Patient education: Radioiodine treatment for hyperthyroidism (The Basics)

What is radioiodine treatment? — 

Radioiodine, also called "radioactive iodine," is a treatment for hyperthyroidism. Hyperthyroidism is when the thyroid gland makes too much thyroid hormone (figure 1). It is sometimes called an "overactive thyroid."

Radioiodine destroys the overactive part of the thyroid gland. It takes 3 to 4 months to work.

The treatment can cause the thyroid to make too little thyroid hormone, a condition called hypothyroidism. If you have hypothyroidism, you need to take thyroid hormone medicine for the rest of your life.

How do I prepare for radioiodine treatment? — 

The doctor or nurse will tell you if you need to do anything special to prepare. Before the procedure, your doctor will do an exam and also check that you are not pregnant or breastfeeding. They might send you to get:

●Lab tests

●Thyroid uptake tests

Your doctor will also ask you about your "health history." This involves asking you questions about any health problems you have or had in the past, past surgeries, and any medicines you take. Tell them about:

●Any medicines you are taking – This includes any prescription or "over-the-counter" medicines you use, plus any herbal supplements you take. It helps to write down and bring a list of any medicines you take, or bring a bag with all of your medicines with you.

●Any allergies you have

Before you receive radioiodine, the doctor might recommend:

●Starting medicines to help control hyperthyroidism symptoms – Some medicines need to be taken for several weeks before radioiodine treatment and then stopped a couple days before the treatment. Other medicines are started after radioiodine.

●Stopping any supplements that contain iodine supplements, including most multivitamins

Ask the doctor or nurse if you have questions or if there is anything you do not understand.

What happens during radioiodine treatment? — 

Radioiodine comes as a pill or liquid you swallow. The thyroid gland absorbs or takes in the radioiodine immediately. Over the next 2 to 4 months, the radioiodine damages the thyroid gland so that it makes less thyroid hormone.

What happens after radioiodine treatment? — 

Most people can go home after treatment.

Most of the radioiodine will leave your body over the next week or so. There are things you can do to keep others safe during this time. Your doctor or nurse will tell you exactly what you need to do and for how long. The timing depends on the dose you were given.

You might need to:

●Avoid sharing cups or utensils. Use gloves, or avoid preparing food for others.

●Avoid pregnant people and children. Do not hold small children on your lap.

●Avoid sleeping in the same bed with anyone.

●Avoid sexual activity until your doctor says that it is OK.

●Use a separate bathroom from other people in your home, if possible. Men should sit down when using the toilet. Flush the toilet with the lid closed after each time that you use it. Wash your hands well.

●Avoid close contact with other people, including crowds.

●Avoid trips on public transportation or airplanes. If you need to travel, carry a letter that explains your treatment. Radiation detection devices at airports or federal buildings might pick up small amounts of radiation from you.

You should also:

●Take all of your medicines and have follow-up testing as instructed.

●Follow your doctor's advice on how much fluid to drink.

●Take a shower each day, and wash your hands often.

●Use reliable birth control for the next few months if you could get pregnant or get a partner pregnant.

What are the risks of radioiodine? — 

Your doctor will talk to you about all of the possible risks, and answer your questions. Possible risks include:

●Hypothyroidism

●New or worsening thyroid eye disease

●Feeling tired

●Thyroid pain

●Thyroid cancer or other cancers

What if I want to get pregnant? — 

If you are pregnant or trying to get pregnant, do not get radioiodine treatment. The amount of radiation is small, but it can damage a developing baby's thyroid gland. You should also not get radioiodine treatment if you are breastfeeding.

If you were treated with radioiodine, wait at least 4 to 6 months before you start trying to get pregnant. This will give your doctor enough time to find out if your thyroid is making enough thyroid hormone after the radioiodine treatment. If the treatment causes your thyroid to make too little thyroid hormone, you will need to take thyroid hormone pills. It is important to have a normal amount of thyroid hormone in your body before getting pregnant.

Your doctor will check your thyroid hormone levels often during pregnancy. They must be at the right level during pregnancy to avoid risks to both you and your baby.

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