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A Cure for Feline Hyperthyroidism

Feb 21, 2020

It’s National Cat Month!

Here’s to the love we share with our purry pals every day.

As those kitten days become years, many older cats develop hyperthyroidism.  Hyperthyroidism is a condition that affects middle-aged to older cats and is caused by a benign tumor of the thyroid gland.  The condition can occur in any breed of cat, male or female but occurs almost exclusively in older cats; average age is between 12 to 13 years old.  The tumor causes the overproduction of the thyroid glands and can lead to many health issues which can be fatal.  Luckily, feline hyperthyroidism is treatable!

Symptoms of hyperthyroidism:

  • Increased appetite
  • Weight loss
  • Vomiting
  • Diarrhea
  • Hyperactivity
  • Increased heart rate
  • Heart murmurs
  • High blood pressure

It is important to consult your veterinarian if your cat starts experiencing any of these symptoms.  Excessive thyroid hormone affects every organ which left untreated, could lead to heart conditions and high blood pressure. To diagnose feline hyperthyroidism, a simple blood test known as a “T4” is performed to test the cat’s thyroid hormone level.

Thanks to our advanced medical options and treatments, this story usually ends well!

Treatment for hyperthyroidism:

Many of our Compassion-First Pet Hospitals offer a variety of treatment options to help treat hyperthyroidism one of which permanently cures the condition.

The treatment is called radioactive iodine, or I-131 therapy. Radioiodine therapy is performed by an injection of radioactive iodine and is given under the cat’s skin.  The simple, non-invasive treatment destroys the abnormal thyroid cells without damaging surrounding tissues, permanently correcting hyperthyroidism.  Over 95% of cats are cured on their first injection making radioiodine therapy the treatment of choice as it is cost-effective and cures the condition.  A very small percent (<5%) of cats requires a second injection of a higher dose of radioactive iodine to fully treat their condition.

The dose of radioactive iodine is very low making the human radiation exposure risk also very low.  To be cautious, treated cats are hospitalized typically two to five days after their injection in a special area of the pet hospital until their radioactivity reaches an acceptable level.  During this stay, pet owners are not able to visit their cats.

Benefits of radioactive iodine therapy:

  • 95% curative
  • No surgical risk
  • No long-term medication or ointment application required
  • Least-expensive long-term treatment
  • Does not require anesthesia
  • No serious side effects


Most pet parents can expect their feline friends to be back home knocking things off the coffee table in no time.

Post-treatment, there are a few precautions pet owners should take, such as:

  • Avoid contact with contaminated objects – Before your cat returns home, make sure all of their bedding, toys, and other contaminated items are either sanitized or bagged and stored for 3 months.
  • Limited interaction – You should have limited interaction with your cat the first two weeks after they return home from their I-131 treatment. To be cautious, we recommend that people under 18 or pregnant women should not have any direct contact with your cat during this time.  You should keep your purry friend confined inside and you should not hold or allow your cat to sit or sleep with you.  We understand that this will be a long and difficult two weeks not being able to love on your cat, but limited interaction will decrease your exposure to the radiation.
  • Proper waste disposal – Radiation will exist in your cat’s urine and feces for up to three months after their treatment, so it is important to dispose of their liter daily by flushing it down the toilet and into the sewer system.

Post I-131 treatment, blood tests will be performed on your cat’s thyroid hormone levels at one, three and six months. The blood tests will monitor the effectiveness of the treatment to ensure the injection was successful.

Learn more about this effective treatment by checking out our Compassion-First Pet Hospitals that provide radioactive iodine therapy.


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