Hyperthyroidism in Senior Cats

  • Is your cat losing weight despite a good appetite?
  • Is your usually lazy cat suddenly more active? Restless, more vocal and waking you up at 3 am for a midnight snack?
  • Do you find yourself filling up the water bowl more often, and emptying out the litter box a lot more?
  • Has your senior cat developed more digestive issues, vomiting and having diarrhea on and off?

If you answered “YES” to any of these questions your cat may be hyperthyroid. Hyperthyroidism is a condition caused by a usually benign growth in the thyroid gland of the cat. It is usually seen in senior cats 9 years old and up.

The growth causes an overproduction of thyroid hormone, resulting in the cat’s metabolism being “sped up”. This causes weight loss despite a good appetite, a racing heart, and an upset digestive system due to overeating. Untreated, it can lead to heart failure from an overworked heart, can cause weakness and emaciation and greatly impact your cats quality of life. A simple blood test can check to see if your cat is hyperthyroid.

Treatment for hyperthyroidism usually starts with a medication. Called methimazole, which works by inhibiting the production of the thyroid hormone. This doesn’t necessarily mean that you will have to chase your cat around the house with a pill. It is possible now to have the medication made into transdermal and liquid forms, so much easier to give. Periodic blood tests are necessary to ensure the correct dosage is being given.

Another option for treatment is a commercial food called y/d which is iodine restricted. Iodine is important for the synthesis of the thyroid hormone, and without it, the hormone levels return to normal. The drawback with this food is that the cat can not eat any other types of food, no treats or other snacks.

The gold standard for treating hyperthyroidism is radioactive iodine. An injection is given which renders the thyroid gland inactive. This occurs only in specific treatment facilities and the cat is usually boarded for a week so to avoid contact with other pets and people while temporarily “radioactive”. In most cases after this treatment no further medications are needed.

Hyperthyroidism- it’s worth testing your senior cat for. Please speak to your Veterinarian at Eastern Shore for more information.

Written by: Dr. Celeste Forgeron DVM