Dear Most Esteemed and Knowledgeable Kitties:
Hello. I am pretty sure my cat has hyperthyroidism. She has had it for a while now and a friend of mine says her two cats have it and the medication from the vet does nothing. What is your take on it?
Thomas: Well, Lisa, hyperthyroidism is a pretty common illness among senior cats. There are all sorts of beliefs about what causes the disease, from the scientific to the woo-woo, but we’re not going to discuss that here.
Bella: What we are going to do, though, is to tell you about thyroid medication and other treatments available for hyperthyroid cats.
Tara: I hope I don’t get hyperthyroidism, but I know that if I do, Mama will take good care of me, just like she takes good care of Thomas.
Thomas: In case you’re wondering, I myself am a hyperthyroid kitty. I’m on medication, and it’s working well for me.
Bella: The thing about hyperthyroidism is that it is a progressive disease, which means that the dosage of the medication may need to be increased over time. If your friend’s cats are hyperthyroid and the medicine isn’t doing anything, that probably means she needs to take them to the vet and have new blood work done. That way, she and her vet can see if the cats need more medicine.
Tara: That medication is called Felimazole–or methimazole, if you’re buying it at your local pharmacy rather than from your vet.
Thomas: Methimazole is used in humans to treat hyperthyroidism, which is basically when the thyroid glands produce too much thyroid hormone. This leads to weight loss, hyperactivity, excessive thirst and peeing, and behaviors such as crankiness.
Bella: The methimazole works by decreasing the amount of hormones the thyroid produces. Any hyperthyroid cat needs regular blood work and monitoring to make sure that their hormone levels are normal. If a cat has a “high normal” thyroid value on standard blood work, your vet may have a T3 suppression test done. (T3 is one of the hormones produced by the thyroid gland.)
Tara: We’d encourage your friend to go back to the vet and see if her cats just need a higher dose of medication.
Thomas: As for you and your cat, we also recommend that you take your kitty to the vet for blood work, especially since you suspect he may be hyperthyroid.
Bella: One thing you should know is that a lot of elder kitties have kidney disease as well as hyperthyroidism. And sometimes treating thyroid problems reveals kidney disease. You see, the overactive thyroid gland can compensate for some of the kidneys’ loss of function, and the two diseases share several symptoms, including excessive drinking and peeing.
Tara: The reason Mama chose to put Thomas on medication rather than do the “gold standard” treatment of radioactive iodine therapy is because he has kidney disease, too. It’s kind of a balancing act to make sure that both the hyperthyroidism and kidney disease are effectively treated.
Thomas: Speaking of radioactive iodine therapy, veterinarians call it the gold standard treatment because once a cat has it done, they should be cured of hyperthyroidism.
Bella: You see, the thyroid gland uses iodine, which usually comes from the meals we eat, to produce the hormones T3 and T4. Those hormones regulate everything from your mood to your heart rate and lots of other things.
Tara: Radioactive iodine therapy involves injecting a small amount of this radioactive iodine (I-131, in case you’re a chemistry nerd) into the bloodstream. It is then taken up by the hyperactive cells in the thyroid gland and destroys them, leaving only normal, healthy thyroid cells.
Thomas: An especially good thing about I-131 therapy is that it is also taken up by thyroid tissues that may be in other parts of the body, which can happen if the thyroid’s overactive cells happen to be cancer cells that then spread around the body.
Bella: The hard thing about I-131 therapy is that it’s expensive. It can cost $1,000 or more, depending on where you live. The good part is that once the treatment is done, your cat is cured. Most of the time.
Tara: And we say “most of the time” because Mama had I-131 therapy done on Siouxsie, and in her case it didn’t help. Mama even had her re-treated (the treatment center did this for free), but she was still hyperthyroid afterwards–so, she went on methimazole.
Thomas: The doctors at the radioactive iodine center said there are a few cats who simply don’t respond to the treatment for reasons nobody can really figure out.
Bella: But the vast majority of the time, it does work. Our cousin, Pedro, had radioactive iodine therapy last month, and he was totally cured!
Tara: But ultimately, Lisa, the medications for hyperthyroidism do work, as long as they’re given at the right dosage. Please let your friend know this. And you can be reassured that if your cat is hyperthyroid, you have options other than medications. We’d encourage you to have a good talk with your vet, get the blood work done, and from there, you and your vet can figure out treatment options.
Thomas: What about you other readers? Have you had a hyperthyroid cat? What treatment or treatments did you have done? Did they respond to treatment? Please share your stories to help Lisa and other people whose cats have hyperthyroidism.