|Photo: West Zest|
Cats are hyper, therefore they become hyperthyroid while dogs most commonly become hypothyroid. I know it's kind of a silly way to remember, but it helped me out as a new technician. So, what is a thyroid anyways?
Thyroid is an endocrine gland found in your pet's body. People have them too, of course. The thyroid gland has some very important jobs like controlling how quickly the body uses energy, makes proteins, and controls the body's sensitivity to hormones.
Hypothyroidism in Dogs
If a dog is diagnosed with hypothyroidism, it means that their thyroid gland isn't producing enough thyroid hormone. This causes a very slow metabolism usually resulting in excessive weight gain. It can also cause a dog to have an un-thrifty coat that causes poor hair re-growth after a dog has been shaved or clipped. Their skin may also appear dry, thick, and leathery.
If a dog is going to become hypothyroid, it will usually happen mid-life. Diagnosis of hypothyroidism in dogs is pretty simple and only requires a blood test called a "total T4". If the test shows low thyroid levels, an even more precise test may be run afterwards called a "free T4 by equilibrium dialysis". Or for short you could just say FT4 by ED if you like.
If the blood test confirms that the dog has a hypo-active thyroid, the next step will be a prescription of thyroid supplements for the dog. This supplement, called levothyroxine, is usually prescribed by a veterinarian to be taken once or twice a day for the rest of the dog's life. Hypothyroidism in dogs is permanent. The supplements usually come as flavored tablets making it easier to medicate you pup. Regular thyroid blood checks and exams will be performed throughout a hypothyroid dog's life to make sure that they are not being over-supplemented.
So can dogs become hyperthyroid?
The answer is yes - but it's extremely rare. If a dog comes down with hyperthyroidism, the most likely causes are cancer of the thyroid gland or over-supplementation of thyroid hormones. That's why it's important to have your hypothyroid dog's hormone levels checked regularly - to make sure that they are receiving the right dosage of medication. Otherwise, you could be making them hyperthyroid.
Hyperthyroidism in Cats
|Hyperthyroid Cat. Photo: aturkus|
As you may have already guessed, hyperthyroidism means that the thyroid gland produces too much thyroid hormones. As mentioned above, this condition affects mostly cats rather than dogs. There are several tell-tale symptoms of hyperthyroidism in cats. Excessively meowing for food, ravenous appetite, and weight loss. Some cats may also have a poor looking coat, experience excessive thirst, and more frequent urination.
Hyperthyroidism usually affects cats who are older than 10 years. In most cats, diagnosis is easy and requires a simple blood test like the one mentioned for dogs. A very small percentage of cats will show a normal thyroid level for this test even though they are hyperthyroid. This makes it more difficult to diagnose a handful of cats with hyperthyroidism.
What are the treatment options for hyperthyroidism in cats?
There are more options available in the treatment of hyperthyroidism in cats than hypothyroidism in dogs. There is a daily medication called methimazole which is given orally although, this medicine does have its side effects. Side effects of the drug could include vomiting, itchiness, jaundice, loss of appetite, and lethargy. A small percentage of cats will experience these side effects from methimazole.
Another treatment option is a methimazole ear gel which is applied topically everyday. Many cat owners find this method easier than giving pills to their cat on a daily basis. The ear gel is applied to the skin on the ears and absorbed into the body. Of course, it can cause hair loss on the ears along with the other symptoms of methimazole. Cats who take methimazole will need to have their blood chemistries checked on a regular basis.
|Cat at the vet. Photo: Andrew Ciscel|
The best treatment option for hyperthyroidism in cats is radioactive iodine therapy. After a cat has this treatment, they are no longer hyperthyroid. Radioactive iodine is injected under the skin and eliminates the hyperactive tissue in the cat's thyroid gland. No thyroid medication is needed after this treatment. Cats who receive this treatment will have to be kept at the facility for a little while until the radiation levels in their body and waste come down. It's usually not more than 2 weeks however.
Radioactive iodine therapy may be a little expensive, but the cost is probably well worth it in the end. The cost of medication adds up over time. Plus, it is more convenient than having to pill your cat everyday for the rest of their life. Something both of you will probably be happy to live without.
Can cats become hypothyroid?
Like dogs, cats can very rarely become hypothyroid. The most likely feline candidates for hypothyroidism are cats who have had a radioactive iodine therapy treatment. Hypothyroidism is not life-threatening, thankfully. If a cat were to become hypothyroid, the treatment would be the same supplement that dogs receive - levothyroxine.
Last month, I read a couple of good posts about thyroid conditions in cats on some other blogs. One was from A Tonk's Tail and talks about the rare condition of hypothyroidism in cats.
The other was a series of 3 posts by Mizz Bassie's mom from The Bassie Bulletin. Her cat, Surfeit, was diagnosed with hyperthyroidism and had radioactive iodine therapy treatment. They are a great first-hand account of experiencing hyperthyroidism in cats with a lot of good information. Follow the links to read their story.
- Part I: Surfeit is Hyperthyroid
- Part II: Hyperthyroidism in Cat, continued: Treatment
- Part III: Surfeit Gets Radioactive Iodine