What is the best diet for a cat with hyperthyroidism?

Your cat's thyroid releases hormones that help regulate many body processes. If thyroid hormone levels become too high (hyperthyroidism), your cat is at risk of developing many serious health issues. Today, our Novato vets share more about cat hyperthyroidism and how it can be treated with a hyperthyroid diet.

What is hyperthyroidism in cats?

The thyroid glands are located in your cat's neck and produce various hormones that regulate many processes in the body and control your cat's metabolic rate. If the thyroid produces too much or too little of these hormones, your cat will either show symptoms of hypothyroidism (low levels of hormone) or hyperthyroidism (excess hormone).

If your cat is suffering from hyperthyroidism, their metabolism will speed up. This means that your cat will tend to burn energy too quickly, resulting in weight loss, even if you notice that your kitty is eating considerably more food than usual.

What are the symptoms of hyperthyroidism in cats?

While any breed of cat can develop hyperthyroidism, most diagnosed cats are older, typically between 12 and 13 years old. Both female and male cats are equally affected. The symptoms of hyperthyroidism in cats are usually subtle at first and become more severe over time.

Other underlying health issues can also complicate or mask symptoms of hyperthyroidism. Therefore, you must consult your vet early if your cat has symptoms below. Cats with excessive thyroid hormone levels may exhibit one or more of the following symptoms:

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

When the condition becomes more advanced, some cats will pant when stressed, which is unusual. Although most cats suffering from hyperthyroidism have a good appetite and are restless, others may feel weak, lethargic, or lack appetite. 

What causes hyperthyroidism?

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

What are the long-term complications of hyperthyroidism?

Untreated hyperthyroidism can affect your cat's heart function and potentially lead to heart failure. Cats with hyperthyroidism may also develop high blood pressure, which can lead to serious health issues such as brain, kidney, heart, and eye damage. If your cat is diagnosed with hypertension alongside hyperthyroidism, they will need medication to control their blood pressure.

Hyperthyroidism and kidney disease often occur simultaneously in older cats when both conditions are present, close monitoring and management are necessary, as managing hyperthyroidism can sometimes have an impact on kidney function.

How is hyperthyroidism diagnosed?

Diagnosing hyperthyroidism in older cats can be a bit challenging. Your vet will perform a physical exam and check your cat’s neck area for signs of an enlarged thyroid gland. Our veterinary internal medicine team uses diagnostic testing to help identify your pet's condition and offer advanced care.

Since there are various conditions with similar symptoms to hyperthyroidism, a range of tests may be used to diagnose your cat's condition. 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 sufficient for a definitive diagnosis. Your vet 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 special food?

Hyperthyroidism in cats can often be managed through an iodine-restricted prescription diet from your vet. Iodine intake is necessary for the production of thyroid hormones. The goal of an iodine-restricted therapeutic diet is to help reduce the production of thyroid hormones by lowering iodine in your cat's diet.

Adhering strictly to the low-iodine diet is necessary for this treatment to be effective, which can prove challenging for some pet parents and their cats. In addition to feeding your cat prescription food, you must strictly monitor your cat's treats and prevent your cat from hunting for their meals while outside.

Some studies show that after three weeks of following a prescribed diet for cats with hyperthyroidism, levels of thyroid hormones begin to decrease. Within a few months, they may even return to normal levels.

What is the prognosis for cats with hyperthyroidism?

If the condition is diagnosed and treated early, the prognosis for cats suffering from hyperthyroidism is generally good. In some cases where the condition has become more advanced, 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.

Do you think your cat could have hyperthyroidism? Contact our vets in Novato to book an appointment.