Radioactive Iodine treatment for hyperthyroid cats - experience?

[Alex_and_Bodie_s_Mom]

Just as the title says - looking for experiences with treating hyperthyroid cats with radioactive iodine. My OG, Mick, is 19 or 20 years old, and doesn’t tolerate either the pills or the transdermal gel for her hyperthyroidism (won’t eat the pills, won’t take the pills, won’t let me get near her with the gel).

Her levels are quite high again, and I’m wondering if we should go ahead and do the iodine therapy. Not sure about the cost, or the logistics of it (I think the nearest place to me that would do it is OSU, about 1.5 hours away), and of course, very worried about doing it at her age.

But other than being pretty darn skinny right now, she’s in really good health for her age, very active, bright. Just ran bloodwork today and she’s totally normal (even kidneys!) except for the thyroid levels. Am I crazy to consider the iodine treatment? How long does it take to get results?

[OzarksRider]

I’ve had two hyperthyroid cats that had the radioactive iodine treatment. Both were cured. It took about 10 days from the day they were injected to see results, and it was like magic. And for what it’s worth, I take thyroid medication and if I have to reduce my dose it takes about 10 days and then I suddenly feel like all is right with the world again. It’s probably a similar experience for cats.

As for the procedure . . . I took my cats to the clinic on a Monday, they were injected that day, and I picked them up on Friday or Saturday (4 -5 days in the hospital). They were isolated while they were hospitalized because they were radioactive. Radioactivity was measured every day, and when it was low enough they were discharged. Once they were home I kept them confined in the house for a couple of weeks (can’t remember if it was 2 or 3 weeks) and I bagged the litter and stored it for about 3 months until the radioactivity had enough time to decrease so that I could dispose of it. About a month after the treatment I took them back to my regular vet to have their T4 checked. One cat was completely normal, the other had a slightly decreased T4 which resolved over about 6 months without any other treatment.

You’ll have to ask the clinic where your cat will be treated about their specific protocols. Will the cat have to be taken off thyroid medication before the treatment, and if so, for how long? Be sure they know how severe your cat’s symptoms are, because they may shorten the time she has to be without her medication. Also ask about any testing they require either from your vet or when she arrives at the clinic. Some facilities do thyroid scans to help customize the dose of radioactive iodine.

My last hyperthyroid cat was treated 5 years ago, and the cost then was $1200, but the clinic I used did not do thyroid scans. If I had gone to the vet school it would have been more, around $2000, I think.

Old age alone does not contraindicate radioactive iodine therapy as long as your cat is otherwise healthy. You’ll just have to weigh the pros (cured of the disease, no more pills) and cons (cost, short term inconvenience, continued progression of the disease) and decide what’s best for you and your cat.

[Simkie]

I did radioactive iodine for my barn cat a little more than six months ago. It was an excellent experience and I wouldn’t hesitate to go that route again should the need arise.

I went with a clinic that does scintigraphy and a personalized dose of radiation, which lowers the risk of iatrogenic hypothyroidism or persistent hyperthyroidism following treatment. Risk of “missing” the target can be quite high otherwise.

[Alex_and_Bodie_s_Mom]

Thanks to both of you - exactly the info I was looking for.

The vet is going to look into nearby clinics (probably OSU) that might offer this treatment, because he’s never referred anyone for this before. It doesn’t seem to be a very common idea in our area, so it could be that no one nearby does it. I could take half a day off to take her to OSU, but taking her to K-State would be an entire day for me.

Meanwhile, we’re going to try to compound her meds into a liquid, rather than the pill. Maybe that will make her more likely to take it.

[LLJet]

Have you considered Hill’s Prescription Diet y/d? We’ve used it for people in the same boat as you who can’t consider iodine treatment due to anesthetic risk or cost.

[Alex_and_Bodie_s_Mom]

I didn’t even know about that - I don’t think my vet carries that specific one, so it would probably be a special prescription he’d have to order, or I’d have to get from Chewy or somewhere. With X number of cats in the house, though (let’s not talk about how many!), feeding one a specific diet is challenging!

[OzarksRider]

Two private practices in Tulsa offer radioactive iodine therapy: http://www.felinespecialties.com/radioactive-iodine-treatment.asp and https://vcahospitals.com/woodland-east/services/advanced-care/feline-hyperthyroidism.

For my cats, the worst part of the process was that they had to be off methimazole for 2 weeks before their appointments. It was especially bad for one cat that had severe symptoms–her T4 was so high the machine couldn’t read it. Since then, I have read that the period without medication can be shortened for cats with severe symptoms. Be sure to ask about this if you think it might apply to your cat.

When my first cat was diagnosed with hyperthyroidism the vet didn’t even mention radioactive iodine treatment as an option. I had to do all the research myself and then tell him to refer me to the clinic, which thankfully he didn’t argue about. After the treatment, when I took my cat back to my regular vet for followup testing, the T4 was a little low and the vet wanted to put her on thyroid replacement therapy. I called the clinic that had administered the radioactive iodine and asked them what to do. They said don’t treat the hypothyroidism just yet; give it a little more time. Sure enough, her thyroid function recovered and was normal within 6 months. So if your vet is not familiar with cats that have had this treatment be sure to ask him to consult with the clinic if something unusual occurs after treatment.

I get what you mean about finding a treatment facility within a reasonable distance. I had 2 options, one in Memphis and one in Columbia. Both are about a 4 hour drive for me. It was not fun.

[Simkie]

I found this paper really helpful in understanding what to ask and what to look for when comparing radioiodine clinics:

Predicting outcomes in hyperthyroid cats treated with radioiodine

Here’s another that reviews the various treatment options:

https://www.sciencedirect.com/science/article/abs/pii/S0195561620300516

Peterson was the guy who “invented” treating hyperthyroid cats with radioactive iodine, and he’s still very active in clinical practice and research–he’s published loads about hyperthyroid cats, and I found it all really interesting.

[mbv]

I had my cat treated at a vet school and had a positive experience even though she ended up being a “5 percenter” that remained hyperthyroid after treatment. She now requires a much lower dose of methimazole. She was eligible for another round of I131 but I declined that and went for medical management instead due to costs (about 1600 in 2022). My cat is fractious at the vet so I was a little worried about leaving her there for a week (drop off Thurs or Friday with scintigraphy and planning, treatment on Monday and then pick up on Friday), but they really don’t handle them much at all once radioactive so it was not an issue. Aftercare wasn’t too bad as I had space to store the litter and supplies. I ended up using some inexpensive duplicate supplies that I threw away at the end of her isolation.

One thing to consider is that radiation laws vary across states, which can affect how long your cat has to stay at the clinic, how long you need to wait to dispose of litter after treatment, and also can affect the dose of I131 that can be administered. If your cat has very high T4 and may need a high dose this may affect dosing. My cat had the max dose allowed in my state, but this was lower than is allowed in some other states. Sometimes I wonder if she had a higher dose if she would have become euthyroid.