Radioactive Iodine Therapy

Radioactive Iodine Therapy

Radioactive iodine (I-131) therapy (also called radioiodine therapy) is commonly used to treat papillary and follicular thyroid cancer, the most common forms of thyroid cancer. Many, but not all thyroid cancer patients receive radioiodine. Some smaller thyroid cancers may not require iodine treatment. Also, because anaplastic and medullary thyroid cancers do not take up iodine, they cannot be treated with radioactive iodine. Treatment ordinarily starts about eight weeks after surgery and is given at UWMC. Patients are typically given doses of radioactive iodine that require a hospital stay of two to three days. Your doctor will explain any precautions you may need to take to avoid exposing other people to any radiation during your treatment.

Before beginning radioactive iodine treatment, doctors may perform a thyroid scan using a small dose of the radioactive isotope I-131. The scan will show whether any normal thyroid tissue remains after surgery as well as thyroid cancer cells that may have spread.

Radioactive iodine treatment works best when your levels of thyroid-stimulating hormone (TSH) are high. For this reason, your doctor will have you either discontinue synthetic thyroid hormones or take a synthetic TSH-elevating hormone, thyrogen, for two days before administering the treatment.

High-dose radioactive iodine comes in a capsule that you swallow. I-131 travels through the bloodstream and collects in thyroid cancer cells, killing them. The radiation clears from the body in about a week, with only traces showing up after three weeks. Drinking plenty of fluids during the treatment period helps to protect your bladder and to rid the body of the I-131. Laxative treatments also help to reduce the exposure of the colon to radiation at the time of treatment. 

Side Effects

You may experience some of the following side effects from treatment with radioactive iodine:

  • nausea
  • stomach pain
  • pain and swelling of the salivary glands (felt in the neck)
  • dry mouth
  • dry eyes
  • loss of sense of taste or smell

Most often these effects last only a few days. Salivary gland effects (dry mouth and loss of taste) often last two to three, or several, weeks, but usually resolve. However, radioactive iodine treatment can occasionally cause long-term effects to the salivary glands and sometimes the lacrimal (tear) glands.

Approximately eight hours from the time you receive your radioiodine therapy dose, your doctor may ask you to suck on lemon candy to encourage your salivary glands to secrete radioiodine they have absorbed; this will help to minimize salivary gland discomfort and radiation side effects.

If you have ongoing trouble with any side effects of treatment, your doctor can provide you with ways to relieve your discomfort.