Cat Hyperthyroidism

irishdancersgramJanuary 10, 2006

Does anyone have a cat with Hyperthyroidism and what kind of treatment has your's required? I've had my Clancy,(3 yr. old neutered tabby) to the vets a few times and they can't seem to find his problem, so I'm researching on line...To me, all his symtoms point to Hyperthyroidism and find it hard to believe, the vet hasn't said the same thing. I'm seriously thinking of seeking out a new vet.....Any help will be appreciated.....


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I'm a vet tech at a place that does radioactive iodine treatment for hyperthyroid cats, and a vet student, so I have LOTS of experience with it.

First of all, you need a diagnosis before you go off trying to treat him. All that takes is simple bloodwork for a T4. Either it will be high or it won't.

If it's borderline, there are other tests that can be done to determine if Clancy (I hope he's orange!) is hyperthyroid. One is a Tc99 scan. That has to be done at a facility like a vet school that has the equipment, but it is very diagnostic. If Clancy is hyperthyroid, it will be obvious.

You could also do additional bloodwork (free T4, TSH) but honestly that seems to confuse more than help.

If he is truly hyperthyroid, the best treatment is the radioactive iodine injection. It's very simple, just a quick shot under the skin like a vaccine, then he has to "cool off" for a certain amount of time until he is no longer radioactive. The cooling off period varies by state regulation; here in NC it's at least 3 days that he would have to stay in an isolation area before going home. The radioactive iodine is taken up by the active (diseased) thyroid tissue (and no other tissue in the body) and destroys it. Cats are lucky in that when they become hyperthyroid, it is usually a goiter that has gone crazy producing too much T4, and the rest of the thyroid tissue doesn't do anything because of negative feedback. That's how only the diseased tissue is destroyed. After the treatment, which is over 95% successful, he won't need anything other than a couple of T4 tests (usually at 30 and 90 days post-treatment) to monitor his progress. Then just once a year or so with his annual physical exam/bloodwork. The disadvantage of I131 treatment is the cost- usually about $1200.

The second treatment option is medication. It's available by pill or by transdermal gel. The brand name is Tapazole; generic is methimazole. It is less expensive at first, but requires T4 tests to adjust the dose of medication. Then once he's stable, you have to do quarterly (or so) T4 tests to make sure the dose doesn't have to be adjusted. Also, methimazole is liver toxic, so you also have to monitor liver enzymes. Some cats cannot take methimazole because it makes them vomit or because they develop a very serious puritus that causes them to scratch their faces to the point of bleeding. And finally, with Clancy being so young, by the time you paid for the medication and monitoring for about 2-3 years, you could have had the radioactive iodine treatment done for the same cost. Methimazole is life-long, so that's giving a cat a LOT of pills or ear goo twice a day.

The third treatment option which you may hear about but isn't recommended is surgery. Usually surgery is not recommended because hyperthyroid cats tend to be much older than Clancy- the mean age at the hospital where I work is 15. At that age, many cats have other problems that make them bad candidates for surgery. The other reason that surgery is not recommended is that there is thyroid tissue scattered throughout the body, not just the glands in the neck. We have had cats with both neck thryoid glands removed still require the radioactive iodine treatment because it wasn't the glands that were the problem. Also, you would need to find a very experienced surgeon, because if the parathyroid glands are accidently removed with the thyroid glands, calcium regulation is not longer possible and that leads to a whole host of serious life-threatening complications. Last time I heard, the surgery costs about 1/2 of the radioactive iodine treatment, but with all the risks and the very real possibility that it wouldn't even solve the problem, it just isn't done so much any more.

All that said, 3 years old is awfully young to be hyperthyroid. Not that it doesn't happen; I remember treating an 18 month old Siamese, but that cat had very significant health issues besides hyperthyroidism.

What is Clancy doing that makes you think he's hyperthyroid? Has a T4 been run?

    Bookmark   January 10, 2006 at 4:44PM
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I have a 12 year old neutered orange tabby with hyperthyroidism. I elected to put him on Tapazole and he has done very well with it (1/4 pill 2X day).
I chose not to go with the radioactive therapy because he is an extremely "hard to handle" kitty at the vet and my vet said that was an issue of consideration. I thought the treatment would be too traumatizing for him and decided to try the medication first.

If your kitty is sick and hasn't had any bloodwork I would look for another vet. My kitty suddenly got very ill. My vet ran a blood panel and then ran more tests (I believe free T4 was one of them) when certain levels were off. She suspected hyperthyroidism after the first tests but ran additional tests for a more concise diagnosis.

My cat has to be gassed to draw blood. Jack is a total sweetheart at home but the minute he is on the exam table look out. That is the main reason I tried medication over radioactive treatment. Fortunately my vet got his dosage regulated fairly quickly (it had to be lowered once from the initial dose) and he has adapted well.

It is a tough decision but there is no wrong or right answer. You just have to do what you think is best for your kitty. But first you need a diagnosis. Best of luck to you and your kitty and please keep us posted.

    Bookmark   January 10, 2006 at 11:19PM
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WOW, what great information...Meghan, Clancy is indeed an orange tabby and although we have 3 other furbabies, he's my baby...Clancy is always hungry, wants to eat all the time, eats real fast and then will cry or make loud noises, and he's also a up-chucker. The vet thought it might be a sensitive stomach and we watched what we fed him, giving him little portions more often. When that didn't help, they thought, IBS and put him on steriods but he was no better. They did want to do the scope but honestly, we can't afford it. He has had blood work done, but they have never mentioned Hyperthyroidism.....I am making an appointment with another vet and hopefully we'll find out what's wrong....Thanks again for the great responses.....

    Bookmark   January 11, 2006 at 4:12PM
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Well, steroids have this nasty little side effect of making you hungry all the time. Yep. Probably made him worse.

Sensitive stomach is a reasonable thought for a young cat; so is IBD. I can understand why they're thinking along those lines, but if it quacks like a duck and walks like a duck... Plus a blood test is so much less expensive and less invasive than endoscopy. Rule out the easy stuff first.

What food is he on now? I ask because my husky Aleksander has food allergies. One of the foods his allergist suggested was Hill's Z/D because it is actually hypoallergenic, as opposed to most other food allergy diets which rely on novel proteins. I tried it for 1 20# bag. It was awful. Aleks was hungry all the time, very irritable, hyperexcitable, drank all his water every day (he isn't a big drinker), peed and pooped in the house, all kinds of things. I doubled his food ration and he still lost 5# in 3 weeks. I told his allergist about it, and she said that she was starting to hear similar things with some other clients, so she stopped recommending it. I was almost ready to test him for hyperthyroidism, which is extremely rare in dogs (and almost always cancer). I have no idea what was in (or not in) that food to make him like that, but I feed him fresh home-cooked meals now. No problems with allergies or craziness now. Aleks also can't have any of the dry Science Diet foods because they contain preservatives (BHA and BHT) that don't agree with him (diarrhea).

Just thought I'd offer the food allergy/sensitivity to something theory in case he's been on something similar. It took a long time for me to figure out the preservative thing. He can eat poultry, venison, and fish-based diets OK, but beef and especially lamb are no good.

Clancy is the perfect name for an orange tabby. If I could have a cat, it would be a male orange tabby with a good Irish name (Danny Boy is right up there). But DH is extremely allergic to cats, boo hoo.

Keep us posted on how the new vet is and the results.

    Bookmark   January 11, 2006 at 5:42PM
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My 16 year old Barney was diagnosed with hyperthyroidism last spring. I had switched vets as I didn't feel confident in the one they were going to (the last physical exam she gave him was cursory at best) and they now go to a cat's only vet clinic that is just up the street from our province's veterinary college. As soon as the new vet saw Barney and felt him, she noted that he had the obvious signs of weight loss (in 2001 he was 16lbs and when she weighed him he was 12 lbs) but she also noted that he'd lost muscle tone, which apparently is a huge red flag for hyperthyroidism. He would eat his crunchy food like a pig but wasn't gaining weight, he was throwing up too, he was also very hyper - he'd tear around then stop to wash himself, tear around some more then stop to wash...see the pattern? He also has a heart murmer, but he's had the murmer for years (I think I first found out about it 10 years ago). Murmer apparently is a classic sign of hyperthyroidism.

We elected for medication as well as opposed to the radioactive iodine - Barney is a very social cat and the way the vet described it, he'd go to the lab at the vet college where he'd have his treatment, be segregated for 1 to 2 weeks, then come home but would have to continue to be segregated until his radioactivity dissipated - that's just not something we could put him through. So he's on Tapazole 1/2 pill in the am and 1/4 pill in the pm. He's gotten very good about taking them, I think he knows he feels better. He's not the hyper crazy thing he once was, he's much quieter, though that could be age related. He eats and his weight is stable. He has his T4 numbers tested often - I think they are doing it again at the end of the month. He's also on a medical diet, vet only food (our other cat is in the early stages of kidney disease so they are both on vet food).

Definitely a T4 test will tell you if Clancy has this condition. And at his age, if I were you I would opt for the radioactive treatment. It will be costly, I think we were looking at $1500 or something like that, but in the long run it would be better.

Good luck finding a new vet. If you haven't settled on a clinic already, maybe seek out a cat's only vet. It's so nice being able to go to a vet that does nothing but cats - it's less stressfel for them for appointments and the vets are specialists in feline medicine as opposed to having to know everything about all animals.


Here is a link that might be useful:

    Bookmark   January 12, 2006 at 1:17PM
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I have to ask - is it merely a coincidence that all three of our cats with hyperthyroidism are orange tabbies??

    Bookmark   January 12, 2006 at 11:39PM
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Renee, You know, that is weird....
Meghan, Clancy is mostly on Fancy Feast but sometimes gets Friskies...He will not eat dry food as the other cats do and I hardly ever see him drink water. With any of the food, if it's chunks, he seems to have a hard time eating or chewing. (The vet had checked his teeth). I did hear Fancy Feast is stronger or richer than most and sometimes that will cause the upset stomach. I've even tried giving him certain jars of baby food, but that didn't last long. Mealtime at our house is crazy. Clancy is a real stinker, I try to feed all the cats at the same time, each has their own dish, and he will start eating, look around and then make nasty noises and the others will run away and then he thinks he can finish theirs...Simba, our Persian prince, wants to eat in the living room and will go to his spot and wait until you bring it to him.
The last couple of days, Clancy has been fine, no real yelling or upchucking, but will see the new vet soon.....

    Bookmark   January 13, 2006 at 4:49PM
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Well, wet food is better for them anyway. FF is a bit rich, but that stuff is like kitty crack- they sure do get hooked. It would be hard to switch foods on him. Wouldn't want to do it while his health is at all questionable anyway as he may refuse to eat new food. Glad you're going to get him checked out by another vet.

    Bookmark   January 13, 2006 at 7:40PM
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Hi all,

I've been searching for info to try to figure out why my 13 year old ORANGE TABBY is losing weight. I've had him to the vet and checked for parasites and a complete blood profile that was entirely normal - no kidney, liver, diabetes problems; also a thyroid test and thyroid was normal. He eats well and acts normal and happy - he seems hungrier even though I give him extra food between his normal two meals per day. How likely is it that these kinds of tests would have a false negative? Is a repeat warranted if he continues to lose weight?

    Bookmark   August 13, 2006 at 11:46PM
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Hi Gibby. It is unlikely though not impossible for the test to be "wrong." The thyroid levels normally fluctuate throughout the day. Depending on where in the normal range your cat's T4 was, he could be slightly hyperthyroid but have been in a trough. One of my classmates has 2 cats that are hyperthyroid. One has a T4 of 3.8 or something like that, which is within normal limits (0.8-4.0), but she had all the classic symptoms. She repeated bloodwork and finally got a 4.2 and the cat improved on tapazole. Then she had the I131 done, and now her symptoms are completely gone. So your cat may be slightly hyperthyroid but very sensitive, and just happened to catch the T4 level in a trough. It wouldn't hurt to monitor a T4 every couple of months if he continues to lose weight. But if the level is closer to the middle or lower, then I'd worry about something else.

    Bookmark   August 16, 2006 at 7:30PM
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Has anyone had this issue? I've been giving my cat transdermal methimazole, a gel on the inner pinnae of the ear. She seems to be responding well to the medication, gaining weight, calmed down, but her ears are red now. I've been switching ears but now they are both red. I'm stopping by the vet tonight to ask him about it, but was wondering if anyone had seen this happen to their cat. I'm also wondering now, could it be an allergy to the latex gloves I use to rub this gel on her ear. Any similar incidents out there??

    Bookmark   December 28, 2006 at 4:31PM
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Dracana- I have heard that some cats are sensitive to the transdermal methimazole. I also know that some animals are allergic to latex. Non latex gloves are available. If you use them for a couple of weeks and it doesn't seem to help, then it must be the drug. Which would be a bummer. Perhaps there is something that the pharmacy could change in the transdermal prep to not cause that reaction, but I don't know. Since I work at a place that does the I131, we don't deal too often with cats on thyroid drugs. Most get the treatment.

    Bookmark   December 29, 2006 at 10:59AM
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Hi guys I'm sorry I don't know how to post right yet but I have a hyperthroid cat named paige who just turned 11. She has been on tapazole for 2 years and for the first time had a low t4 test. What do I do Lower meds?

    Bookmark   March 13, 2014 at 2:44PM
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When you posted a similar question on another pet forum, you said that she had *another* t4 test that was low. So I'm a little confused. Has she had a low t4 test more than once, and if so, when was the other low t4 test?

When was the last time you had her T4 checked (before this current check), and what was that test result? What tapazole dose was she on and for how long before that test?

What dose of tapazole is she on now, and how long has she been on her current dose before this most recent low t4 test?


    Bookmark   March 14, 2014 at 12:30PM
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