Skip to Main Content
Ask About Financing

Hyperthyroidism in cats

As cats age, they may experience a condition known as Hyperthyroidism. In this post, our Seattle vets talk about the symptoms of hyperthyroidism in cats, how it is diagnosed and what the treatment options are.

What is hyperthyroidism in cats?

Hyperthyroidism is a condition that occurs when a cat’s thyroid glands become overactive. It’s a very common disorder caused by an increase in the production of thyroid hormones by the thyroid glands, which are located in the neck.

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.

When a cat is experiencing hyperthyroidism they will typically experience an increased appetite as well as weight loss due to more energy being burned. While these are a few of the effects of hyperthyroidism in cats there are some other signs to be aware of.

What are the common symptoms of hyperthyroidism in cats?

Hyperthyroidism in cats is typically seen in cats who are middle-aged and older typically cats that are at least the age of 10 with the potential to impact both male and female cats equally.

Some of the most common signs of hyperthyroidism in cats 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 as well as being overly warm and heat-sensitive which will most likely cause them to seek out a cooler place to lay.

In advanced cases, some cats may pant when they are stressed (an unusual behavior for kitties). While we note that most cats have a good appetite and are restless, some may feel weaker, lethargic or have a lack of appetite. If you notice any potential signs of hyperthyroidism or any other possible conditions in your cat then it is important to seek out veterinary attention as soon as possible. 

As with any disease or condition, the symptoms will get progressively worse as the condition is left untreated and could lead to further complications and be more difficult to treat. Other diseases can also complicate and mask these symptoms, so it’s important to see your vet early.

What are the causes of 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).

While it is hard to pinpoint the exact change that causes this condition in cats it is possible that a cancerous (malignant) tumor called thyroid adenocarcinoma is the underlying cause of this disease.

Are there any potential long-term complications of hyperthyroidism in cats?

It is possible for untreated hyperthyroidism to negatively affect the function of the heart, changing the organ’s muscular wall and increasing heart rate. This has the ability to eventually lead to heart failure which makes seeking treatment early incredibly important.

Another potential complication of hyperthyroidism in cats is high blood pressure, also known as hypertension, which 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.

As hyperthyroidism in cats typically affects senior cats it is also possible for your cat to be experiencing kidney disease at the same time. 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 in cats 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 Cat Clinic of Seattle, our Seattle vets are trained in internal medicine and have access to a variety of diagnostic tools and treatment methods.

A battery of tests will likely be needed to diagnose hyperthyroidism in your cat, as many other common diseases 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 is hyperthyroidism in cats treated?

Your vet may choose one of several treatment options for your cat’s hyperthyroidism, based on your pet’s specific circumstances and the advantages and disadvantages of each option. They 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 hyperthyroidism in cats?

The usual prognosis for hyperthyroidism in cats will generally be good with quick diagnosis and treatment including appropriate therapy, administered early. There where will be some occasions when potential 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 have a senior cat that this showing signs of hyperthyroidism or other concerning conditions? Contact Cat Clinic of Seattle to book a visit to have your cat assessed.

Welcoming New Patients

Cat Clinic of Seattle is welcoming new patients. Our compassionate vets are experienced in caring for cats in the Seattle area. Get in touch today to book your pet's first appointment.

Contact Us

(206) 633-1133 Contact