Thyroid Disease in Cats: Signs, Causes & Treatment

Thyroid disease in cats (usually an overactive thyroid, known as hyperthyroidism) is a common hormonal condition in older cats. The signs aren’t always obvious at first. Your cat might lose weight even though they’re eating well, become more restless or vocal, or simply seem a little different from their usual self. Because these changes often happen as cats get older, they can be easy to attribute to ageing.

While the outlook will vary between individual cats, there is a range of management and treatment options available. Early diagnosis and vet care can help support your cat’s health and wellbeing.

Here’s what thyroid disease means for cats, the signs to look out for as a pet parent, and some of the approaches your vet may recommend to help manage the condition.

Table of contents

What is thyroid disease in cats?
What may cause thyroid disease in cats?
Signs of thyroid disease in cats
Could it be something else? Nighttime restlessness in cats
How is thyroid disease in cats diagnosed?
Treatment options for hyperthyroidism in cats
The role pet insurance can play in your cat’s care

What is thyroid disease in cats?

Your cat has a thyroid gland in their neck that produces hormones responsible for regulating their metabolism. An overactive thyroid is known as hyperthyroidism, while an underactive thyroid is known as hypothyroidism.

Hyperthyroidism (overactive thyroid)

Hyperthyroidism is the most common form of thyroid disease in cats and is most often seen in older cats. In most cases, hyperthyroidism is associated with a non-cancerous growth on the thyroid gland that causes it to produce too much thyroid hormone.

Hypothyroidism (underactive thyroid)

Hypothyroidism is rare in cats. When it does occur, it may be associated with the treatment for hyperthyroidism.

What may cause thyroid disease in cats?

There isn’t one clear-cut answer. Researchers still don’t fully understand why some cats develop hyperthyroidism and others don’t.

Some factors associated with hyperthyroidism include:

Benign thyroid growths: These are commonly associated with hyperthyroidism.
Age: The condition is most often seen in middle-aged and older cats.

In some cases, cancerous thyroid tumours can also cause hyperthyroidism, although this is uncommon.

Signs of thyroid disease in cats

While cats are known for being able to hide signs of pain or discomfort, hyperthyroidism can sometimes cause changes in their weight, appetite, coat appearance, or behaviour.

Physical signs

Common signs include:

Weight loss, even though your cat is eating normally or more than usual
Drinking and urinating more often
Vomiting or diarrhoea
A greasy, untidy, or matted coat
Increased heart rate

No single sign necessarily means your cat has thyroid disease. However, if you notice changes in your cat’s health or behaviour, particularly as they get older, it’s a good idea to speak with your vet.

Behavioural signs

An overactive thyroid doesn’t only affect your cat physically. It can affect their behaviour too. Some cats may become unusually restless or energetic, while others may become more vocal than usual.

You know your cat best. If you notice changes to their behaviour that seem unusual or out of character for them, it’s a good idea to speak to your vet.

Could it be something else? Nighttime restlessness in cats

Many cats are naturally active in the evenings, but if your cat has started pacing, vocalising, or becoming unusually restless at night, particularly if you’ve noticed other changes in their health or behaviour, it’s a good idea to speak to your vet.

Nighttime restlessness can have a range of causes, including medical and behavioural factors. It’s important to rule out any underlying health concerns before assuming it’s purely a behavioural issue.

If your vet gives them the all-clear, simple changes such as adjusting feeding times, and providing additional physical and mental stimulation through play and enrichment activities during the day may help everyone get a little more sleep.

How is thyroid disease in cats diagnosed?

If your vet suspects that your cat may have thyroid disease, they’ll usually start by considering your cat’s signs and symptoms and previous medical history, and carrying out a thorough physical examination. Blood tests may then be used to help assess your cat’s thyroid function.

In some cases, further testing may be recommended if more information is needed. Your vet will be able to explain which tests are appropriate for your cat and what the results mean.

Treatment options for hyperthyroidism in cats

There’s no one-size-fits-all approach to treating an overactive thyroid. Your vet will consider your cat’s age, overall health, any other medical conditions, and what’s practical for you.

There are several treatment options available for hyperthyroidism, including medication, radioactive iodine therapy, surgery, and dietary management. Your vet can help you understand the options and recommend the most appropriate approach for your cat.

Anti-thyroid medication

Medication may be used to help manage hyperthyroidism by reducing the amount of thyroid hormone produced by the thyroid gland. Regular monitoring may be recommended to help ensure treatment remains appropriate for your cat.

Radioactive iodine therapy

Radioactive iodine therapy is another treatment option for some cats with hyperthyroidism. Your vet can advise whether this approach may be suitable for your cat and what it involves.

Surgery (thyroidectomy)

Surgery to remove affected thyroid tissue may be considered in some cases. Your vet can discuss the potential benefits and risks of this option and whether it’s appropriate for your cat.

Dietary therapy

Some cats may be recommended a specially formulated diet as part of their treatment plan. If dietary management is being considered, your vet can advise on whether it’s suitable for your cat and how it should be fed.

Your vet can help you weigh up the options and decide what makes the most sense for your cat.

The role pet insurance can play in your cat’s care

A diagnosis of thyroid disease may mean your cat requires ongoing vet care. Depending on your cat’s individual needs, this may include monitoring, medication, follow-up appointments, or other treatment.

With the right pet insurance policy, you don’t have to face these costs alone.

Depending on your policy and its terms, RSPCA Pet Insurance may be able to help cover some of the eligible vet bills for your cat’s treatment. You can also customise your policy by choosing the annual cover limit, benefit percentage, excess, and optional extras that suit your pet and budget.

And with every policy supporting vital RSPCA animal welfare initiatives, it’s protection with purpose. For your own whiskered friend and thousands of others across Australia.

To learn more about how RSPCA Pet Insurance could support you and your pet, click here. Or, if you’re ready to take the next step, you can fetch a commitment-free pet insurance quote online.

Disclaimer

As with any insurance, terms, conditions and exclusions apply. Please read the Product Disclosure Statement to decide whether this cover is right for you.

References

[1] Cornell University College of Veterinary Medicine. Hyperthyroidism in Cats. Available from: https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hyperthyroidism-cats

[2] American Animal Hospital Association. Feline Hyperthyroidism. Available from: https://www.aaha.org/resources/2023-aaha-selected-endocrinopathies-of-dogs-and-cats-guidelines/feline-hyperthyroidism/

[3] American Animal Hospital Association. Feline Hyperthyroidism Therapy. Available from: https://www.aaha.org/resources/2023-aaha-selected-endocrinopathies-of-dogs-and-cats-guidelines/therapy-4/

[4] Merck Veterinary Manual. Hypothyroidism in Animals. Available from: https://www.merckvetmanual.com/endocrine-system/the-thyroid-gland/hypothyroidism-in-animals

[5] Sage Journals. Management and monitoring of hyperthyroid cats: a survey of Australian veterinarians. Available from: https://journals.sagepub.com/doi/10.1177/1098612X16634392

[6] RSPCA Australia. My cat is very active at night and keeps waking me up, what should I do? RSPCA Knowledgebase. Available from: https://kb.rspca.org.au/categories/companion-animals/cats/behaviour/my-cat-is-very-active-at-night-and-keeps-waking-me-up-what-should-i-do

FAQs

Common signs of hyperthyroidism may include weight loss despite a normal or increased appetite, increased thirst and urination, and changes in coat condition. Some cats also become more restless, vocal, or more active than usual. These signs can be subtle at first and are sometimes mistaken for changes associated with ageing, so regular vet check-ups are especially important as your cat gets older.

The outlook for cats with thyroid disease and the treatment options available will depend on the individual cat and their circumstances. However, there is a range of treatment options available for hyperthyroidism, and your vet can advise on the most appropriate approach for your cat. Hypothyroidism is very rare in cats and is typically managed under vet guidance.

Yes. Hyperthyroidism can affect a cat’s health and wellbeing if left untreated and may lead to other health problems over time, including effects on the heart and blood pressure. If you notice signs that could be linked to thyroid disease, it’s important to speak with your vet, who can assess your cat and discuss the most appropriate next steps.

It’s possible, but nighttime activity can have several causes and can also be part of normal feline behaviour. If your cat’s nighttime restlessness is new, seems out of character, or is accompanied by other changes such as weight loss, it’s worth booking an appointment with your vet.

If your cat is diagnosed with thyroid disease, they may require ongoing vet care, which can include monitoring, medication, or other treatment. Pet insurance may be able to help cover some of these costs, provided the condition isn’t pre-existing and meets the insurer’s policy terms and conditions.

With RSPCA Pet Insurance, you can also customise your pet’s cover to suit their needs and your budget by choosing your annual cover limit, benefit percentage, excess and any optional extra cover your pet may need. Every policy also supports the RSPCA’s animal welfare initiatives, helping to provide care and support for animals in need across Australia.

To learn more, visit the RSPCA Pet Insurance website or get a commitment-free quote online today.

As with any insurance, terms, conditions, and exclusions apply. Please read the Product Disclosure Statement to make sure this cover suits your needs.