Radioactive Iodine therapy

What is radioactive iodine therapy?

Radioactive iodine therapy gives you a dose of iodine that has been made radioactive, which then destroys an overactive thyroid gland or certain thyroid cancers, while leaving the rest of your body largely untouched. You take the dose as a drink or a swallowed capsule, and your thyroid draws it in because iodine is what your thyroid normally uses to make its hormones.

What conditions does it treat?

Doctors use radioactive iodine therapy for two main groups of thyroid conditions:

• an overactive thyroid gland (hyperthyroidism), most often caused by Graves' disease or by overactive thyroid nodules
• papillary or follicular thyroid cancer, including cases where the cancer has spread to other parts of your body.

What are the benefits of radioactive iodine therapy?

Radioactive iodine works well because it targets thyroid tissue specifically, with little effect on the rest of your body's cells. It is a very successful treatment for people with an overactive thyroid.

For thyroid cancer, the treatment can destroy cancer cells even if they have spread beyond your neck, and doctors can give further doses every few months if scans show cells remain.

Are there different types of treatment?

There is no surgery involved. Instead, radioactive iodine comes as a drink that tastes like water, or as a capsule you swallow with water; occasionally it is given by injection into a vein.

If you are being treated for an overactive thyroid, this is usually a single outpatient dose and you go home the same day. If you are being treated for thyroid cancer, the dose is larger, so a short hospital admission of a few days is common.

How do you prepare for radioactive iodine therapy?

Your healthcare team talks you through how to prepare, usually starting at least a few weeks beforehand:

• blood tests to check your thyroid hormone levels
• following a low-iodine diet for one to two weeks beforehand: fresh meat, vegetables, rice, pasta and most oils are fine, milk, cheese, butter and eggs are limited to small amounts, and fish, seafood, iodised salt and takeaway meals are avoided
• either an rhTSH injection given once a day for two days running, or coming off your thyroid hormone tablets for a few weeks beforehand, both ways of raising a hormone (TSH) that helps your thyroid take up the iodine
• if you are being treated for an overactive thyroid, pausing thyroid-suppressing medicines (propylthiouracil and carbimazole are two examples) roughly a week beforehand
• a pregnancy test if there is any chance you could be pregnant, since this treatment is not safe during pregnancy
• anti-sickness medication shortly before your dose, to help prevent nausea.

What happens during the procedure?

1. You have blood tests to check your thyroid hormone levels, then collect your dose and any other medication from the hospital pharmacy.
2. You may be given an anti-sickness tablet around half an hour beforehand.
3. A doctor or physicist explains the radiation safety precautions you will need to follow, and answers any questions.
4. You swallow the radioactive iodine as a drink or capsule, or occasionally receive it by injection; this part takes only a few minutes.
5. You stay in a treatment room or single hospital room while staff measure your radioactivity every so often. For lower doses this is often done in about three hours, though it can take longer, and it may mean a stay of a few days in hospital if you are being treated for thyroid cancer.
6. Once your radioactivity has fallen to a safe level, you are given detailed instructions and can go home.

What does recovery look like?

While you are in hospital, staff check your radioactivity levels regularly and may ask you to stay in a single room, particularly if you have had a higher dose for thyroid cancer. You will not be able to have close contact with children or pregnant visitors during this time, and you will be asked to flush the toilet twice and shower daily to help wash away any radioactivity.

Once home, you will need to keep some distance from other people for a period that depends on your dose, generally a few days for an overactive thyroid and potentially longer after treatment for thyroid cancer. This can include sleeping alone, avoiding public transport, cinemas or restaurants, and staying an arm's length or more from others. You will also need to wash your laundry, towels and dishes separately for the first few days.

Your team will confirm exactly how long these precautions apply to you and will give you a card to carry, which is also useful if you are travelling through airport security within the next few months. You will usually have a follow-up appointment around six weeks after your dose, along with regular blood tests to check how your thyroid is responding.

What are the risks and complications?

Most people have few or no side effects, but possible risks and after-effects include:

• neck discomfort, swelling, a dry mouth, salivary gland swelling or taste changes in the days after treatment
• mild sickness, or discomfort in your thyroid a bit like a sore throat, and inflammation of your stomach lining
• an underactive thyroid needing lifelong hormone replacement tablets, which is a common and expected long-term effect rather than a rare complication
• temporarily lower sperm count or irregular periods, usually settling within one to two years
• a small increased long-term risk of stomach cancer, leukaemia, cancer of the salivary glands, or (if treated for an overactive thyroid) thyroid cancer, though all of these are rare
• worsening of thyroid eye disease if you have Graves' disease, which your doctor may treat with a short course of steroids.