What is feline hyperthyroidism?

As cats get older, one illness they risk is hyperthyroidism, a problem with the thyroid glands of the cat in which these glands enlarge and start producing a greater amount of thyroid hormones than usual. The enlargement is caused by a tumor, but it is nonmalignant in the vast majority of cases.


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What are the symptoms?

The change in the hormonal balance of the cat caused by the increased hormone production can affect a number of other organs and cause a variety of symptoms. Some of the most common ones are alteration in the cat's appetite (either an increase or a decrease can happen), increased thirst, loss of weight, heart disease or feline heart murmurs, or problems associated with digestion such as your cat vomiting or your cat getting diarrhea. They may also get high blood pressure and other heart related problems. Your vet will conclusively diagnose the cat based on a test for the levels of thyroid hormones in the cat, and they will be able to tell based on whether they are abnormally high.

What causes it?

Usually age is the prime factor. As cats age, stuff in their bodies starts to go wrong, and this is one of them. The risk of hyperthyroidism may be affected by how the cat has lived, whether it is obese, and other unknown factors, but getting old is the main reason. It's not something that is contagious or that can hurt your other cats.

What is the treatment?

There are a number of treatments, and which one your vet uses will depend on your cat's specific medical situation. Sometimes specific drugs are used to combat the problem, including Tapazole for cats and others that will reduce the production of thyroid hormones. Surgical removal of the thyroid gland is also done in many cases, because cats usually have two functioning parts of the gland and often only one is affected. Another treatment is essentially radiation therapy using iodine. Iodine is a mineral found in salt, and it is only used by the thyroid. The body thus moves any iodine into the thyroid, allowing treatment using mildly radioactive iodine that concentrates in the thyroid and does not affect the rest of the body.

Depending on what happens with the treatment, you may also have to use medication to supplement thyroid hormone production in the cat. For example, if the entire thyroid is surgically removed, the cat may need another source for normal levels of the hormones. You may also need to get the cat treated for any secondary problems that have been caused by the abnormal hormonal levels. 

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