Identifying Feline Hyperthyroidism

Our Feline friends are generally healthy and well fed in their indoor living environment. However, there are a few internal diseases that are common among middle aged and older cats.

What is Feline Hyperthyroidism? It’s basically an overproduction of thyroid hormone from a tumor in the thyroid gland. The enlargement is benign in the vast majority of cats (98%) – known as a thyroid adenoma. Though the remaining 2% develop thyroid cancer as a result. The elevated thyroid hormone increases the cat’s metabolism causing their internal organs (heart, liver and kidneys) to work overtime.
Feline Hyperthyroidism is a fairly common diagnosis in veterinary hospitals. The major clinical signs of a cat with Hyperthyroidism are as follows:

  • Weight loss
  • Ravenous appetite and thirst
  • Poor, unkempt hair/coat
  • Rapid heart rate
  • Vocalization
  • Nervousness
  • Occasional vomiting and diarrhea

Special attention should be focused on the very thin cat with a huge appetite. If your cat is excessively thin but consumes large quantities of food, make an appointment at your local veterinary clinic as soon as possible.
Your vet will perform a physical, including examining your cat’s thyroid gland, located in throat close to the Adam’s Apple. Diagnosis is then made by blood work to measure the thyroid levels and anything else that might be causing your cat’s symptoms. If available, a thyroid scintigraphy is performed too.
If blood work confirms your cat has Feline Hyperthyroidism, there are a number of fine treatment options available. Anti-thyroid medication comes in a tablet form known as Methimazole, which helps inhibit the production of the thyroid hormone. The pills are small and, although cats generally hate all oral medications, most cat owners should be able to administer the medication with a little training. Check out this video for advice on how to pill your cat.
Iodine is essential for thyroid hormone production in felines. So, another rather simple option is a prescription diet cat food that’s low in iodine. A popular one is Hill’s Prescription Diet y/d Feline which comes dry or canned. An iodine-restricted food like this inhibits thyroid hormone production and most cat owners are satisfied with the outcome. It also means they don’t have to struggle with oral medication.
Surgery is also an option with a procedure called a Thyroidectomy. This is a rather costly procedure that must be performed under general anesthesia. Side effects can occur however, including damage to the parathyroid gland which controls calcium metabolism.
Lastly, Radioiodine Therapy is a common, successful treatment – usually with good recovery. Basically a radioactive isotope (Radioiodine-131) is injected under the skin. This molecule destroys the cancer tissue in the thyroid yet does not affect the normal tissue. Cats need hospitalization for a number of days and there are strict go home procedures dealing with radioactivity.
Follow up care involves returning to the veterinary clinic for blood work to monitor the proper thyroid hormone levels and hopefully weight gains.

How Can Activ4Pets Help?

Activ4Pets is your cat’s personal health assistant and tracks their entire veterinary history. This includes test results, screening, surgeries, medications and more. So, if your cat is diagnosed with Feline Hyperthyroidism, Activ4Pets stores all the paperwork for you, so you always have the medical information at your fingertips to easily manage dosages and follow up. There’s no need to try and remember details, nor search through paper records any more.
Following treatment, you can also schedule a virtual follow up consult with your veterinarian, on the Activ4Pets platform. We all know cats loath car travel. So, a simple audio/video e-Consultation is a great benefit to cat owners.
February is designated Responsible Pet Owners Month. With Activ4Pets’s discounted membership starting at just $2 per month – it couldn’t be a better time to get started!

Meet the Author


Dr. Clayton Jones

Dr. Jones has 25 years of veterinary medical experience as a staff veterinarian and medical director of his own practice. As well as being the Chief Veterinary Medical Officer for Activ4Pets, Dr. Jones is also a member of the American Veterinary Medical Society and President of the US-Cuba Veterinary Cooperation Society.

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