Answer to Question #8917 Submitted to "Ask the Experts"

Category: Nuclear Medicine Patient Issues — Diagnostic Nuclear Medicine

The following question was answered by an expert in the appropriate field:


I have hyperthyroidism and am going to get a dose of radioactive iodine. I was wondering why it is safe to be around my pets. Can I make my cats hypothyroid by petting them? I have three cats and I am very worried. They are crying to be around me.


It is safe to be around your cats after you are treated with radioiodine therapy because even if they are in your lap, the exposure is low. People do sweat out the radioiodine, but if you wash your hands regularly, that is very effective in washing away the small amount of contamination on your hands.

Even if you pet your cats and they lick their fur and ingest it, that is not a concern either.

Radioiodine is used to treat hyperthyroidism and thyroid cancer in cats. The amount of radioiodine on your palms is very low microcurie quantities. The amount of radioiodine that they give to cats to treat hyperthyroidism is typically 74 to 222 megabecquerels. And the majority of the cats that are treated to these large quantities (to a cat) return to a normal thyroid function. That means that their thyroids still produce thyroxine and they do not have to be supplemented with thyroid pills to have a normal metabolism. So there is no scenario that I can think of in which you could affect your cats after your treatment.

Marcia Hartman, MS

Answer posted on 19 March 2010. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.