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Hyperthyroidism in cats - the skinny hungry cat

Hyperthyroidism in catsIs your older cat eating more than usual or demanding to be fed more often? Is your cat losing weight despite eating you out of house and home? Have you also seen a change in their behaviour? If your answers are yes then your cat could have hyperthyroidism.

What is Hyperthyroidism?

Hyperthyroidism in cats is commonly caused by benign nodules of the thyroid gland producing lots of thyroid hormone. Very rarely is it a malignant tumour (less than 2%).

Hyperthyroidism is one of the most common diseases found in middle-aged to older cats. The average age of hyperthyroidism in cats is 13 years old. Both females and males are equally affected and can occur in all cat breeds.

What happens to my cat with hyperthyroidism?

The most obvious sign is rapid weight loss even though cats appear happy and not in pain. Some cats may become more affectionate, while others can become more grumpy. They may vomit food often from eating too much and too fast.

Left untreated for a long time your cat may have difficulty walking because of muscle loss from weight loss. Most cats will eventually develop heart disease ranging from a mild murmur to severe congestive heart failure.

Hyperthyroidism can also cause hypertension (high blood pressure) which may lead to sudden blindness from damage to the retina in the eyes.

How do I know if my cat has hyperthyroidism?

Your vet may be suspicious your older cat could have hyperthyroidism if they have been losing weight despite a good appetite. Your vet may feel a lump in the neck and they may hear a very fast heartbeat with a murmur. Sometimes your cat may present with sudden blindness.

A simple blood test to measure the levels of a thyroid hormone (total t4) will confirm if your cat has hyperthyroidism.

My cat has Hyperthyroidism, can it be treated?

Yes, hyperthyroidism is treatable. The most common treatment is medication with an anti-thyroid tablet. This will require once or twice daily dosing life-long. Regular vet examinations and blood tests are performed to monitor your cat’s progress and if dosage needs to be adjusted.

Another treatment for eligible hyperthyroid cats is radioiodine therapy. Only vet clinics and hospitals with specialised licenses for ordering and handling radioiodine can perform this service. Your cat will receive a dose of radioiodine in the form of a capsule. The radioiodine will destroy the tumour and can mean a cure for your cat. Your cat will require boarding at the vet clinic or hospital for at least a week to reduce exposure of radiation to other people. A small number of cats may require another radioiodine treatment as they need a higher dosage to cure them.

A third option is surgery to remove the affected thyroid gland. There can be risk with surgery due to damage to the parathyroid gland which is next to the thyroid gland. Surgery is not recommended in hyperthyroid cats with secondary heart disease.


Will my cat be normal after treatment?

Once thyroid levels are normal most cats will stop losing weight and their hungriness may decrease. They may even start to put weight back on. Some cats may still have heart problems and hypertension (high blood pressure) if hyperthyroidism was left untreated for a long time.

Depending on the age of the cat and how early hyperthyroidism is treated, cats can still live a long happy life.

If you think your cat may have hyperthyroidism please contact us for an appointment or visit your nearest vet clinic.