Health

Cats

Overactive thyroid (hyperthyroidism) in cats

Hyperthyroidism happens when the thyroid gland in the neck makes too much hormone, speeding up the body. It mostly affects middle-aged and older cats. Left untreated it can damage the heart and cause high blood pressure, but it can be treated well once diagnosed with a blood test.

What you might notice

• Weight loss despite a big appetite.
• Drinking and urinating more.
• Restlessness, being noisy or demanding.
• Vomiting or diarrhoea.
• Untidy, greasy or matted coat.

Common causes

• Usually a non-cancerous overgrowth of one or both thyroid glands.
• Most common in middle-aged and older cats.
• The exact trigger is not fully known.

What you can do at home

• Weigh your cat regularly and record the results.
• Note changes in appetite, thirst and behaviour for your vet.
• If treatment is prescribed, give it exactly as directed and keep check-up appointments.

Book a vet in the next day or two if

• Weight loss in an older cat, especially with a good appetite.
• Increased thirst or urination.
• New restlessness or night-time crying.

Don't

• Do not assume weight loss is normal in an older cat.
• Do not stop or change prescribed treatment without talking to your vet.
• Do not give human medicines or supplements to a cat.

Prevention

• There is no proven way to prevent it; early detection at senior check-ups is key.
• Have older cats weighed and examined at least once a year.
• Report weight loss, more thirst or restlessness to your vet early.

This guide gives general information about common health problems in dogs and cats. It is not a diagnosis and it does not replace an examination by a veterinarian. Every animal is different, and signs that look mild can sometimes hide a serious problem, especially in cats, which often hide illness and pain. If you are worried about your pet, or if your pet shows any of the warning signs listed here, contact your vet or the nearest emergency veterinary clinic straight away. Never give your pet human medicines or any medicine not prescribed for that animal by a vet.