.g. for more than 1 hour. Do not let your children sleep with you.
- Double flush the toilet for 7 days after treatment.
- All your clothing used during the first 7 days after treatment should be stored and washed separately in your washing machine.
- Increase your fluid intake and empty your bladder frequently for 7 days after treatment.
- Avoid places of entertainment for 7 days after treatment.
- You should not return to work for 7 days after treatment.
- If you work with small children or pregnant women you should not return to work for 21 days after treatment.
- Avoid pregnancy, and fathering children for at least 6 months, preferable for 12 months afer treatment with RAI.
- If you are breast feeding your child, this must be stopped after treatment with RAI.
Please contact us if you require any further information with regard to the radiation aspects of your treatment. Please contact your referring doctor for any other queries.