Treating Hyperthyroidism in Cats

Hyperthyroidism is a common health issue in Edgewater for middle-aged and senior cats, but what exactly is hyperthyroidism in cats? What are the symptoms of hyperthyroidism in cats, and how can it be treated? Our veterinarians explain...

Thyroid Hormones & Your Cat's Health

Hyperthyroidism in cats is caused by overactive thyroid glands. It is a very common disorder characterized by an increase in thyroid hormone production, which causes a variety of unhealthy symptoms in your cat.

Thyroid hormones are used to regulate many processes in the body and to control the metabolic rate, and when too much of the hormone is produced, clinical symptoms can be quite dramatic and make cats severely sick.

Cats suffering from hyperthyroidism tend to burn energy too quickly, which results in weight loss despite eating more food and experiencing an increase in appetite. We’ll discuss more symptoms below.

What are the symptoms of hyperthyroidism in cats?

Hyperthyroidism is most often seen in older cats between 10 - 13 years of age. There does not appear to be any difference in the number of male cats diagnosed with hyperthyroidism vs the number of female cats with the disease.

Hallmark signs of hyperthyroidism that cat parents should watch for include:

  • Increase in thirst
  • Increased irritability or restlessness
  • Increase in heart rate
  • Poor grooming habits
  • Typically a healthy or increased appetite

Some cats will also have mild to moderate diarrhea and/or vomiting, while others will seek cooler places to lounge and have a low tolerance for heat.

Some cats may pant when stressed in advanced cases (an unusual behavior for kitties). While most cats have a healthy appetite and are active, some may be weaker, lethargic, or have a lack of appetite. The key is to notice any significant changes in your cat and have them addressed as soon as possible.

These symptoms are usually subtle to start and gradually become more severe as the underlying disease gets worse. Other diseases can also complicate and mask these symptoms, so it’s important to see your vet early.

What causes hyperthyroidism in cats?

For most kitties, benign (non-cancerous) changes in their bodies can trigger the condition. Both thyroid glands are most often involved and become enlarged (the clinical change is nodular hyperplasia, and it resembles a benign tumor).

Though we don't know what causes the change, it is similar to hyperthyroidism in humans (clinically named toxic nodular goiter). This disease is occasionally caused by a cancerous (malignant) tumor called thyroid adenocarcinoma.

What are the long-term complications of hyperthyroidism?

Hyperthyroidism can impact the function of the heart if left untreated, changing the organ’s muscular wall and increasing heart rate, often resulting in heart failure.

High blood pressure (hypertension) is also commonly seen in cats suffering from hyperthyroidism. Though we see this less often, it can result in damage to several organs including the brain, kidneys, heart, and even the eyes. If your vet diagnoses your cat with hypertension in addition to hyperthyroidism, medication will be required to control blood pressure.

Because hyperthyroidism and kidney disease are both common in older cats, they frequently coexist. When both of these conditions coexist, they must be closely monitored and managed, as treating hyperthyroidism can sometimes impair kidney function.

How is hyperthyroidism diagnosed?

Diagnosis of hyperthyroidism in senior cats can be difficult. Your veterinarian will perform a physical exam on your cat and palpate the neck area to look for an enlarged thyroid gland. Many other common diseases experienced by senior cats (intestinal cancer, chronic kidney failure, diabetes, inflammatory bowel disease, and others) share clinical symptoms with hyperthyroidism, so a battery of tests may be required to diagnose it.

A complete blood count (CBC) urinalysis and chemistry panel can help rule out kidney failure and diabetes.

A simple blood test showing elevated T4 levels in the bloodstream may be enough for a definitive diagnosis, though this is not true for 100% of cats due to concurrent illnesses or mild cases of hyperthyroidism, which can result in fluctuating levels of T4 or showing elevated T4 levels if another illness is influencing the result.

If possible, your vet may also check your cat’s blood pressure and perform an electrocardiogram, chest x-ray, or ultrasound.

What are the treatment options for cats with hyperthyroidism?

There are several methods for treating this condition in cats. Your veterinarian will recommend the best treatment for your cat based on your pet's specific circumstances as well as the benefits and drawbacks of each option. Your cat's hyperthyroidism treatment may include:

  • Radioactive iodine therapy (likely the safest and most effective treatment option)
  • Antithyroid medication, administered orally, to control the disease for either the short-term or long-term
  • Surgery to remove the thyroid gland
  • Dietary therapy

What is the prognosis for cats with hyperthyroidism?

Your kitty’s prognosis for hyperthyroidism will generally be good with appropriate therapy, administered early. In some cases, complications with other organs can worsen the prognosis.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Is your cat exhibiting signs of hyperthyroidism? Contact us today to book an examination for your feline friend.