Hyperthyroidism in Cats, What is it?

Hyperthyroidism in Cats

Hyperthyroidism is the most common hormonal disorder affecting cats. It typically affects cats older than eight years of age. Affected cats frequently have the peculiar combination of eating a lot more food, while at the same time losing weight. They almost always drink a lot more as well.  If left untreated, affected cats suffer from heart disease, high blood pressure and marked weight loss. The condition is life threatening.  Luckily, a variety of excellent therapies exist from tablets to surgery. This article gives a brief overview of the disease and the treatment options available.

What is hyperthyroidism?

The thyroid glands are located on either side of the windpipe and produce a hormone called thyroxine. Thyroxine is an important chemical does a great many things in the body but essentially gives you your “get up and go”.

A cat with hyperthyroidism produces way too much of this hormone which has a knock on effect on many areas of the body:

  1. Blood pressure
  2. Heart rate
  3. Kidneys
  4. Metabolic rate 

Blood Pressure

Hyperthyroid cats frequently develop high blood pressure which can cause problems for the heart and kidneys.

Heart Disease

This is one of the biggest problems as the increased amount of thyroxine causes the heart to beat faster and increase in size. Eventually this process (called cardiomyopathy) results in heart failure.

Kidney Disease

Sustained high blood pressure damages the kidneys. Very often these animals have underlying kidney disease which can complicate treatment.

Metabolic Rate

These cats are burning energy at a phenomenal rate so become very thin.

What Symptoms Will My Cat Have?

Cats with hyperthyroidism often have a characteristic set of problems you will notice:

  1. Weight loss
  2. Ravenous appetite
  3. Increased thirst
  4. Using litter tray more frequently to pass large volumes of urine
  5. Restlessness or hyperactivity
  6. Sickness and Diarrhoea
  7. Fast beating heart (you can often feel this on the outside of the chest)

How Do We Diagnose Thyroid Disease? Thyroid disease is diagnosed on the basis of symptoms and blood tests. 

Treatment of Hyperthyroidism? Hyperthyroidism can be managed in three ways:

  1. Tablets
  2. Surgery
  3. Radioactive Iodine Therapy

1. Tablets Tablet therapy can be useful, but you have to be able to give a pill twice a day for the rest of your cat’s life to be effective. Although this treatment option spreads the cost of treatment it costs a lot more to use tablets as pets require ongoing blood tests to monitor the success of therapy. So from a hassle and cost perspective this is not always the best option.

2. Surgery to Remove the Affects Glands(Thyroidectomy)  Surgical removal is also possible and frequently effective way to treat the disease. However there are risks and complications involved in anaesthetising an elderly cat with heart disease (which is frequently the case with hyperthyroid cats). 

3. Radioactive Iodine Therapy This is the best treatment option for cats with an overactive thyroid gland. It is safe, effective in almost all cases and has few in any side effects. It involves the giving a dose of a mildly radioactive iodine isotope to your cat. At Double Bay Vet Clinic this is given as an oral capsule.  Because the thyroid gland is the only gland in the body that uses iodine the radioactive particles concentrate within the thyroid gland and the radiation emitted destroys only the overactive thyroid tissue. The rest of the body is unharmed - making it a wonderfully targeted therapy. Only a small number of facilities offer radioactive iodine treatment and cats are required to stay hospitalised at the facility for a few days following treatment. Double Bay Vet Clinic is one of these facilities.

What is the Long-term Outlook For my Cat?

In most cases it is excellent. But the outlook for cats suffering from hyperthyroidism depends very much on the time of diagnosis and whether any other diseases are present. In many cases, if the problem is diagnosed quickly the treatment will cure the problem. The trick is to get your pet checked out by your vet as soon as you see any of the symptoms described above. This article is for information only and should not be used as a substitute for veterinary advice. If you are worried about your pet’s health contact your veterinary surgery for advice.