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What is hyperthyroidism in cats?

Middle-aged and senior cats in Orlando are commonly diagnosed with hyperthyroidism, but what exactly is this condition? Our vets list symptoms and explain how hyperthyroidism in cats can be treated. 

Thyroid Hormones & Your Cat's Health

Overactive thyroid glands can cause hyperthyroidism in cats. This very common disorder is marked by an increase in production of thyroid hormones, which can result in your cat displaying numerous unhealthy symptoms. 

Thyroid hormones are used to regulate many processes in your feline friend's body. They also control the metabolic rate. When an excessive amount of the thyroid hormone is produced, clinical symptoms can make cats severely ill and show up quite dramatically. 

Cats suffering from this disorder tend to burn energy too quickly, which causes weight loss even as they eat more food and experience an increased appetite. Find more symptoms below. 

What are symptoms of hyperthyroidism in cats?

Older cats between 10 and 13 years of age are most likely to be diagnosed with hyperthyroidism. There does not appear to be any difference in the number of male cats vs. the number of female cats diagnosed with the disorder. 

Signs of hyperthyroidism cat parents should be on the lookout for include:

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

Some cats will also experience mild to moderate vomiting and/or diarrhea. Others will migrate to cooler places to lounge (such as a tile floor or bathtub) and have a low tolerance to heat. 

If your kitty has an advanced case of hyperthyroidism, they may pant when feeling stressed (an unusual behavior for cats). While most cats may eat well and exhibit restlessness, some may be lethargic, have a lack of appetite or feel weak. Remember to watch for significant changes in your cat's mood or habits, and have them addressed by a vet earlier rather than later. 

These symptoms will usually appear in subtle ways at first, then gradually become more severe as the underlying disease worsens. Other health conditions can also mask and exacerbate these symptoms, so it's important to have your cat examined by your vet early on.

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’re not sure what causes the change, it is much like hyperthyroidism in humans (clinically named toxic nodular goiter). Rarely, a cancerous (malignant) tumor called thyroid adenocarcinoma is the underlying cause of this disease.

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, and 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.

Hyperthyroidism and kidney disease often occur at the same time, as they are both commonly seen in older cats. When both these conditions are present, they need to be closely monitored and managed as managing hyperthyroidism may sometimes adversely affect kidney function.

How is hyperthyroidism diagnosed?

Diagnosing hyperthyroidism in senior cats can be challenging. Your vet will complete a physical exam and palpate your cat’s neck area to look for an enlarged thyroid gland. A battery of tests may be required to diagnose hyperthyroidism in your cat, as many other common internal diseases and conditions experienced by senior cats (intestinal cancer, chronic kidney failure, diabetes, inflammatory bowel disease and more) share clinical symptoms with hyperthyroidism. 

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.

How will my vet treat my cat’s hyperthyroidism?

There are a few different approaches when it comes to discovering the answers to how to treat hyperthyroidism in cats. Your vet will recommend the best treatment for your kitty based your pet’s specific circumstances and the advantages and disadvantages of each option. Your cat's treatment for hyperthyroidism 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 showing signs of hyperthyroidism? Contact our East Orlando Animal Hospital veterinarians today to schedule an examination for your four-legged friend.

Caring for Pets in Orlando

Caring for Pets in Orlando

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