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The essentials

  • Hyperthyroidism is a common disease of the endocrine system in cats — It’s most often seen in middle-aged kitties over the age of 8.
  • Thyroid hormones affect almost every organ in the body — As a result, cats with hyperthyroidism may exhibit a wide array of symptoms.
  • There are several treatment options for hyperthyroidism in cats — These include diet changes, medication, iodine therapy, and in some cases, surgery.

What is hyperthyroidism in cats?

In cats, hyperthyroidism is a hormonal disorder marked by elevated thyroid hormones. In many cases, the disease is caused by benign tumors that enlarge the thyroid gland, though the cause of these tumors is largely unknown. While the condition can occur at any age, it’s most commonly seen in middle-aged or senior cats over the age of 8.

Hyperthyroidism accelerates a cat’s metabolism, which can negatively affect nearly every organ in a cat’s body. Since the condition often leads to complications such as heart failure, kidney disease, and high blood pressure, early detection is key to a cat’s recovery. Familiarizing yourself with some of the most common clinical signs of hyperthyroidism in kitties can help you seek out treatment for your pet as soon as possible.

Common signs and symptoms

Like other common endocrine disorders, hyperthyroidism can cause a variety of symptoms in cats. Many of these signs reflect an increase in your cat’s metabolism and heart rate. Since cats don’t often openly display pain, it’s up to pet parents to monitor any changes in their pet’s behavior. Some of the most common symptoms of hyperthyroidism include:

Treating your cat’s hyperthyroidism 

If you suspect your cat has hyperthyroidism, your first step should be to visit a veterinarian right away. A vet will usually perform a physical exam and feel your cat’s neck for an enlarged thyroid gland. Your pet’s vet will also take your cat’s medical history into consideration and look for clinical signs of the condition.

In order to confirm the diagnosis, a vet will usually conduct blood tests and a urinalysis. They may also perform a chest X-ray.

Thankfully, there are several treatment options. You’ll need to talk with your vet to determine what might be best for you and your cat. Currently, the four widely accepted courses of treatment for kitties are as follows:

Radioactive iodine therapy. This approach is the preferred treatment in many cases. Radioactive iodine, also called radioiodine, is administered to a cat via injection. The therapy has proven to be extremely effective, curing 95% of cats with hyperthyroidism.

Surgical removal of the thyroid gland. While it may seem extreme, surgery is generally considered a safe and effective treatment method. Thyroidectomy, or removal of the thyroid glands, does require your cat to be under anesthesia. A vet may choose to remove half or all of the gland, depending on the size and location of the tumor. In some cases, your cat may need further treatment with synthetic thyroid hormones.

Antithyroid medication. Antithyroid drugs like methimazole work to reduce the overproduction of thyroid hormones. In most cases, these drugs are administered orally, but topical skin gels have also proven effective. Cats most commonly receive a long-term, twice-daily dosage of an antithyroid. However, these medications can cause side effects like fever and lethargy in some cats.

Dietary therapy. For cats with mild symptoms, an iodine-restricted diet is an option. However, there isn’t a lot of information about the long-term effects of this diet on a cat’s overall health. If you do opt for dietary therapy to treat your cat’s hyperthyroidism, make sure to work with your vet to formulate an appropriate nutrition plan. These diets aren’t recommended for multi-cat households, as healthy cats should not ingest these foods.

Caring for your cat’s kidneys and heart

Since the thyroid gland plays such a vital role in so many bodily functions, hyperthyroidism can easily lead to complications. Often, these secondary problems are seen in a cat’s organs, like the heart and kidneys. Elevated thyroid hormones can also alter a cat’s metabolism, which can cause their heart rate to increase and the heart muscles to thicken. If left untreated, this can lead to heart failure. The thyroid plays a role in kidney function and blood flow, both of which can be adversely affected by elevated hormone levels.

For now, there’s no way to prevent hyperthyroidism. But, there are some steps you can take to keep a close eye on your pet’s health. Most important of these is to regularly take your cat in for checkups. Clinical signs of disease can be hard to recognize in kitties, so your best bet is to leave your pet’s diagnosis to professionals.

Frequently asked questions

How common is hyperthyroidism in cats?

Hyperthyroidism is most common in middle-aged and senior cats and affects about 1 in 10 cats over the age of 10.

What are the symptoms of hyperthyroidism in cats?

Many clinical signs reflect an increased metabolic rate. Weight loss, heart murmurs, and an increase in appetite, thirst, and urination are the most common symptoms.

What complications can hyperthyroidism cause?

Possible complications of hyperthyroidism include high blood pressure, kidney disease, and heart failure. Treatment helps to reduce the risk of these and other secondary conditions.

How is hyperthyroidism treated in cats?

Common treatments include radioactive iodine therapy, surgery, medication, and dietary therapy. Always consult your vet to determine which treatment option is best for your cat.

How long can a cat with hyperthyroidism live?

The prognosis for cats given proper treatment methods is usually good. With effective management of the disease, cats with hyperthyroidism can live for many years.