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Cat hyperthyroidism: identifying thyroid problems in your cat reading-time-icon 2 min read

Much like humans, cats can suffer from two types of thyroid problems: hyperthyroidism – where the cat produces too much of the hormone, and very rarely - hypothyroidism, where the cat doesn’t produce enough.

An overactive thyroid is relatively common in older cats.  On its own it is not a particularly serious disease, but often leads to secondary problems, such as heart disease and high blood pressure, which are more severe.

The technical bit…

Thyroid conditions are classed as diseases of the endocrine (hormonal) system. Also called thyrotoxicosis, hyperthyroidism is caused when the thyroid gland in a cat’s neck produces too much thyroxine – a thyroid hormone that controls the body’s metabolism.

The causes of hyperthyroidism in cats

Scientists don’t know what triggers feline hyperthyroidism, but it’s possible that it’s caused by either too much or too little of certain compounds in the cat’s diet, or overexposure to thyroid-disrupting chemicals. It may be caused by a tumour, but this is rare.

“Hyperthyroidism is relatively common in older cats. While it’s not particularly serious, it often leads to more severe conditions – so it’s important to visit your vet for advice.”

Recognising the signs of hyperthyroidism in cats

Cats with hyperthyroidism may gradually develop signs and symptoms that can also indicate other conditions. If your cat displays any of the symptoms below – or if you have any reason to think they’re suffering from a thyroid condition – always take them to your local vet.

The symptoms of hyperthyroidism in cats include:

  • Weight loss
  • Increased hunger
  • Increased thirst
  • Increased urination
  • Diarrhoea
  • Vomiting
  • Hyperactivity
  • Increased vocalisation

Diagnosis and treatment of hyperthyroidism in cats

If your local vet suspects your cat has an overactive thyroid (or in rare cases, an underactive thyroid), they may recommend a simple blood test to confirm their diagnosis.

An overactive thyroid in cats (feline hyperthyroidism) can often be managed with medication, which doesn’t cure the condition, but controls it. Alternatively, your vet may advise referral for radioactive iodine therapy, and can give you full details of this treatment if he or she thinks it’s the best course of action for your cat.

Some cats need surgery to treat hyperthyroidism, but this is rare. Your vet will always talk you through any treatment they’re recommending, to put your mind at rest.

Need advice on hyperthyroidism in cats?

For expert advice and information on an overactive thyroid in cats, get in touch with your local vet. 

Find your nearest vet using our Find a Vet page, or speak to a vet online using Online Vets.