How does it work?
The treatment of choice for feline hyperthyroidism is radioiodine treatment. People also call this the I131 treatment. The hyperthyroid cat will receive an injection of a small dose of radioactive iodine. The injection is specifically dosed for the thyroid hormone level of your cat, minimizing the chances of overdose. Only the abnormal thyroid tissue takes up the radiation, leaving the normal thyroid tissue to function. Even though this radiation exposure has minimal risks to the owner and the cat, it still requires specially licensed facilities to administer the treatment, and special protocols must be followed after discharge from the clinic.
The advantages of radioiodine outweigh the disadvantages of needing to go to a special facility and a couple of weeks of a different routine at home. I131 therapy is curative in 99% of cats, there is no anesthesia or potential surgical complications, and no risk of drug reaction that is seen with methimazole. And no more daily medicating!
With accurate dosing, the overwhelming majority of cats will not need thyroid replacement medications. Very rarely after treatment, the thyroid levels will fall too low. This can be transient, but on very rare occasions, a cat with low thyroid levels will need to be supplemented.
 2016 AAFP Guidelines for the Management of Feline Hyperthyroidism. J Feline Med Surg. 2016 May;18(5):400-16.
If you have any questions or comments about how we can care for your cat, please contact us today at 443-207-2090.