Hyperthyroidism in cats

What is hyperthyroidism?

Hyperthyroidism is a common condition in older cats where the thyroid glands produce too much thyroid hormone. This can make the body work harder than it should and may affect several organs over time.

In most cats, this happens because the thyroid glands become enlarged and overactive for a non-cancerous reason. Thyroid cancer is uncommon.

What are the symptoms of hyperthyroidism?

Hyperthyroidism usually affects middle-aged to older cats. The early signs can be easy to miss, but some of the more common things owners notice include:

• Weight loss despite a normal or increased appetite
• Increased thirst and urination
• Restlessness, irritability, or vocalising more
• Vomiting or diarrhoea
• Poor coat condition, weakness, or muscle loss

Without treatment, hyperthyroidism can put extra strain on the body and may lead to complications such as:

• High blood pressure
• Heart disease
• Kidney disease
• Serious illness if multiple organs are affected

Hyperthyroidism and kidney disease

Hyperthyroidism can increase blood pressure and place extra strain on the kidneys. In some cats, underlying kidney disease only becomes more obvious once treatment begins, which is why ongoing monitoring is such an important part of care.

How is it diagnosed?

Your veterinarian will usually diagnose hyperthyroidism with a physical examination and a thyroid blood test. If the results are not clear straight away, repeat or additional thyroid testing may be recommended.

Because hyperthyroidism can affect other parts of the body, your veterinarian may also recommend blood and urine tests, blood pressure checks, and ultrasounds to help build the clearest picture of your cat’s overall health.

How is it treated or managed?

The good news is that with the right treatment and regular monitoring, many cats with hyperthyroidism can continue to enjoy a very good quality of life. The best option will depend on your cat’s health, lifestyle, and how easy they are to medicate.

Treatment options your veterinarian may discuss with you include:

Radioactive iodine (I-131) therapy

This is a single injection given at a licensed facility and is generally considered the most effective treatment. Most cats do not need further treatment afterwards, although follow-up blood tests are still important.

Anti-thyroid medications

Tablets or topical medications can be a very good long-term option for many cats. These ongoing treatments help control the condition but do not cure it, so regular check-ups and blood tests are important.

Dietary therapy

An iodine-restricted prescription diet may help control thyroid hormone levels in some cats, but it needs to be fed exclusively and long-term, with no other food or treats.

Surgery (thyroidectomy)

Surgery may be considered in some situations, especially if other treatments are not suitable or if thyroid cancer is suspected.

If your cat is showing any signs of hyperthyroidism, we recommend booking an appointment with your local Animates Vetcare clinic for a thorough check up.

Article disclaimer: The above information is provided for pet owner education only and not intended or implied to be a substitute for professional veterinary medical advice, diagnosis or treatment from a veterinarian. Animates Vetcare disclaims liability for any damages or losses, direct or indirect, that may result from the use of or reliance on information provided in this article. If you are concerned your pet may have a health condition, please contact your local veterinary clinic for advice.