Hyperthyroidism in Elderly Cats

Getting old is no picnic. Grumpy knows.
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As Kitty ages, he's likely to face some health challenges. Hyperthyroidism, or overactive thyroid, is one of the most common diseases facing elderly felines. As an attentive cat owner, you'll notice changes in your cat that might indicate the disease. Get Kitty looked at as soon as possible.


Your cat's thyroid glands regulate almost every area of his metabolism, including his heart, kidneys and blood pressure, so symptoms of a thyroid in overdrive affect many parts of his body. According to Washington State University's College of Veterinary Medicine, cats are diagnosed with hyperthyroidism at the average age of 13, with fewer than 5 percent diagnosed before the age of 10. That truly makes it an elderly cat disease.

Thyroid Glands

Kitty has two thyroid glands in his neck that produce hormones called T3 and T4. Either or both glands can start producing too much thyroid hormone; it's more common for both to be involved. Kitty might suffer from an adenoma on his thyroid glands, a noncancerous tumor. While malignant thyroid tumors also occur, they are rare.


If your old cat loses weight even though he eats more like a horse than a feline, his thyroid might be out of whack. He might start drinking and peeing a lot more. He might stop grooming himself regularly, making his coat look unkempt or matted. Kitty might have bouts of vomiting and diarrhea.

Those are all symptoms you can notice. What's not visible, though, is even more important. Kitty might develop high blood pressure, or hypertension, from his hyperthyroidism. Hypertension poses a risk to his kidneys; extremely high pressure can cause blindness. The disease also affects his heart, causing a thickening and enlargement, along with congestive heart failure.


Your vet diagnoses Kitty's hyperthyroidism through a physical examination and blood work that tests the level of thyroid hormone in his body. She feels for enlarged thyroid glands in Kitty's neck. Along with ordering blood work for thyroid hormone, your vet will test your cat's urine and blood for kidney and liver function, as older cats often have diseases in these organs.


There are several ways to treat old cats with hyperthyroidism, so you and your vet can discuss what's best for your particular kitty's situation. Your choices may be limited if Kitty isn't in good overall health. Twice-daily medication might help keep Kitty's symptoms under control, along with routine blood testing to make sure the medication is working. Surgical removal of the thyroid glands cures many cats, although there's always a risk when anesthetizing an older cat.

Larger veterinary hospitals might offer radioactive iodine therapy, in which a cat is injected with the substance. Only certain facilities are licensed to handle radioactive material. Kitty must stay at the veterinary hospital for two weeks or longer until the amount of radioactive material in his body falls to a level where he won't potentially expose someone. You probably can't visit him during this period. According to the Cornell University College of Veterinary Medicine, radioactive iodine therapy cures 95 percent of cats with hyperthyroidism.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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