What is it?

The thyroid gland is found in your cat’s neck, close to their windpipe. Thyroid hormones control the rate at which cells function. Excess thyroid hormone (hyperthyroid) makes the cells work too fast. This is a common condition affecting older cats and most are caused by a benign growth on the thyroid gland, a very small number will have a malignant (cancerous) thyroid tumour.

What signs will you see if you cat is hyperthyroid?

Each cat will present differently but most owners will notice:

  • Increased hunger
  • Increased thirst
  • Increased urination
  • Weight loss
  • Change to their coat (hair loss or failure to groom/matts)
  • Hyperactive nature/ restless
  • Increased vocalisation
  • Vomiting/ diarrhoea
  • Less commonly owners may notice their cat panting or difficulty breathing

How is it diagnosed?

A blood sample can diagnose hyperthyroidism

How can we treat it?

  1. Medical
    • Oral tablet medication given once or twice a day can help stabilise thyroid levels and reduce clinical signs associated with this condition.
    • These will need to be given for the rest of their life
    • Occasionally there are side-effects, as with any drug- ask your vet for more information
    • Regular blood tests are needed to determine that the medication dose is correct
  2. Surgical
    • Surgery can be done to remove the abnormal thyroid gland(s)
    • It is not a difficult procedure and can cure your cat permanently
    • It does require an anaesthetic and the risks should be weighed up in older cats.
    • Removing both thyroid glands can cause problems
    • The parathyroid glands that are next to the thyroid gland can be damaged during the surgery affecting your cats calcium balance- ask your vet for more information
    • Cats will require stabilisation first with tablet medication prior to surgery
  3. Radioactive iodine
    • Radioactive iodine can destroy the abnormal thyroid cells
    • It is an extremely effect treatment
    • It is injected under the skin like a vaccine
    • Your cat will need to spend some time in a special isolation facility while they eliminate the radioactivity via their urine and faeces before returning home
    • There is quite a long waiting list and it is an expensive treatment


Hyperthyroidism can mask kidney disease in older cats. Once they are stabilised we advise checking their kidney function as this is another common condition of older cats.