Cat bloodwork Q

I have an adult cat that’s hyperthyroid and managed on methimazole. He’s been stable and I’d like to radioablate so asked my vet to run some bloodwork to start that process.

It shows some out of range values related to his red cells:

The vet is unconcerned because hemoglobin is normal, but I look at this and see a long standing dyscrasia that’s trending up/down. I’ve reached out to another vet I work with to discuss, but do the vets here have any feedback (@Ghazzu ?) I’ve lost a couple pets unexpectedly in the past year and don’t want to miss something here :frowning:

My guess would be that it is secondary to the underlying hyperthyroidism.

Oh, wow, okay. Thank you, that worries me less. Here’s the T4 & history. Overall he seems to be doing well on this front & has regained the weight that he lost prior to dx.

If we ablate with radioactive iodine, should that address the red cell issue, too? Is there anything I need to look at more closely before considering that? His kidney values are solid although his SDMA has come up to 13 from 10 last year.

I would think it would.
FWIW, I had I-131 tx some years back on one of my cats (when it was still relatively new) and I would definitely go that route again.

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Wonderful, thank you, I really appreciate your input. I’m very hopeful about the radioactive iodine, especially for this guy. He’s not a real fan of leaving the property or of other people, the vet’s suggestion of surgery seemed tough for him. An injection seems kinder.

Microcytosis (small red cells as indicated by the low MCV) is not uncommon in cats with hyperthyroidism. In many cats it resolves with radioiodine treatment.

The good news in you cats case is he is not anemic, He has been able to adapt by making more red cells.

Here’s an article.

Incidence of microcytosis in hyperthyroid cats referred for radioiodine treatment - PubMed (


Fantastic, I love it, thank you! This level of detail is so helpful. It’s really interesting that they don’t know why this happens, even in people.

The vet mentioned the possibility of iatrogenic hypothyroidism in passing, also touched upon here. I didn’t realize it was SUCH risk–40% of treated cats developed it here, this one says 20-50%, wow.

It looks like further bloodwork to look at tsh after methimazole has been discontinued, scintigraphy to evaluate the thyroid, and personalized dosing is all important to minimizing that risk? Can I expect to find that sort of care only at a university teaching hospital or is it likely my local referral hospitals are approaching it with these things in mind? (I’m in CT.) While having hyperthyroidism persist would kinda suck after spending the $$, that seems a lot less scary than just burning out the thyroid.

Good wishes to you and your kitty. I have nothing but positive things to say about radioactive iodine treatment for thyroid disease in cats. It’s a goddamn miracle, or as close thereto as it gets.

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Surgery is pretty behind current standard of care at this point, with higher risk of complication. I-131 is a really great option for a cat like yours.

The last time I remember a surgery on one (as the nurse/anesthetist not the surgeon) was a long time loyal client with serious financial concerns who wasn’t going to be able to medicate and monitor as needed. My boss was willing to do it for cheap and figured it was the only shot the cat had. She did well but it definitely isn’t first choice these days!


Thank you @vxf111! I’m glad to hear you had a positive experience! I think we live in roughly the same area of the county…can I ask who you used for your kitty? Did you do scintigraphy before ablation?

Thank you too, @volvo_240! I see this vet because he’s generally very pragmatic, has a lot of experience, and is nearby. I do appreciate his viewpoint, but think iodine therapy is definitely a better choice for this cat.

I am worried about overshooting & burning out his thyroid, and also about just managing him through this. He’s my barn cat and usually doesn’t wander (and is locked in the tack room at night) but I’m not sure how he’ll feel when we d/c the methimazole, or how upset he’ll be as an inpatient, or how he’ll be when we bring him home. That’s a lot for a cat that’s very wary about people he doesn’t know & isn’t used to being confined or “inside.” :frowning: I can’t bring him in and let him have the run of the house due to other cats, but I may bring him in and give him a cat tower through this. Will just have to play it by ear.

I used RadioCat at Blue Pearl Hospital in Delaware. I cannot speak highly enough about the staff and the procedure. They did not recommend scintigraphy in advance. The bloodwork was very indicative of the problem being the thyroid and (at the time) he did not have any other major underlying issues-- so it was pretty clearly an appropriate treatment.

My cat was a housecat, but honestly the reason they want you to segregate the car post procedure is because his waste is radioactive, not because he’s going to feel bad/different. Crosby was exactly 100% his usual self immediately following the procedure (they sent me a video of him waking up and yowling for food and attention). I think you could close your cat in the tack room or similar and just warn people not to touch the litterbox.

I don’t think the procedure is too invasive on them. Putting in the IV is the worst part. After that it just sort of happens and they don’t really particularly know a procedure is happening. I’ve had nearly feral barn cats go through much more invasive procedures than radioactive iodine treatment. Just warn them he’s not a pet cat. They’ll know what to do.

And if you can’t contain him, just watch out for his waste and take it away and put it in the trash if you find it. I mean, it’s not IDEAL for him to spread biowaste all over creation but if he’s slinking off to poop in a hole in the woods, what are the odds that anything is going to come in contact with the waste?

Thank you, that’s great to know you had such a good experience at RadioCat. I’ve heard them mentioned a few times. From what I understand, scintigraphy is about personalizing the radiation dose to limit the chance of iatrogenic hypothyroidism or persistent hyperthyroidism post treatment. Here’s a write up about it:

I think maybe I’ll see about using that clinic.

My fear pre treatment is that rising thyroid hormones will make him feel anxious or poorly enough to run off (which would be very unusual for him, he’s a home body, but I don’t know how he’ll feel once his thyroid is over producing again), and then post treatment he’ll be so freaked out by the experience that there’s the same risk. He’s a very sweet cat and has never been difficult at the vet but it definitely stresses him a lot to go somewhere new & meet new people. For example, when he goes to the vet, I lock him in the tack room when we get home instead of just letting him loose, so he can chill and remember he’s home and safe. But days away is different than a 20 minute visit.

I do always worry when pets have to go be hospitalized for something, but there’s just this extra level when it’s a cat that’s really particular about his place and people, and the only thing keeping him around is his desire to be here. I’m generally not a fan of outside cats and everyone else is strictly indoor only, but we trapped this guy as a starving adult stray. Not only has he clearly always been outside, but he’s really good at his job and happy with his life.

Did you see a change in your cat for that week or two after you stopped methimazole? I’m not sure what to expect.

The three days Snickers was off methimazole she was vocal, lethargic and didn’t eat well. I expected it to be like before she was diagnosed with hunger but no.

She’s not a happy camper traveling, didn’t eat well when she was there but once home, was back to normal the next day. My vet gave me gabapentin for her while traveling.

I had to give her thyroid meds for the first month after the I-131 but after that and to this day, her thyroid levels are perfect.

She had it 1 1/2 yrs ago and I would definitely do it again. Shes gained back all the weight she lost and doesn’t look 17.

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My cat was not on any meds for thyroid disease pre Radiocat. The very minute he was diagnosed I said “let’s do this” and booked the radioactive iodine treatment. I was already familiar with it from human use (not me personally) and didn’t want to try medication first. I just wanted to nuke the darn thyroid :wink:

They didn’t mention any further diagnostics to me. I would have done them if recommended but they weren’t.

It’s tough when you have a sensitive cat. I feel you on that. Crosby was never a shy violet :wink:


Perhaps they can keep him on a low dose of gabapentin while he is hospitalized, and have on hand at home if he’s struggling staying indoors.