Skip to Main Content
Ask About Financing

What is the best diet for a cat with hyperthyroidism?

Hyperthyroidism in cats occurs when their thyroid gland releases too much hormone, leading to severe health problems. Our veterinarians in Exeter provide a detailed explanation of this condition and how it can be managed through a modified diet.

What is hyperthyroidism in cats?

The thyroid glands are situated in your cat's neck and are responsible for producing a variety of hormones that regulate numerous processes in the body, controlling your cat's metabolic rate. In case the thyroid gland produces either too much or too little of these hormones, your cat may display symptoms of hypothyroidism (low levels of hormone) or hyperthyroidism (too much hormone).

If your cat is diagnosed with hyperthyroidism, their metabolism will speed up, resulting in an accelerated energy burn rate. This means that your cat might lose weight even if they are consuming more food than usual.

What are the symptoms of hyperthyroidism in cats?

Although any cat breed can be affected by hyperthyroidism, it is most commonly diagnosed in older cats, typically between 12 and 13 years old. Both male and female cats are equally susceptible to this condition. The symptoms of hyperthyroidism can be subtle at first and tend to worsen gradually over time. It is important to note that other health issues can also complicate or mask symptoms of hyperthyroidism. Therefore, it is recommended to seek veterinary care early if your cat shows any of the symptoms listed below.

Symptoms of hyperthyroidism in cats producing an excess of thyroid hormone may include one or more of the following:

  • Increase in thirst
  • Irritability
  • Restlessness
  • Mild diarrhea and vomiting
  • Increase in heart rate
  • Poor grooming habits
  • Excessive or increased appetite
  • Low heat tolerance 

As the condition of hyperthyroidism progresses in cats, they may exhibit unusual behavior such as panting when they feel stressed. While most cats with hyperthyroidism have a good appetite and seem restless, some may feel weak, lethargic or lose their appetite.

What causes hyperthyroidism?

For most cats hyperthyroidism is caused by a non-cancerous tumour located somewhere on the thyroid gland. In some rare cases however, the tumour can develop into thyroid cancer.

What are the long-term complications of hyperthyroidism?

If left untreated, hyperthyroidism in cats can have serious consequences, affecting the function of their heart and potentially leading to heart failure. Additionally, hyperthyroidism may cause high blood pressure in cats, which can lead to serious health concerns such as damage to the brain, kidneys, heart, and eyes.

If your cat is diagnosed with both hypertension and hyperthyroidism, medication will be necessary to control their blood pressure. It's worth noting that hyperthyroidism and kidney disease often occur simultaneously in older cats, which requires close monitoring and management, as treating hyperthyroidism can sometimes have negative effects on kidney function.

How is hyperthyroidism diagnosed?

Diagnosing hyperthyroidism in older cats can be a difficult task. Your veterinarian will conduct a physical examination and observe your cat's neck area for signs of an enlarged thyroid gland. At Pacific Crest Companion Animal Veterinary Hospital, our veterinary internal medicine team uses advanced diagnostic testing to help diagnose your pet's condition and provide appropriate care.

Because several conditions share the clinical symptoms of hyperthyroidism, your veterinarian may use different tests to diagnose your cat's condition. A complete blood count (CBC), urinalysis, and chemistry panel can assist in ruling out kidney failure and diabetes. A simple blood test that shows elevated T4 levels in the bloodstream may be enough for a definitive diagnosis. Your veterinarian may also check your cat's blood pressure or perform an electrocardiogram, chest x-ray, or ultrasound.

How will my vet treat my cat’s hyperthyroidism?

Depending on the results of your cat's tests, your vet may choose one of several treatment options for your cat’s hyperthyroidism.  They may include:

  • Radioactive iodine therapy (likely the safest and most effective treatment option)
  • Antithyroid medication
  • Surgery to remove the thyroid
  • Modified diet

How can hyperthyroidism be treated with a modified diet?

Hyperthyroidism is a common condition in cats that can be managed through an iodine-restricted prescription diet, which your veterinarian can prescribe. Iodine plays an essential role in the production of thyroid hormones. The goal of an iodine-restricted therapeutic diet is to reduce the production of thyroid hormones by limiting iodine intake in your cat's diet.

To ensure the effectiveness of this treatment, strict adherence to the low-iodine diet is necessary. However, this can prove to be challenging for pet parents and their cats. Apart from feeding your cat a prescription food, you will also need to strictly monitor your cat's treats and prevent your cat from hunting for their own meal while outside.

Several studies have shown that after three weeks of following a prescription hyperthyroidism diet, levels of thyroid hormones begin to decrease, and within a few months, they may even return to normal levels.

What is the prognosis for cats with hyperthyroidism?

Hyperthyroidism is a condition that commonly affects cats. If the condition is diagnosed and treated early, the prognosis is generally good. However, in some cases where the condition has become more advanced, complications with other organs can worsen the prognosis. Regular monitoring and follow-up appointments with the veterinarian are essential for managing the condition effectively.

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.

Do you think your cat has hyperthyroidism? Contact our vets in Exeter to schedule a consultation and get a diagnosis.

New Patients Welcome

Pacific Crest Companion Animal is accepting new patients! Our experienced vets are passionate about the health of Exeter companion animals. Get in touch today to book your pet's first appointment.

Contact Us

(559) 592-4753 Contact