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  • Has your cat been diagnosed with hyperthyroidism?
  • Has your cat been experiencing symptoms of weight loss, increased appetite, vomiting, or diarrhea?
  • Is your cat currently taking medication (methimazole) for hyperthyroidism?

I-131 (a.k.a. radioactive iodine) is considered the “gold standard” treatment for hyperthyroid cats. Other treatments include more expensive surgery and may still require long-term medication.

Until now, I-131 treatment has been too expensive for too many pet owners. Because we want to make this treatment accessible to more cats and their families, St. Francis Animal Hospital is now offering local and more affordable I-131 treatment.

What is I-131 Therapy?

I-131 therapy is a non-invasive treatment for feline hyperthyroidism using a radioactive isotope of iodine. This is the “Gold Standard” or very best treatment option. Thyroid cells require iodine to make thyroid hormones and thus iodine is concentrated in these cells. When radioiodine is given, it is concentrated in the hyperactive cells that are causing hyperthyroidism. The goal of therapy is to restore normal thyroid function.

What is feline hyperthyroidism?

Feline hyperthyroidism (HT) is the overproduction of hormones, predominately T4, by the thyroid glands. In most cases, this is due to a benign area of tissue in one or both glands that are overactive. Signs of hyperthyroidism are due to the increased metabolic rate caused by the high thyroid hormones and can include the following:

  • Increased appetite
  • Weight loss
  • Vomiting
  • Diarrhea
  • Hyperactivity
  • Increased thirst
  • Increased urination

How is feline hyperthyroidism diagnosed?

This can be handled by any veterinarian during an examination and by running bloodwork. In most cases, HT is diagnosed based on an increased total T4 concentration and compatible clinical signs.

What is the success rate with radioiodine therapy?

I-131 therapy is successful in resolving HT in 90-95% of cases with a single treatment.

A small percentage of cats may remain hyperthyroid after therapy. In those cases, repeating I-131 therapy may be recommended.

Rarely, lifelong thyroid supplementation will be required if too much thyroid function is eliminated during treatment.

How is I-131 therapy administered?

The radioiodine is injected under the skin, similar to a vaccination.

Where does my cat stay in the hospital after therapy?

After treatment, cats are housed in large cages in an isolated section of the hospital. A technician will monitor the cat daily and provide you with updates.  You will not be able to visit your cat during this brief time.

How do I schedule my cat for radioiodine therapy?

Either you or your regular veterinarian can schedule an appointment with us for an initial evaluation and consultation. During this visit, the doctor will review your cat’s medical history, perform a physical exam, and discuss whether I-131 therapy would be an appropriate treatment for your cat.