Hyperthyroidism can be a problem in middle-aged and senior cats. Our Stroudsburg veterinarians explain the disease, symptoms, diagnosis, and treatment options in this post.

What is hyperthyroidism in cats?

Hyperthyroidism occurs when the thyroid glands of a cat become overactive. It's a very common disorder caused by an increase in thyroid hormone production by the thyroid glands in the neck.

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

Cats with hyperthyroidism tend to burn energy too quickly, resulting in weight loss despite eating more food and having an increased appetite. More symptoms will be discussed further below.

What are the symptoms of hyperthyroidism in cats?

Usually seen in cats who are middle-aged and older. Most are older than 10 - between 12 and 13 years old - when the disease becomes an issue. Female and male cats are equally impacted.

Hallmark signs of hyperthyroidism 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 keep an eye out for any significant changes in your cat and have them addressed as soon as possible.

These symptoms are usually mild at first and gradually worsen as the underlying disease worsens. Other diseases can also complicate and mask these symptoms, so it's critical to see your veterinarian as soon as possible.

What causes hyperthyroidism?

Most kitties' conditions are caused by benign (non-cancerous) changes in their bodies. Both thyroid glands are frequently involved and enlarge (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). Thyroid adenocarcinoma, a cancerous (malignant) tumor, is the underlying cause of this disease in rare cases.

What are the long-term complications of hyperthyroidism?

Left untreated, hyperthyroidism can impact the function of the heart, changing the organ’s muscular wall and increasing heart rate. It can eventually lead to heart failure.

High blood pressure is another potential complication (hypertension). Though this occurs less frequently, it can cause damage to several organs, including the brain, kidneys, heart, and even the eyes. If your veterinarian diagnoses your cat with hypertension in addition to hyperthyroidism, blood pressure medication will be required.

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 tricky. Your vet will complete a physical exam and palpate your cat’s neck area to look for an enlarged thyroid gland. At Barton Heights Veterinary Hospital, our Stroudsburg vets are trained in internal medicine and have access to a variety of diagnostic tools and treatment methods.

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 will most likely be required to diagnose hyperthyroidism in your cat.

A complete blood count (CBC), urinalysis, and chemistry panel can aid in the diagnosis of kidney failure and diabetes.

A simple blood test revealing elevated T4 levels in the bloodstream may be sufficient for a definitive diagnosis, though this is not true for all cats due to concurrent illnesses or mild cases of hyperthyroidism, which can result in fluctuating T4 levels 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?

Your veterinarian may recommend one of several treatment options for your cat's hyperthyroidism, based on your pet's unique circumstances and the benefits and drawbacks of each option. They may include the following:

  • 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 are the prognosis and life expectancy in cats with hyperthyroidism?

Your cat's prognosis for hyperthyroidism will be generally good if appropriate treatment is started early. Complications with other organs can worsen the prognosis in some cases. Fortunately, unless they develop another disease, most cats with uncomplicated hyperthyroidism will live for several years after treatment.

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 suspect your cat is suffering from hyperthyroidism? Contact Barton Heights Veterinary Hospital for an examination!