Hyperthyroidism in Cats

Cats have two glands on either side of their trachea (windpipe) called the thyroid glands. These glands help control metabolism and other important processes throughout their bodies.

Hyperthyroidism occurs when these glands enlarge and start producing an excess amount of thyroid hormones, throwing off the normal functions of the body. Hyperthyroidism is one of the most common diseases we see in the veterinary industry. In almost all cases, hyperthyroidism is seen in senior cats over ten years of age. We recommend bi-annual wellness exams in senior patients to monitor for diseases like hyperthyroidism to catch them in the early stages. It is especially important for hyperthyroid cats as the disease can start to affect other organs in the body such as the kidneys and heart if left untreated.

Common Symptoms

  1. Increased appetite with weight loss: this is one of the most common clinical signs we see in hyperthyroid cats.
  2. Cats can become very vocal and cry for food constantly even though they’ve just eaten. They often eat ravenously but cannot put on weight
  3. Increased drinking and urination
  4. Restlessness and vocalization: vocalizing excessively for food, seeming very “hypersensitive” to surroundings
    Greasy, messy fur: unkempt, matted or greasy coat

If your cat is experiencing any of these symptoms, please take them to see your veterinarian. Although common in hyperthyroid cats, these symptoms can indicate other disease processes as well.

Your veterinarian may want to proceed with some diagnostic tests to determine the cause of these symptoms. Often blood work will be performed to check organ function and thyroid hormone levels in the blood. If your cat is also experiencing trouble in the litter box, your veterinarian may recommend a urinalysis to rule out a urinary infection and to check kidney function. Veterinarians will check your cat’s heart rate and may also check blood pressures as these values are often elevated in hyperthyroid cats.

There are a few options for treating hyperthyroidism, each with their pros and cons. Your veterinarian can discuss with you what the best choice would be for your cat.

  1. Medication: It is the most common treatment option. These medications are usually given twice daily to inhibit excess thyroid hormone production. The medication can come in tablet or liquid form (liquid comes in different flavours). There is also a transdermal gel option that can be rubbed on the inside of your cat’s ear flap if they are more difficult to medicate. Bloodwork will need to be periodically performed to monitor thyroid hormone levels.
  2. Radioactive iodine: Performed at specialty clinics with proper radiation protocols, a small amount of radioactive iodine is injected that destroys overactive tissues. This treatment is the most expensive but can be curative in most cases.
  3. Surgery: Although not a common treatment, in some cases, the thyroid glands can be surgically removed. There can be complications with surgery and recurrence of the disease.
  4. Food: If other options have been exhausted, some cats have had success with being fed a prescription diet that is low in iodine. It is a tricky option as it must be the only food fed (no treats, or table scraps) and relapse will occur if the cat becomes uninterested in the food. Always talk to your veterinarian before switching diets.

Although this sounds like a lot of scary information, hyperthyroidism is a treatable disease and kitties can live many happy years after their diagnosis. My cat, Peach, was diagnosed with hyperthyroidism almost a year ago and has been happily taking her thyroid medication twice daily in a pill pocket treat!

Written by: Amy Lee, RVT

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