Radioactive Iodine Therapy

Radioactive Iodine Therapy (RAI) is a medical treatment that uses a special form of iodine to treat an overactive thyroid gland (hyperthyroidism) or certain types of thyroid cancer. You take it by mouth, and it works by targeting and destroying specific thyroid cells, while largely sparing other body cells. This therapy is usually very effective.

What is Radioactive Iodine Therapy?

Radioactive Iodine Therapy (RAI), also known as radioiodine therapy, is a nuclear medicine treatment that uses a small, safe dose of radioactive iodine (I-131) to treat specific thyroid conditions. This special iodine is taken by mouth and absorbed by the thyroid gland, where it emits radiation to destroy overactive or cancerous thyroid cells.

Your thyroid gland, a butterfly-shaped organ in your neck, naturally absorbs iodine from your diet to make thyroid hormones. Radioactive iodine (I-131) is a form of iodine that has been made radioactive. When you take it, your thyroid cells absorb it just like regular iodine. Once inside the thyroid cells, the radioactive iodine releases radiation. This radiation damages and destroys the overactive or cancerous thyroid cells. Because only thyroid cells absorb iodine in significant amounts, the treatment mostly affects the thyroid gland, limiting harm to other parts of your body. RAI is typically given as a single dose, either as a capsule or a liquid. It is a targeted therapy, meaning it specifically seeks out and treats the problem cells in your thyroid.

Why it's done

Radioactive Iodine Therapy is primarily used to treat an overactive thyroid gland (hyperthyroidism), especially due to Graves' disease or toxic nodules. It is also a common treatment after surgery for certain types of thyroid cancer, such as papillary or follicular thyroid cancer, to destroy any remaining thyroid tissue or cancer cells.

One main reason for RAI is to treat hyperthyroidism, a condition where your thyroid gland makes too much thyroid hormone. This can happen with Graves' disease, an autoimmune condition, or with toxic nodules (growths in the thyroid). RAI helps by reducing the number of thyroid cells, which in turn lowers the amount of thyroid hormone produced. For people with thyroid cancer, RAI is often used after surgery to remove the thyroid gland. Even after surgery, tiny thyroid cells or cancer cells might remain in the body. The radioactive iodine targets and destroys these remaining cells, reducing the chance of the cancer coming back or spreading. Your doctor will determine if RAI is the right treatment for your specific condition, considering factors like your overall health, the type and stage of your thyroid cancer, or the severity of your hyperthyroidism.

How to prepare

Preparing for Radioactive Iodine Therapy involves several important steps to make the treatment most effective and safe. You will likely need to follow a low-iodine diet for one to two weeks before the procedure and stop certain thyroid medications. Women who are pregnant or breastfeeding cannot receive RAI, so a pregnancy test is required.

A crucial part of preparation is following a low-iodine diet for about one to two weeks before your treatment. This diet helps your thyroid cells become "hungry" for iodine, making them more likely to absorb the radioactive iodine effectively. You will need to avoid foods rich in iodine, such as seafood, dairy products, and iodized salt. Your doctor will also instruct you to stop taking certain medications. This might include anti-thyroid drugs (like methimazole or propylthiouracil) for several days, or thyroid hormone replacement medications (like levothyroxine) for several weeks. Stopping these medicines helps increase your body's thyroid-stimulating hormone (TSH) levels, which encourages thyroid cells to absorb more iodine. It is essential to tell your doctor about all medications, supplements, and herbal remedies you are taking. Women of childbearing age will need a pregnancy test before treatment, as RAI is not safe during pregnancy or breastfeeding. You will also receive specific instructions on how to prepare your home for the isolation period after treatment.

What happens during

During Radioactive Iodine Therapy, you will receive a single dose of radioactive iodine, usually as a capsule or a liquid that you swallow. This is typically an outpatient procedure, meaning you go home the same day. After taking the dose, the radioactive iodine begins to be absorbed by your thyroid cells, starting the treatment process.

On the day of your treatment, you will go to a specialized clinic or hospital department. A trained clinician will give you the radioactive iodine. It is usually a small capsule, similar to a vitamin pill, or a clear liquid that you drink. The dose is carefully calculated for your specific condition. The process of taking the medication itself is quick and painless. You will be given instructions on how to handle the capsule or liquid safely. After you swallow the dose, the radioactive iodine travels through your bloodstream to your thyroid gland. Because you will be emitting radiation for a period after treatment, you will receive detailed instructions on radiation safety precautions to follow at home. In rare cases, especially with very high doses for cancer, you might need to stay in the hospital for a short time until your radiation levels drop to a safe limit.

Recovery & timeline

After Radioactive Iodine Therapy, you will need to follow strict radiation safety precautions, usually for several days to a few weeks, to protect others from radiation exposure. You will likely need to limit close contact with family, especially children and pregnant women. Most people develop an underactive thyroid (hypothyroidism) and require lifelong thyroid hormone replacement medication.

The most important part of recovery is following the radiation safety guidelines provided by your medical team. For a period, typically ranging from a few days to two weeks depending on the dose, you will need to avoid close, prolonged contact with other people, especially children and pregnant individuals. You may need to sleep in a separate bed and use separate towels and eating utensils. You will also be advised to flush the toilet twice after each use, wash your laundry separately, and avoid public places or prolonged travel in enclosed spaces with others. These precautions help ensure that the small amount of radiation you emit does not affect those around you. Your doctor will tell you exactly when it is safe to resume normal activities. For most people treated for hyperthyroidism, and often for those treated for thyroid cancer, the RAI treatment will eventually lead to an underactive thyroid gland (hypothyroidism). This means your thyroid will no longer produce enough hormones. This condition is easily managed with daily thyroid hormone replacement medication, which you will likely take for the rest of your life. Regular follow-up appointments and blood tests will be necessary to monitor your thyroid hormone levels.

Risks & side effects

While generally safe and effective, Radioactive Iodine Therapy can cause some temporary side effects, such as neck pain, nausea, and changes in taste or dry mouth. Less commonly, it can affect salivary glands or tear ducts. The risk of developing other cancers later in life is very small and not clearly proven, with benefits usually outweighing these rare concerns.

Many people experience mild, temporary side effects after RAI. These can include tenderness or pain in the neck where the thyroid gland is located, mild nausea, and fatigue. Some individuals report changes in their sense of taste or a metallic taste in their mouth, which usually resolves within a few weeks. Because salivary glands and tear ducts can also absorb small amounts of iodine, some people may experience dry mouth (xerostomia) or dry eyes. Chewing gum or sucking on hard candies can help stimulate saliva production. Rarely, salivary glands can become swollen or painful. A very small, theoretical risk of developing other cancers, such as leukemia or stomach cancer, later in life has been discussed in some studies, but there is no clear evidence of a significant increase in risk. The benefits of treating hyperthyroidism or thyroid cancer with RAI generally far outweigh these extremely rare and unproven long-term risks. Your doctor will discuss all potential risks with you.

Success rate

Radioactive Iodine Therapy has a high success rate for treating hyperthyroidism, often resolving the condition with a single dose. For thyroid cancer, it is highly effective in destroying remaining thyroid tissue and microscopic cancer cells after surgery, significantly improving long-term outcomes and reducing the chance of recurrence.

For hyperthyroidism, RAI is highly effective. About 8 out of 10 people (80%) with Graves' disease achieve normal thyroid function or develop hypothyroidism after a single dose of RAI. For those who don't respond fully, a second dose can be given after several months. The goal is often to induce hypothyroidism, which is easier to manage than hyperthyroidism. In the treatment of thyroid cancer, especially papillary and follicular types, RAI is very successful as an "adjuvant" therapy, meaning it's given after the main treatment (surgery). It effectively destroys any remaining normal thyroid tissue and microscopic cancer cells that might not have been removed during surgery. This significantly reduces the risk of the cancer coming back (recurrence) and improves survival rates. The success of RAI depends on several factors, including the specific condition being treated, the dose of iodine given, and individual patient characteristics. Your medical team will monitor your progress with blood tests and scans to ensure the treatment has been effective and to manage any resulting hypothyroidism.

Frequently asked questions

How long does the radiation stay in my body after RAI?

Most of the radioactive iodine leaves your body within a few days to a week through urine, sweat, and saliva. However, you will need to follow radiation precautions for a longer period, typically several days to two weeks, as advised by your doctor, to protect others from residual radiation.

Can I be around children or pregnant women after RAI?

No, you must strictly avoid close or prolonged contact with children and pregnant women for the duration specified by your doctor, usually several days to two weeks. This is crucial to protect them from radiation exposure.

Will I lose my hair after radioactive iodine therapy?

Temporary hair thinning or loss is a rare side effect of radioactive iodine therapy, but it is not common. If it occurs, hair usually grows back within a few months.

Do I need to stay in the hospital for radioactive iodine therapy?

Most people receive radioactive iodine therapy as an outpatient procedure and go home the same day. Hospitalization is rare and usually only required for very high doses of RAI, where radiation levels need to be monitored closely.

Will I need to take medication for the rest of my life after RAI?

Yes, for most people treated with RAI for hyperthyroidism or thyroid cancer, the treatment leads to an underactive thyroid (hypothyroidism). This requires lifelong daily thyroid hormone replacement medication to maintain normal body functions.

Can I get pregnant after radioactive iodine therapy?

Women are advised to avoid pregnancy for at least 6 to 12 months after radioactive iodine therapy. This allows the radioactive iodine to clear from your body and ensures your thyroid hormone levels are stable before conception.

Sources

• MedlinePlus — Radioactive Iodine Therapy
• Mayo Clinic — Radioactive Iodine Therapy
• Cochrane Library — Radioactive Iodine Therapy