Hyperthyroidism in cats

Veterinarians get frustrated sometimes. It seems like cats only come into the veterinary clinic for three reasons; weight loss, lethargy, and vomiting. No matter what is wrong with the cat, it seems like they almost always have one or all of these signs. Hyperthyroidism is one of the diseases that also have these symptoms. Cats suffering from this usually lose weight, even though they are eating more. They can be lethargic or extra-excitable. Sometimes the cat will drink more water (usually noticed because they urinate more) and can have vomiting and/or diarrhea. The owner subsequently brings the cat in to see a vet because it is sick.

Hyperthyroidism is always on the list of possibilities when these symptoms occur. Hyperthyroidism is a very common disease in older cats. It is so common that most vets will test the thyroid every time a sick cat comes in. It is a disease that can be easily treated, but it will slowly kill the cat if it is not treated. Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone. This is as opposed to hypothyroidism, where the thyroid gland doesn’t produce enough thyroid hormone. Hypothyroidism is common in older dogs and rare in cats. Hyperthyroidism is common in older cats and is rare in dogs.

The thyroid gland is located about halfway down the neck. There are two thyroid glands, one on each side of the throat. The thyroid gland produces thyroid hormone. Thyroid hormone is important for all body functions. It allows the body to maintain an energy balance; that is, thyroid hormone is involved in keeping the metabolism at the proper level. Have you ever met someone (humans can suffer from hyperthyroidism as well) with a high metabolism? They are full of energy, very skinny, and can eat all day long without gaining weight. This is what happens to a cat with hyperthyroidism. Their body is simply not storing calories and therefore they never gain weight. Your veterinarian will test thyroid hormone levels to determine if your cat has hyperthyroidism. If your cat has high levels of thyroid hormone in its blood, it is very likely that it has hyperthyroidism.

There are a few different ways to treat this disease. It can be treated surgically or medically. To treat hyperthyroidism surgically, the vet will go in and remove part of the thyroid gland which is a very effective procedure. Once your cat has part of its thyroid gland removed, it will probably have to be on thyroid hormone pills for the rest of its life. This is because usually the remaining part of the thyroid gland is unable to produce enough thyroid hormone.

There are two ways to treat hyperthyroidism medically. Your cat can be given ‘radioiodine therapy’. This is simply a drug that is bound to iodine. Iodine is what the thyroid gland uses to make thyroid hormone, so when the gland takes up this radioiodine, the drug kills some of the thyroid gland cells. This procedure is very safe. The other medical way to treat hyperthyroidism is with a drug that prevents the gland from making thyroid hormone. There are a few different drugs that work this way. Your cat will be on these drugs for life, and will have to have its thyroid hormone levels measured every couple of months.

When your cat comes into the veterinary clinic, and it is diagnosed with hyperthyroidism, don’t worry! This is a very common disease in older cats. It is easy to treat, and is not terribly expensive. It is very important that you do not wait until your cat is very sick before you bring it in though. Like any disease, the sooner you catch it, the faster you can make your cat happy and healthy again.

By Ashley O’Driscoll – Pets.ca writer