Radioiodine Therapy

What is Radioiodine Therapy?

Iodine is an element required for normal health. In the body it is used primarily by the thyroid gland (located in the neck) to produce thyroid hormones. These hormones play a large role in your pet’s metabolism and can cause major problems when they are not produced at normal levels. Radioiodine (I-131) is a form of iodine that has been made radioactive. In its radioactive state, it undergoes a natural process (decay) during which it gives off radiation. The radiation omitted consists of two types; beta and gamma. The half-life of I-131 is eight days; in other words, one-half of the radioiodine goes through this decay process every eight days.

When taken into the body, a large percentage of radioiodine accumulates in the thyroid gland. The remainder of the I-131 is excreted in the urine and feces. Once the radioiodine is taken up by the thyroid gland (or thyroid tumor in a hyperthyroid cat), the gamma rays and beta particles are released. The beta particles travel a maximum of 2-5 mm in tissue. Therefore, beta-particles are locally destructive but spare adjacent normal thyroid tissue, parathyroid glands and other cervical structures. The radiation selectively destroys the thyroid tumor cells and thus treats the hyperthyroid condition.

The radioiodine is given as a single dose on the first day of hospitalization. After the treatment is administered, the patient is placed in isolation. The patient is monitored at the hospital for a few days until its radioactivity level is low enough to permit release from the hospital, which is determined by state and federal regulation. By law, visitation is not permitted. During their stay, the cats are monitored by a licensed full time veterinary team. If you wish, you may call us to check on the status of your cat. It is routine for us to call each owner with daily progress reports.


Please talk to your Veterinarian and discuss the options for your pet.  Keeping their weight down can add more time to your life together and more life to the time you spend with your furry best friend!