I’ve been getting comments from folks that I write a lot about dogs and need to do some more feline-centric writing for a bit. So, this will be the first of several articles focusing on feline issues and disease. As one of the most commonly seen diseases, thyroid issues seemed like a good place to start.
The thyroid glands and the hormones they produce have the main purpose of controlling our metabolism. In times when we need to conserve energy, the brain will tell the glands to produce less hormone. This slows down the body’s internal functions and we will store calories. If we need to expend energy, the hormone levels increase, and the body begins burning more calories. In dogs, the issue is usually a chronically low thyroid level. In cats, their issue is almost exclusively a increase level of thyroid hormone that we call hyperthyroidism. We screen for this every 6 to 12 months with our normal blood screens so we catch it before it’s a problem.
The cause this is usually small tumors on one or both of the thyroid glands that are situated in the neck right in front of the windpipe. Initially, they are so small, that even trained vets have trouble feeling them. Now, when most folks hear the word “tumor”, they think cancer. However, in cats, these tumors are usually benign and only grow small amounts over long periods of time. Unfortunately, they are still producing excessive amount of thyroid hormone. The result is that the cat’s metabolism gradually increases. Think of it like putting your car in park and slowing giving it more gas. You’re not going anywhere, but you’re still burning through more & more fuel over time.
Without treatment, cats will develop weight loss, high blood pressure, heart issues, kidney damage, and many other issues. At high enough levels, they can encounter blindness, heart failure, and stroke. So, we want to treat this one early. Luckily, we’ve been treating this for a long time and have many options. The first is a medication that slows production of the hormone. Iodine is the primary component of thyroid hormone and is needed very little elsewhere in the body. The medication blocks the gland’s ability to absorb iodine to make the hormone. It is available many forms including pills, chews, liquids, and transdermal gels.
The second is a prescription diet that is very low in iodine. To date, there is only one diet that has been effective. However, the cat cannot have ANY other food or treats as even a small amount of iodine in different foods can allow the gland to start producing hormone again. This makes it a difficult choice in multi-cat households. You are also stuck if the cat doesn’t end up liking the food.
The last option is an actual cure. We are able to give a small injection of iodine that is slightly radioactive. This will get absorbed almost exclusively in the hyperactive gland tissue and destroy it. Ideally, the normal tissue is left behind and the cat can go back to living a normal life. In some rare cases it can take out a little too much glandular tissue and the cat may need a thyroid supplement. However, this is much easier and less dangerous than treating the initial hyperthyroidism.