What is Radioactive Iodine?

In science fiction movies, things that are radioactive almost always cause trouble. But in real life, doctors can use some of them to help people. Radioactive iodine is a good example.

Ordinary iodine is one of the basic nutrients our bodies need, and we get it through food. The thyroid, a gland in the neck, uses it to make a hormone that guides some of the body’s essential functions, such as growth and physical development.

Doctors use a different form of it: radioactive iodine. A substance that’s radioactive gives off a form of energy so intense that it’s capable of harming the body. But doctors have harnessed that power. When someone gets a small dose of radioactive iodine, scanners can pick it up, and it can help reveal certain illnesses. Larger doses can attack thyroid cancer, prostate cancer, and other diseases.

How Does It Work?

When you get a dose of radioactive iodine in liquid capsule form, your thyroid gland absorbs practically all of it. So it can help your doctor tell whether a lump in your neck is thyroid cancer.

Your doctor will give you a small dose of radioactive iodine, either in a shot or in a pill. A few hours later, a special camera scan shows where the radioactivity has gone. Parts of the thyroid that show less radioactivity than others might have cancer. Your doctor will use other tests to know for sure.

Radioactive iodine can also show whether cancer has spread beyond the thyroid. After you get the dose, the scanner checks your entire body for signs of radioactivity.

Thyroid Cancer

Radioactive iodine can kill the cells that make up the thyroid gland and thyroid cancer. If thyroid cancer has spread to other parts of the body, radioactive iodine can attack the disease there, too.

There’s another advantage to using it. When you take it in liquid form, the radiation won’t affect the rest of your body, because the thyroid cells soak up practically all of it.

After you get a dose of radioactive iodine from your medical team, your body will give off radiation for a while. So your doctor might keep you in an isolation room in the hospital a few days, so you won’t put others in danger. When it’s time to go home, your doctor may tell you to do certain things to keep others safe. Your side effects might include a sore neck, upset stomach, or dry mouth. You may find that food tastes different.

Radiation also may affect a man’s sperm count or a woman’s ovaries. Doctors often recommend that women wait 6 months to a year after the treatment before they get pregnant.

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If you have Graves’ disease, your thyroid makes too much hormone. Your eyes bulge or get red, or the area around your eyes swells. These symptoms tend to be more severe if you smoke. The skin on your shins can become thick and reddish, too, but this symptom is rare.

Radioactive iodine is the most common treatment for Graves’ disease. Other drugs or surgery may be options, and you and your doctor will choose based on how severe the illness is, among other things. If radioactive iodine is the treatment, you’ll probably swallow it in capsule form. The thyroid gland will absorb it and shrink. Then it will make less of the hormone.

If you get something called a “goiter,” it simply means that the thyroid is enlarged, sometimes because of Graves’ disease. If you have this condition, the treatment for Graves’ disease also will help make the goiter smaller.

If you’re a man with prostate cancer, radioactive iodine is one possible treatment. Your doctor may use it alone if your cancer is at an early stage or growing slowly. If there’s a greater risk that the disease will spread beyond the prostate, your doctor may pair it with radiation beamed into the body from outside.

The radioactive iodine treatment uses pellets of radioactive iodine about the size of a grain of rice, and it involves an operation. Your surgeon will put the pellets into the prostate, where they attack the disease by giving off radiation for weeks or months. The radiation may go beyond your body, so you might have to stay away from children and pregnant women for a while. Side effects can include diarrhea (watery bowel movements) and the need to pee often.

Eye Cancer

Radioactive iodine also treats a type of eye cancer called ocular melanoma or intraocular melanoma. This treatment calls for pellets inside a tiny disk. In the operating room, the medical team puts the disk next to your eye. It stays there several days, then the team removes it.

The operation to insert the disk lasts about 2 hours. Taking it out usually needs less than an hour. It may take 3 to 6 months for the radiation to have its full effect on the cancer.

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Cervical and Uterine Cancer

If you’re a woman with cervical or uterine cancer, radioactive iodine may be a treatment option. The medical team will put a device holding the iodine into your uterus or next to your cervix, or possibly in both places. It will probably have to stay there for 2 or 3 days. You’ll be radioactive while it’s there, so you’ll need to stay in a hospital room during that time. Family and friends will have to limit their visits, and doctors and nurses must avoid spending much time there.

To keep the device with the iodine from getting pushed out of place, you’ll have to stay in bed. Your pee will travel through a catheter, a small, flexible tube that’s inserted in your urethra and up into your bladder. Side effects may include discomfort in the pelvic area, constipation (trouble pooping), and a burning sensation when you pee.

WebMD Medical Reference Reviewed by Neha Pathak, MD on February 22, 2017

Sources

SOURCES:

American Cancer Society: “Radioactive Iodine (Radioiodine) Therapy for Thyroid Cancer,” “Radiation Therapy for Eye Cancer.”

American Thyroid Association: “Graves’ Disease.”

Eatright.org (Academy of Nutrition and Dietetics): “Iodine, a Critically Important Nutrient”

The Law Dictionary: “What is Radioactive?”

NCI Dictionary of Cancer Terms: “Radioactive iodine.”

Ocular Melanoma Foundation: “Treatment of Primary Tumors.”

OncoLink.org (Penn Medicine, University of Pennsylvania): “Internal Radiation Therapy (Brachytherapy).”

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