Answer to Question #13658 Submitted to "Ask the Experts"

I had iodine radiation therapy post total thyroidectomy. What are the long-term effects in months that the radiation can cause in the gastrointestinal system including the salivary glands? Are they permanent or temporary? How long does the radiation stay in the body or items such as dental retainers?

My first recommendation is that if you are experiencing chronic dry mouth or pain and swelling in your cheeks or under your jaws, you should contact the nuclear medicine physician who treated you with the radioiodine. These symptoms are likely to be related to your ¹³¹I therapy, and treatments for them may be available.

Inflammation of the salivary glands (sialadenitis) is a common complication of high-dose ¹³¹I therapy for thyroid cancer. Some patients report mild pain and swelling in the cheeks and neck within the first week or so following ¹³¹I treatment, which are relieved by over-the-counter anti-inflammatory drugs such as ibuprofen and go away on their own. For other patients, a dry mouth and chronic discomfort around the salivary glands may last for months or even years. The chances of experiencing chronic symptoms depend upon your age, whether you are a post-menopausal woman, and whether you have any other underlying immune system problems. In addition, the likelihood of chronic salivary gland problems increases with increasing dosages of ¹³¹I.

Other than sialadenitis, the most common gastrointestinal symptoms following ¹³¹I treatment are nausea and vomiting. Diarrhea is less common. All of these symptoms occur within a few days of ¹³¹I treatment, may be managed with medication, and go away on their own.

Since you had your thyroid gland removed before your ¹³¹I treatment, most of the residual radioactive iodine is removed from your body quickly by your kidneys. Within a week or two, less than 1% of the ¹³¹I will remain in the body for most patients, and that small remainder will continue to disappear through radioactive decay. Small amounts of ¹³¹I will continue to be secreted from your salivary glands for a few months and may stick onto your dental retainer. Simple cleaning of the retainer will remove the ¹³¹I. Contamination of the retainer is not a hazard to you or people in your household.

To sum it up, most patients experience some sort of gastrointestinal symptoms, which are usually limited to short-term nausea, vomiting, diarrhea, and salivary gland pain and swelling. If the nausea, vomiting, and diarrhea persist, they may be due to a medical issue that is not related to your ¹³¹I therapy, and you should have them checked out by your doctor. Chronic dry mouth and salivary gland pain are known long-term complications of high-dose ¹³¹I therapy, and treatments are available for them. If you are experiencing them, please contact your nuclear medicine physician.

I hope this response helps.

Robert E. Reiman, MSPH, MD