Hyperthyroidism in elderly cat. Should I push for Radioactive-Iodine Therapy? - Cat Forum : Cat Discussion Forums
 
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post #1 of 5 (permalink) Old 09-18-2015, 02:28 PM Thread Starter
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Hyperthyroidism in elderly cat. Should I push for Radioactive-Iodine Therapy?

Hi guys,

During my most recent vet visit with my 17-year-old girl Wintressia, the vet diagnosed her with hyperthyroidism.

My cat already has kidney failure (CRF/CKD) and IBS, both diagnosed several years ago. A year ago, my cat was also diagnosed with hypertension and was put on amlodipine, but during last month's checkup my vet said her blood pressure was normal, so apparently my cat has been "cured" of her hypertension.

Anyway, my vet started Win immediately on methimazole. When I got home from the appointment, I started doing research on hyperthyroidism in cats. I read that Radioactive-Iodine Therapy (I-131) is a (more or less) permanent cure, whereas taking medication is not. There can also be a lot of adverse effects from medication, plus with my cat's pre-existing kidney issues, methimazole can often cause even more issues.

I called my vet and brought up the potential of radioactive-iodine treatment. She seemed strongly against it and wanted me to try several weeks of methimazole, and then more bloodwork. I'm taking my cat in next Friday for her next bloodwork panel; she's been on the methimazole for ~2 weeks.

I know my cat is 17. I know she has kidney issues. I know I-131 treatment is expensive. I know she would have to stay in the vet hospital for 3+ days after I-131 treatment. I know it is dangerous to put an elderly cat under anesthesia.

I know my cat's age and condition make her an unlikely candidate for I-131 treatment, but, after doing research on hyperthyroidism in cats and the pros and cons of each course of treatment, I would still prefer to have the I-131 procedure performed on my cat, rather than keep her on medication for the rest of her life, medication that can never CURE her thyroid tumor, which will continue to grow.

Has anyone had any experiences with I-131 treatment in elderly cats, or cats with kidney failure? Am I still within my "rights" to insist to my vet that I want to pursue the I-131 treatment?

I can upload my cat's bloodwork/urinalysis from two weeks ago, but I noticed it doesn't actually list the T4 value, grr!


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post #2 of 5 (permalink) Old 09-18-2015, 06:33 PM
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My old cat also was hyperthyroid, but she had an inoperable bladder tumor and was going to go out relatively soon so we did nothing at all about it.

My experience with radioactive iodine is personal - *I* had it done for hyperthyroid. And it made me *hypo*thyroid. Now I take thyroid meds every day - for the rest of my life. Would this be acceptable to you for your cat? From everything I know, radioactive iodine treatment is fairly inaccurate, best-guess, hit-or-miss, and my situation (going hypo) is very common. Do the reports indicate it is radically different with cats, that they can pinpoint the correct dose? Personally I'd think twice for an elderly cat who already has health issues.
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post #3 of 5 (permalink) Old 09-18-2015, 07:06 PM Thread Starter
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Oh wow, thank you Eldercat, I read that a cat's hyperthyroidism paralleled that in humans, but it's amazing to hear from someone who actually personally did the radioactive-iodine route.

Hypothyroidism is definitely listed as a risk of radioactive-iodine treatment in cats, but it seems like most vets list it as a very small % risk.

Feline Hyperthyroidism by Lisa A. Pierson, DVM
Dr. Pierson lists the risk of hypoT at ~5%, and the "failure rate" (i.e., cat remains hyperT) at ~5%.

Animal Endocrine Clinic: Success Rates for Radioiodine Treatment in Hyperthyroid Cats
Dr. Peterson also lists a "failure" rate of 5%.

Those seem like pretty acceptable percentages to me, and I also consider that even if my cat fell into one of the ~5% categories, she'd be taking daily medications (either remaining on the methimazole, or taking a thyroid supplement as you are) - but if I never tried the treatment at all, she'd be on daily medications anyway.

Her "quality of life" is otherwise very high right now - she is still a very active, VERY happy cat. She plays with toys, runs around, purrs a lot, and has a great appetite. She doesn't show any of the classic "symptoms" of hyperthyroidism in cats, but I don't want to let things go on without doing anything, either :/


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post #4 of 5 (permalink) Old 09-18-2015, 07:29 PM
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One thing they tried with *me* before RI treatment was the methimazole (also tried propylthyouracil). Sometimes a person will go into remission or it will somehow kickstart the system back to normal. It is possible to play with this several times before deciding that hyperthyroidism is permanent. You might want to give the pills a good run first - the expense is massively different and the side effects , well who knows. RI is radioactive after all. And the anesthetic is a risk too. Of course I had none, just drank the thing down and then drank water the rest of the day - thought I'd swell up and pop from all that liquid!

Good appetite, slim, active, and sometimes high blood pressure can come with hyper in people. Also skin and hair changes and eye changes. Depends on what type of hyper.
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post #5 of 5 (permalink) Old 09-18-2015, 09:42 PM
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Maggie was 15 when she was diagnosed with Hyper-T. We first used methimazole to stabilize her and reach euthyroid. At that point her blood tests showed that her kidneys were in pretty good shape for a cat her age, all of her other values were normal as well so I went ahead and did I131.

The vet told me that the risk of going hypothyroid was small. She also said she'd rather deal with a hypo cat than hyper. The medication doesn't have as many side effects and the dose is smaller and more palatable. She also felt that hypo was much easier to manage as the condition remained stable rather than hyper where you need to regularly adjust dosage.

She was at the facility for 3 days and for two more weeks I had to minimize contact with her. No sitting or sleeping near me, so I had to put her in the spare bedroom at night because she normally curled up against my belly. She was not anesthetized, the treatment was an injection that they said is no worse than a vaccine. With all of the pre and post blood work and x-rays, plus the procedure and boarding...I can't remember exactly but it was somewhere between $1500-2000. I think closer to $2K. That was 3.5 years ago.

Maggie did develop a fairly rare side effect a couple months after the treatment...she started losing fur in clumps, kind of like a Husky shedding in spring. It also turned a reddish color, looked like what is called rusting in black cats. It took a month or two for the shedding to stop, but the color never went back to normal.

If I were you, I'd have her achieve euthyroid on methimazole and then assess her other conditions. Hyper-T often improves kidney function, so correcting the Hyper-T may show that the kidneys are really in worse condition than they currently seem to be. Once you have that information a consultation with the I131 facility can help you determine if doing it would be a good choice.


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Last edited by doodlebug; 09-18-2015 at 09:44 PM.
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