cat with hyperthyroid

gibby2015August 24, 2009


I first posted here when my 19 year old cat passed on due to CRF. I have a 15 year old cat with IBD - who now has hyper-t. He's been treated with medication for 5-6 weeks now and is doing much better. Just curious if anyone here is dealing with hyper-t with their cat. I've been to the yahoo forum and will continue to use that but sometimes the yahoo forums on pet illnesses are just not quite the right fit for me.

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My cat Basil became hyperthyroid at age 8, quite young. He's had radiation therapy twice. Before the therapy, both times he declined really rapidly--weight loss, yowling, extreme hyper activity--and after the therapy just as rapidly returned to fit and healthy. He's ten now,in perfect health, and the last radiation was in January. I am hoping and praying that one was the cure.

    Bookmark   August 24, 2009 at 6:08AM
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I have two hyperT cats. One is also CRF and hyperPTH. Both are currently euthyroid on carbimazole (both experienced digestive upset on methimazole, which is why I switched them to carbimazole). Tommy is a candidate for I-131, but the expense and the fact that the nearest I-131 clinic is 200+ miles away will prevent me from pursuing that option for her. Billy isn't a candidate for I-131 because of his other health issues.


    Bookmark   August 24, 2009 at 9:23AM
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My late Pumpkin developed Hyper-T when she was ~11 years old. I opted for the medication, Tapizole (I think generics are now available)because of the expense of Radioactive Iodine. (Incidently, I had RI treatment for my own hyperthyroid but my health insurance covered it.) She lived for another relatively healthy 2 years, although the treatment did involve going for periodic blood tests and some adjustments on the dosage.

If she was younger, I might have gone for the RI.

    Bookmark   August 24, 2009 at 9:41AM
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Thanks for sharing! I will likely continue with the medication rather than I-131 since he's older and he's a good pill taker. Methimazole is the generic name for Tapizole. For those who have taken the medication route, how often did you return to the vet for periodic blood tests? If you had problems with methimazole, how long did it take for that to show up? Boris has so much digestive upset from the IBD and had even more before starting this medication - he's in much better shape in that respect now.

    Bookmark   August 24, 2009 at 10:11AM
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Hi Gibby,

My Muddy Buddy is 15 and has been hyper-t for the past 3.5 years. She is also on methamizole (she's also CRF, but doing fabulously on that end of things).

She's never had any problems or side effects with the methamizole. We didn't consider I-131 because she's older, isn't in great health, and is a good pill taker. She's needed her medication adjust often over the 3.5 years. Sometimes she's taken as little as 2.5 mg/day and sometimes she's taken as much as 10mg/day. The vet has nicknamed her "yo-yo cat."

We've generally taken her ever 3 months for whatever bloodwork is needed- sometimes it's only thyroid, sometimes other things. Since last October she has done very well and not needed any adjustments to medication, so the last time she went they let us off the hook for 6 months, as long as she is doing well. During the initial treatment, we did go once a month for 3 months until the vet was confident we were in the right range of medication for the moment.

Good luck to your and your kitty.

    Bookmark   August 24, 2009 at 11:55AM
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Billy and Tommy both showed signs of digestive upset pretty much as soon as they started taking methimazole. In Billy's case, his CRF was already causing inappetance, so the only indication that methimazole might be exacerbating the stomach upset was increased lip licking on his part. That's why I switched him to carbimazole, which is supposed to cause less digestive upset than methimazole. I figured there was no value in making him feel even oogier with methimazole.

Tommy, too, showed signs of nausea right after starting methimazole, so I switched her to carbimazole after just a few doses of methimazole.

In both cases, I took the "start low and go slow" approach to dosing to avoid potential kidney crashes and hypoT. They started on a very low dose of the drug and retested in 3 weeks. Med was adjusted slightly if indicated by bloodwork with another retest in 3 more weeks. And so it went with a small med adjustment followed by a retest in 3 weeks until each cat safely achieved euthyroid. Now that both cats are euthyroid, I will be retesting Tommy every 6 mos unless her behavior suggests the need earlier. Billy will be retested more often because of his other medical issues.

Gibby, how long after starting methimazole did you have Boris retested? If you haven't had him retested yet, you should do so right away. Make sure that the retest does/did include a check of his kidney values, since uncontrolled hyperT can mask renal failure. You need to know what, if any, impact the methimazole has had on his T4 and on his kidney values in order to find the best med dose for him.

I assume that your vet explained the long-term risks of methimazole. It is a very strong drug that has the potential to do significant damage over time. For this reason, I-131 is a safer treatment option for cats with healthy kidneys. Besides which, methimazole just manages the symptoms. It does not cure the disease. I-131 is a CURE in more than 99% of cats who undergo the treatment.


    Bookmark   August 24, 2009 at 2:24PM
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Laurie - he was tested after 4 weeks on the methimazole - his kidney function is normal and his liver values are dropping close to normal as well. His T4 has dropped from around 12 to 1.4. For now I'm okay with the meds - not really looking to send him off for ten days for the I-131. He's had quite a few health issues over the last few years - including three eye surgeries plus dealing with the IBD. And I don't know what impact it has on a cat to lose one of their housemates. But right now he's doing quite well and seems to be enjoying life so I'm probably not going to disrupt that any more than absolutely necessary.

    Bookmark   August 25, 2009 at 12:22AM
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It sounds like methimazole is doing its job for Boris. That's quite a drop in T4. What is the lab's reference range? Is 1.4 in the reference range? If so, is it low normal, mid normal, or high normal? Ideally with an aged cat with healthy kidneys, you want to maintain the T4 in the low end of normal range.

    Bookmark   August 25, 2009 at 2:27AM
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I don't have the results with me but yes it's in range and it's low normal - right where he should be according to the vet. I think I actually do have a decent vet. I switched to him when my other cat was diagnosed with CRF - referred to him by my pet sitter via one of her very particular clients who also had a CRF cat. He is very thorough and much more comprehensive in terms of follow up than my old vet who was not too good for anything other than routine vaccinations.

    Bookmark   August 25, 2009 at 10:26AM
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