Radioactive Iodine therapy to treat hyperthyroidism

maurice12

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Hi everyone,

We are now dealing with a health issue (biggest one he's ever had) for our 13 year old male cat. He was diagnosed with hyperthyroidism and the vet put him on methamazole for a month. He has his vet appointment next week to check his levels again and then he's supposed to be scheduled in for his radioactive iodine therapy a week after that. I already made the appointment at the cat specialist and got funds together in preparation. However, my biggest concern, is the 3-5 days he has to spend at the place after the treatment. He is very skittish, afraid of pretty much everyone but me and sometimes my girlfriend. He hates going to the vet and in the past he's given me days of food strikes when he went through something that was too traumatizing (moving, a vet visit, too many people in the house for hours, etc). I am really afraid that these 3-5 days away from his family are going to be incredibly hard on both of us and I'm worried about his recovery. I'm also really scared that he won't eat anything for the entire 3-5 days that he's away and I'm not sure if the nurses are going to try as persistently as I do when he refuses food. He also tends to not use the bathroom when he's upset like this which is especially dangerous since he also has FLUTD and it will likely flare up while he's in a high stress situation, not eating or drinking and holding it all in. I'm not even thinking about how long it will take me to get him to eat again once he comes back home but that is another big issue that I will have to figure a way around later. I'm posting here because I wanted to see if anyone might have any advice on how you handled it with your skittish cat. Is there anyway I can make this easier for him when the time comes? Anything I can do to help him get used to this very scary situation that he's going to be stuck in for 3-5 days? I don't want him to think I abandoned him forever but I know the stress and depression of that is going to keep him from eating/drinking as well.
 

molly92

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I would strongly recommend discussing scintigraphy with the radioiodine clinic beforehand! Scintigraphy measures the size of the tumor very accurately and a vet can calculate an individual dosage of radioiodine based on the tumor's size. One size fits all dosing is typically 4 millicuries, which is standard because excess usually just gets excreted, but doing the extra work of estimating a more precise dose is a bit safer, and, most of the time, cats need much less than 4 millicuries. The reason I recommend this for you is because the less radioiodine is injected, the faster the radiation levels fall and the sooner the cat come home.

If I had a hyperthyroid cat again, I would shop around for a clinic that definitely does scintigraphy based dosing, even if it was a little less convenient or I had to wait a little longer for an appointment. It's just a much more precise way to do the treatment, and it is recommended by the most qualified veterinary hyperthyroidism specialist in the US, Dr. Mark Peterson.

I did have a cat undergo radioiodine therapy at a clinic that did not do individual dosing. They didn't have scintigraphy experience, but I did ask them to lower the dose, because studies have shown that even just 2 millicuries is effective for the majority of cats. They didn't want to go as low as 2 (although I do think it would have been fine because my cat was so tiny and her tumor wasn't even palpable), but they compromised with me and gave her 3 millicuries instead of 4. She was given the procedure on a Monday, they didn't even test her radiation levels on Tuesday, but on Wednesday they did and she was well below the state requirements. They were very surprised, but that's because they always give cats 4 millicuries and they gave her less. I wonder if she would have been ready to come home even sooner if they checked her sooner!

I'm not saying that will be your cat's experience, and every state has different regulations on what level of radioactivity is allowable before going home. But, tailoring the dose more precisely through scintigraphy increases the chances that your cat will be able to come home sooner. (There are other methods for estimating dosage, but they're not as accurate and most places that bother with individual doses it all will do it with scintigraphy).

I also think you need to talk with the vet beforehand and go through his issues THOROUGHLY. Staying hydrated will be really important for obvious reasons, but also because urine is how most radioiodine leaves the body. They should convince you that they have a plan in place to keep your cat hydrated at the very least. Subcutaneous fluids might be an option. If you're not confident after talking to them that they're going to closely monitor your cat and keep him as healthy as possible, find a different vet. Ask your regular vet if there are any safe tranquilizers or anxiety medications that can be given to him the day of and/or during his stay, and also for the drive there and back if it's far.

It sounds like he will be stressed by the experience regardless, but hopefully the vet(s) will work with you to make the process as smooth as possible. Have you ever tried any Feliway products with him? If not, they may help with his stress and anxiety, especially when he comes home.

Also get clear information from your vet what is expected after the procedure and when to be concerned. He will probably eat less regardless of stress after the treatment, so how long can he go without food or water before you need to contact the vet? Get all of those questions figured out beforehand, so that you yourself will know what to expect and can relax a little bit. I'm sure you're very stressed on his behalf when he doesn't eat, but remember, he's also picking up on your emotional cues, so do what you need to do to help yourself feel as calm and prepared as possible.

If at any point you feel like you're getting pushed aside by a vet or vet staff, be persistent and be annoying! Remember, you are your cat's advocate! I'm sure the vet I went to complained about me after I left for being difficult (I printed out a stack of scientific papers and had them go through them with me), but I'm glad I was difficult and got that dose lowered. If I were to do it again, I'd be even more difficult.

One other thing you might want to check up on, often the cat needs to be off of methimazole for a couple of weeks before radioiodine treatment. I'm not sure if you were made aware of that or not, but be sure to get that confirmed in advance.
 

molly92

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Oh, and I would like to add: the radioiodine experience might be stressful but it is absolutely worth it! The best thing about hyperthyroidism is that, unlike so many other cat diseases, it can be completely cured. It was such a relief the day I brought my cat home and I couldn't hear her heart beating out of her chest anymore and she was just much calmer and relaxed. It takes a few months for things to really stabilize, but there are usually some instantly noticeable differences and it's very gratifying to have been able to fix something like that for your cat so effectively and so quickly.
 

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I had my cat treated two years ago and I was worried because she was a really shy and fearful cat, so I didn't know what to expect for the 4 days she had to stay in isolation, far from home, with people she didn't know at all.

From my experience, the staff at the facility won't try to convince the cat to eat if he doesn't want to. The staff has very little interaction with cats, because they are radioactive, and the staff needs to limit the exposure to the radiations.
My cat lost at least a pound during the isolation, though they told me she was eating a lot. I took her food with her, in order not to upset her further, and because she had to eat a specific food. She would eat a can a day, when she was home. I gave the staff a 24-can pack when I took my cat to the facility, they returned me 11 cans. I don't believe she ate 13 cans in just 4 days. I think they offered her the food in the dish in the morning and afternoon. She ate very little at each meal, they would throw the remainder away.

The only thing you can do is to let the staff know of this aspect of your cat's behavior, so that they can have some extra attention, but I don't think they can do more than this.

For the rest, do follow the advise molly92 molly92 gave to you. I had my cat scanned with a scintigraphy at the same facility where she received the I-131 shot. My cat received 1.2 mCu of radiation based on the size of her thyroid tumor.
 

fionasmom

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Fiona herself was hyperthyridic and was dxed at about 13 and lived to 16. She took Felimazole; however, if I had to do this again I would definitely look into the radioactive iodine therapy. Her vet at the time made no moves in that direction and I was not well informed about it.

I completely agree that you need the best care that you can get with all the bells and whistles. When my pets, (dog especially has been a medical nightmare) need specific care I always find a specialist and there is a difference in the general management of the animal.
 
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maurice12

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I would strongly recommend discussing scintigraphy with the radioiodine clinic beforehand! Scintigraphy measures the size of the tumor very accurately and a vet can calculate an individual dosage of radioiodine based on the tumor's size. One size fits all dosing is typically 4 millicuries, which is standard because excess usually just gets excreted, but doing the extra work of estimating a more precise dose is a bit safer, and, most of the time, cats need much less than 4 millicuries. The reason I recommend this for you is because the less radioiodine is injected, the faster the radiation levels fall and the sooner the cat come home.

If I had a hyperthyroid cat again, I would shop around for a clinic that definitely does scintigraphy based dosing, even if it was a little less convenient or I had to wait a little longer for an appointment. It's just a much more precise way to do the treatment, and it is recommended by the most qualified veterinary hyperthyroidism specialist in the US, Dr. Mark Peterson.

I did have a cat undergo radioiodine therapy at a clinic that did not do individual dosing. They didn't have scintigraphy experience, but I did ask them to lower the dose, because studies have shown that even just 2 millicuries is effective for the majority of cats. They didn't want to go as low as 2 (although I do think it would have been fine because my cat was so tiny and her tumor wasn't even palpable), but they compromised with me and gave her 3 millicuries instead of 4. She was given the procedure on a Monday, they didn't even test her radiation levels on Tuesday, but on Wednesday they did and she was well below the state requirements. They were very surprised, but that's because they always give cats 4 millicuries and they gave her less. I wonder if she would have been ready to come home even sooner if they checked her sooner!

I'm not saying that will be your cat's experience, and every state has different regulations on what level of radioactivity is allowable before going home. But, tailoring the dose more precisely through scintigraphy increases the chances that your cat will be able to come home sooner. (There are other methods for estimating dosage, but they're not as accurate and most places that bother with individual doses it all will do it with scintigraphy).

I also think you need to talk with the vet beforehand and go through his issues THOROUGHLY. Staying hydrated will be really important for obvious reasons, but also because urine is how most radioiodine leaves the body. They should convince you that they have a plan in place to keep your cat hydrated at the very least. Subcutaneous fluids might be an option. If you're not confident after talking to them that they're going to closely monitor your cat and keep him as healthy as possible, find a different vet. Ask your regular vet if there are any safe tranquilizers or anxiety medications that can be given to him the day of and/or during his stay, and also for the drive there and back if it's far.

It sounds like he will be stressed by the experience regardless, but hopefully the vet(s) will work with you to make the process as smooth as possible. Have you ever tried any Feliway products with him? If not, they may help with his stress and anxiety, especially when he comes home.

Also get clear information from your vet what is expected after the procedure and when to be concerned. He will probably eat less regardless of stress after the treatment, so how long can he go without food or water before you need to contact the vet? Get all of those questions figured out beforehand, so that you yourself will know what to expect and can relax a little bit. I'm sure you're very stressed on his behalf when he doesn't eat, but remember, he's also picking up on your emotional cues, so do what you need to do to help yourself feel as calm and prepared as possible.

If at any point you feel like you're getting pushed aside by a vet or vet staff, be persistent and be annoying! Remember, you are your cat's advocate! I'm sure the vet I went to complained about me after I left for being difficult (I printed out a stack of scientific papers and had them go through them with me), but I'm glad I was difficult and got that dose lowered. If I were to do it again, I'd be even more difficult.

One other thing you might want to check up on, often the cat needs to be off of methimazole for a couple of weeks before radioiodine treatment. I'm not sure if you were made aware of that or not, but be sure to get that confirmed in advance.

Thank you so much for this very detailed response. I will absolutely be discussing the scintigraphy with the vet since no one has even mentioned that to me at all. The vet suggested a few places but I just went with the one that they said was best. I didn’t realize that I could looking for other important services at the specialist.

This might be a big ask but do you by any chance have a link to any of those studies so I can get informed and make sure i have the research on hand that I can show to the vet. My other fear is just that if I am demanding towards the vet they’re going to take it out on my cat while he’s under their care. I know it’s unlikely but I have major trust issues when it comes to other people handling my cat.

I give my cat gabapentin to keep him calm during vet visits and any other chaos but I have to talk to the vet about that as well to ask if that’s the best option for his anxiety. You’re absolutely right about making sure this is thorough and I feel good about his health and safety before leaving him there because if they can’t promise that, I cannot trust them with him. He needs to stay hydrated throughout his stay

I have tried feliway products and I’ve definitely noticed some difference when I use the diffuser, not much with the collar but that’s just because he doesn’t usually wear a collar and just absolutely hated having something around his neck.

The vet that I have told me he only needs to be off methimazole for one week and then he should be all set for his appointment. I will confirm with them to make sure that’s correct.

I also absolutely think the radio iodine is worth it mainly from just seeing how low his energy level has been ever since I put him on methimazole, I couldn’t bear to see him live this way for the rest of his life. He is very kooky when he’s happy and I want my kooky cat back 😂
 
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maurice12

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I had my cat treated two years ago and I was worried because she was a really shy and fearful cat, so I didn't know what to expect for the 4 days she had to stay in isolation, far from home, with people she didn't know at all.

From my experience, the staff at the facility won't try to convince the cat to eat if he doesn't want to. The staff has very little interaction with cats, because they are radioactive, and the staff needs to limit the exposure to the radiations.
My cat lost at least a pound during the isolation, though they told me she was eating a lot. I took her food with her, in order not to upset her further, and because she had to eat a specific food. She would eat a can a day, when she was home. I gave the staff a 24-can pack when I took my cat to the facility, they returned me 11 cans. I don't believe she ate 13 cans in just 4 days. I think they offered her the food in the dish in the morning and afternoon. She ate very little at each meal, they would throw the remainder away.

The only thing you can do is to let the staff know of this aspect of your cat's behavior, so that they can have some extra attention, but I don't think they can do more than this.

For the rest, do follow the advise molly92 molly92 gave to you. I had my cat scanned with a scintigraphy at the same facility where she received the I-131 shot. My cat received 1.2 mCu of radiation based on the size of her thyroid tumor.
Wow that is terrible. I read the part on our cat specialist’s website about the staff only having limited interaction with the cats (which is reasonable) but it definitely made my heart drop. It‘s ridiculous that they basically stole your cat food even after you paid 100s of dollars for the treatment.

I truly hope he doesn’t lose any weight. He’s currently about 8 lbs and I worked hard to get him to that because he was losing weight last year. He’s really tiny, he was the runt of his litter.
 
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maurice12

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Fiona herself was hyperthyridic and was dxed at about 13 and lived to 16. She took Felimazole; however, if I had to do this again I would definitely look into the radioactive iodine therapy. Her vet at the time made no moves in that direction and I was not well informed about it.

I completely agree that you need the best care that you can get with all the bells and whistles. When my pets, (dog especially has been a medical nightmare) need specific care I always find a specialist and there is a difference in the general management of the animal.
the vet that we took him to doesn’t do I-131 shot so we started out with a cat specialist. Based on these comments I might have to switch to a different cat specialist to make sure he’s given the best care possible.
 

molly92

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Thank you so much for this very detailed response. I will absolutely be discussing the scintigraphy with the vet since no one has even mentioned that to me at all. The vet suggested a few places but I just went with the one that they said was best. I didn’t realize that I could looking for other important services at the specialist.

This might be a big ask but do you by any chance have a link to any of those studies so I can get informed and make sure i have the research on hand that I can show to the vet. My other fear is just that if I am demanding towards the vet they’re going to take it out on my cat while he’s under their care. I know it’s unlikely but I have major trust issues when it comes to other people handling my cat.

I give my cat gabapentin to keep him calm during vet visits and any other chaos but I have to talk to the vet about that as well to ask if that’s the best option for his anxiety. You’re absolutely right about making sure this is thorough and I feel good about his health and safety before leaving him there because if they can’t promise that, I cannot trust them with him. He needs to stay hydrated throughout his stay

I have tried feliway products and I’ve definitely noticed some difference when I use the diffuser, not much with the collar but that’s just because he doesn’t usually wear a collar and just absolutely hated having something around his neck.

The vet that I have told me he only needs to be off methimazole for one week and then he should be all set for his appointment. I will confirm with them to make sure that’s correct.

I also absolutely think the radio iodine is worth it mainly from just seeing how low his energy level has been ever since I put him on methimazole, I couldn’t bear to see him live this way for the rest of his life. He is very kooky when he’s happy and I want my kooky cat back 😂
Absolutely!

Here is the study on low dose radioiodine treatment: Efficacy of Low‐dose (2 millicurie) versus Standard‐dose (4 millicurie) Radioiodine Treatment for Cats with Mild‐to‐Moderate Hyperthyroidism
Here is one on scintigraphy in general: Sci-Hub | THYROID SCINTIGRAPHY FINDINGS IN 2096 CATS WITH HYPERTHYROIDISM. Veterinary Radiology & Ultrasound, 56(1), 84–95 | 10.1111/vru.12165
Here's one on why scintigraphy is important in radioiodine treatment: Sci-Hub | Thyroid Scintigraphy in Hyperthyroidism. Clinical Techniques in Small Animal Practice, 21(1), 10–16 | 10.1053/j.ctsap.2005.12.002
And the Hypurrcat clinic website has a great, more easily digestible explanation too: Do Hyperthyroid Cats Always Need a Thyroid Scan? | Animal Endocrine Clinic
That whole website has lots and lots of hyperthyroidism information.

(If any of those links don't work, let me know and I'll attach the pdfs. If you do some research on your own and come across a paywall, google "sci hub", click the first link, and search the title or DOI number to see the article in full. It's an open secret in science academia.)

I wouldn't be too hard on personal vets for not knowing much about the radioiodine process. It's something they have to outsource and they don't have a lot of experience with it themselves. The radioiodine specialists themselves, I do have high standards for! I went to a research university for the treatment which, in hindsight, was probably not the best choice. Huge, busy place with lots of other things going on and vet students running most of the show. A small clinic is more likely to provide more targeted care and be concerned about the client's experience.

Feliway does make a spray that you can spray on his bedding, so that might help during when he's not at home.

My elderly cat was only about 5 pounds when she had the radioiodine therapy and she was fine. I actually couldn't make it to get her until Thursday, so she was there nearly 4 days. She was always pretty easy to please, though.
 
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