top of page

Hyperthyroidism in cats- a quick guide

Updated: Jan 29, 2022

Hyperthyroidism is a condition that tends to affect older cats. It is caused by an over production of thyroid hormone. This is one of the more common conditions I see in older cats and thankfully it can controlled in the majority of incidences.

location of thyroid glands in cat, hyperthyroidism

The thyroid glands are positioned in the cats neck, one either side of the wind pipe. The majority of cats with an over active thyroid gland have a non cancerous tumour on the gland. In rare cases it can be causes by a malignant tumour.


There are many different signs that can affect organs all over the body. They usually worsen if the disease progresses or is left untreated.

skinny hyperthyroid cat

Here is a prime example of a typical hyperthyroid cat I would see in at the surgery. The signs and symptoms include:

  • Weight loss

  • Increased appetite

  • Increased fluid intake

  • Increased urination

  • Increased vocalisation

  • Greasy, scruffy coat

  • Vomiting

  • Diarrhoea

  • Hyperactivity/ aggression

  • Increased heart rate

How do I find out if my cat is hyperthyroid?

First thing do is book an appointment with your vet. They will examine your cat including feeling the thyroid glands to see if they feel enlarged. Other things that are often checked are the heart rate which is often increased, and the blood pressure.

If you vet is suspicious your feline friend has hyperthyroidism, a blood test will be preformed and this can diagnose the condition if the thyroid hormone levels are above normal range. These results are often available on the same day.

Hyperthyroidism can sometimes predispose your cat to other conditions. These include high blood pressure and heart disease so your vet may one to check for these conditions as well.

How can I treat my cat?

It can be a shock to hear your cat has a medical condition diagnosed and naturally you will worry. The good news is there a few options to help control this disease.

cute cat getting cuddles

Medication These are anti thyroid drugs which reduce the production and release of thyroid hormone. The medication does not cure the disease but helps control it. Your cat will likely need blood tests every so often to check the drugs are still working and the dose does not need altered. It is a life long treatment and given via tablets. If you cat is impossible to tablet or too nervous or aggressive to give blood then this may not be the best option. For many this option is stress free, easy and within budget.

Radioactive iodine therapy. This treatment is only available in specialist centres. The treatment involves an injection of a radioactive iodine. Iodine is used in thyroid hormone production so this radioactive type is used by the thyroid glands and the radiation destroys the abnormal thyroid tissue. It does not affect surrounding tissues. This treatment can take 1-2 weeks to work.

This method if treatment is actually a cure in most cases with no major side effects. During and for a number of days after treatment the cat needs hospitalised as will potentially eliminate radioactive material. Once this level has fallen to a safe level the cat can go home.

In 95% of cases the cat is cured within 3 months.

veterinary surgeons

Surgery Surgical removal of the affected thyroid gland can be preformed by your vet with a good Sucsess rate. it is likely to give a permanent cure so the cat will not require medication. Your cat would require a general anaesthetic so its general health is important when considering this option. A risk of this surgery is damage to the parathyroid glands which can then affect calcium levels in the blood.

Diet therapy Some studies believe limiting the iodine in the cats diet can help treat the disease. Personally I do not use this option as there are concerns that lack of iodine may cause other problems within the body. There is research on going with this treatment.


yawning silver tabby cat

Prognosis is generally good if the condition is treated and the cat responds well. I have had many cats live happily for years on the medication and also ones where the condition has resolved with either surgery or radiation. It is best to discuss in detail with your vet which option will suit you and your cat best and the costs of the different options.

11 views0 comments

Recent Posts

See All
bottom of page