I-131 Treatment For Hyperthyroid Cat

[chris gadbois]

I talked with her I-131 vet just now. She says it's completely normal. She said every cat is different. Some take weeks to shut down the tumor, others take days. After the tumor is gone some cats are a little sluggish, sleep a bit more and also less hungry. You were right Antonio65, she is likely HYPO-Thyroid right now until the healthy part of her thyroid kicks back in and starts creating T4 again.

Onyx's body has been on 'full blast' for a long time, and we finally shut off the rocket fuel. It almost literally happened overnight. Her body is just resting/recovering (I think I'll let her sleep now).

 

[molly92]

Wendy just got her treatment and after 2 nights at the vet, she is home!

Here was my experience with Michigan State Veterinary clinic if anyone's interested:

Apparently most places in the country do a standard 4 millicurie dose of radioiodine for all cats, and MSU is the same. In theory the overactive part of the thyroid absorbs so much of the iodine that overdosing is not a concern. However there are many vets that are refining their approach and tailor dosing to the thyroid tumor size. Dr. Mark Peterson has written extensively about it, both on his website and in published papers.

MSU also does not do scintigraphy for this procedure, probably because they don't need it for calculating dosing I suspect.

So, after a weekend of reading papers and veterinary textbooks, I came armed with information to our visit on Monday. They wouldn't budge on the scintigraphy part-which I had to concede because if they don't normally do it and don't know how to do it's probably for the best that they didn't try it, and Wendy's other scans were evidence enough that she didn't have a metastatic tumor so that was not a concern.

My next point was that Wendy seemed to be in the mild to moderate hyperthroidism range, given that her thyroid panel numbers were just outside the range and her thyroid wasn't palpable in a physical exam, which they agreed. So I asked about a study that did 2 millicurie doses instead of 4, and foind just as good curative success but lower rates of hypothroidism, which was better for the kidneys (Wendy also has CKD). In the end, they agreed to do a 3 millicurie dose for her, although based on what I've read I think 2 would have been more than enough, but they were not comfortable with that so we compromised.

Well, at any rate, we're home! We've been hime for half an hour and Wendy has spent a good 15 of those minutes at the water fountain-she's always thirsty, but now especially so. I don't know if this is a side effect or the car ride made her thirsty or she just missed her fountain, but I'm not too worried. Very interested to see how she does in the next few weeks and how her checkups go in the coming months! I feel like her fur is already looking better, but maybe I'm imagining that...

 

[Antonio65]

Apparently most places in the country do a standard 4 millicurie dose of radioiodine for all cats, and MSU is the same.
[...]
MSU also does not do scintigraphy for this procedure, probably because they don't need it for calculating dosing I suspect.

Luckily, when my cat had to do the same treatment, she was tested, she got a scintigraphy done and the radio-iodine dose was tailored on her needs, at 1.2 mCu.

Well, at any rate, we're home! We've been hime for half an hour and Wendy has spent a good 15 of those minutes at the water fountain-she's always thirsty, but now especially so. I don't know if this is a side effect or the car ride made her thirsty or she just missed her fountain, but I'm not too worried. Very interested to see how she does in the next few weeks and how her checkups go in the coming months! I feel like her fur is already looking better, but maybe I'm imagining that...

My former vet always told me that when a cat spends a length of time outside home, the first thing upon returning is that they drink a lot, not because they're thirsty, but because they think it's a way to feel they are home again.
As a matter of fact, when I boarded my cats while I was on holiday, they were always drinking a lot as first thing at home.

As for the fur, I think it's just your imagination.
The effects of the radio-iodine take some weeks to be visible.
Good luck!

 

[chris gadbois]

I wish they had a handout for 'What to Expect AFTER the I-131'. I've been on the phone with Onyx's I-131 vet (who has really been fantastic with me) with some follow up questions.

I had thought that the tumor (once radiated) will be killed off and her T4 counts would slowly come down and work they way back to normal. However Onyx goes thru 'spikes' of Hyperthyroid symptoms. I'm mean, she is doing really great, but some days her appetite is huge, somedays normal. Once in awhile I see the eyes dilated and her tail twitching like crazy.

The vet said the tumor does not just die evenly. Some tumor cells take longer to die, the healthy part of her thyroid has also been scarred by the tumor and it takes time for her body to even it all over. I thought all along that the symptoms would just slowly diminish and fade away...but in truth it's more of ups-n-downs for a couple of months.

We just finished the 2 week litter restrictions period, 1 month follow up Blood Panel in a couple of weeks.

Just to watch her sleep so peacefully (again) has already made all of this so worth it.

 

[Antonio65]

I can't tell if what you're seeing is normal, because my cat had an uncommon form of hyperthyroidism, with symptoms and signals that were completely different from a usual HT cat.

What I remember is that after only one month, the blood test didn't reveal a sharp difference, though it did show a good trend towards an improvement.

 

[molly92]

Interesting. Thanks for the info from your vet!

We are now 5 days post treatment and Wendy is just nibbling at her food here and there, mostly with a lot of coaxing from me. When I first adopted her it was a struggle to get her to eat for a week or so, so I think part of this is her reaction to stress, and part her hormones being weird.

She hasn't vomited once though, whereas before she was starting to vomit every couple of days. My I-131 vet said a lot of cats stop vomiting immediately after, so I'm keeping my fingers crossed.

 

[chunkykitty]

My beloved and the late Mr. Baby Cat had low stage CKD. When he was dx with hyperthyroid the vet immediately recommended the gold standard -- radiation treatment. But after reading that it could irrevocably cause additional kidney damage in a CKD cat, I asked to try the pills first. After he was on them for a month his CKD test skyrocketed. I am glad I didn't put him through the radiation treatment.

We lost him about a year later due to a combination of illnesses, but we had many of his wonderful 17 years together.

 

[chris gadbois]

Hyperthyroid CURED!

I got the call for Onyx's blood work this morning. Everything is great. Her liver, kidney counts are all perfect. Diabetes numbers are also on the low end of the spectrum. T4 count was at .2 (which is low) but her vet believes that the thyroid is healing and that number should stabilize by the final 3 month post blood test. She even gained a half a pound.

Onyx has had a rough ride that last couple of weeks. Sometimes she was normal, other times hyper, but the ones that scared me was when she 'crashed'. She would just sit in the Sphinx position, head straight down. I guess it's just part of the healing process, but it's hard not to worry when you see her like that. Happy Day!

 

[Antonio65]

Great news!
Yes, at first the thyroid is a bit slow and seems not working properly, but it's just a matter of time, in about three months time all will be back to normalcy!

 

[molly92]

I have an update on Wendy's progess (finally got her month-after thyroid bloodwork results back):

Her thyroid numbers are all in a normal range now, with a few on the low side. I'm viewing this as a snapshot not a definitive endpoint, because same as with Onyx, things have been a bit up and down! Mostly her appetite has been swinging back and forth, although the extremes are becoming less and less so. She'll eat very little for a few days, then her appetite will pick up again, then it will go back down, etc. I haven't been told this exactly by a vet, but just based on what I know about biological pathways and feedback loops, it makes sense that a drop in thyroid hormone could trigger the thyroid to over produce and vice versa, so I'm not concerned.

What I think is more telling than the bloodwork is her symptoms, or rather the lack of! She has thrown up only a couple of times in six weeks, very small amounts, whereas before she was starting to throw up every couple of days. Her fur looks totally different-no more sticky saliva! Her blood pressure is down to normal, and she hasn't gained weight yet, but the vet said she looked much more filled out and hydrated. I'm very pleased!

Her BUN numbers did go up, because she does have kidney disease. So I'm working on diet and supplements with the vet to manage that, but it was definitely worth it. Much easier to deal with one organ declining as opposed to all of them.

 

[chris gadbois]

I wanted to come back and give the 3 month blood test follow up for anyone interested in the I-131 treatment. Her blood test came back perfect. T4 count of 1.6. Over the 3 months since her treatment onyx has going thru some ups and downs, mostly in her observable behaviors. When she was not feeling her best she'd start out by sleeping in the Sphinx position. She'd also complain a bunch when she was feeling down. These behaviors declined in both duration and frequency over the last 3 months. Onyx will also want to sleep on my lap ALOT! Something which she has never done before.
The T4 test gives you snapshot of her thyroid function at that current time. So I also opted to test her T5 counts. (That is how much of the thyroid hormone is actually floating thru her bloodstream). If that number was high then we would know that her thyroid is under-performing and she would be making extra hormone to compensate (Does that make sense?). Anyway, those numbers came back right in the middle of the 'normal' range.
The end result is Onyx is in perfect health and Hyperthyroid Cured! Her fur has gotten lush again, she is a purring, over-eating beautiful snuggle bug of a cat. With an added bonus feature - she is now a Lap Cat too....i love that!

If you have a HT cat I can't tell you enough how this solved the problem. If you are considering this treatment, it is 'the cure'. At the end of all of this the total cost was around $3000 (from the original post here to this present one). That is alot of $$ up front, but it comes to same as a couple of years of pilling and bloodwork.

If you ever have any questions, please feel free to email me and ask. Thank you to anyone who posted here and offered suggestions. Maybe someone reading this 'diary' will get some help in understanding their pets health.

One last shot of Onyx i just took, and happy Holidays to you all.

 

[Antonio65]

What a gorgeous cat she is!
Congratulations on your committment and effort, you have both been great!

 

[chris gadbois]

Hi,
I'm 6 months POST I-131. I'm fat, furry and happy again. I still sleep on my Dad whenever possible. At night if he sleeps facedown I like to lay on his back and purr in his ear. I know I'm a pain in the ass, but he loves me.

 

[susanm9006]

So beautiful.

 

[Antonio65]

Lovely!
You did a great job!

 

[chris gadbois]

Hi folks. I'm sorry to anyone who had messaged me...i never saw them until today.

Update - 18 months later and NO recurrence of Hyperthyroidism. 1 shot -1 week stay - no more pills, no more worries. Onyx recently had a different problem that we did a full blood panel for and her T3 & T4 counts were all in the normal range. Can't say it enough - if your cat is a good candidate the I-131 IS the way to go.

 

[profcat]

Our Daisy is going on 3 since since her I-131 and she's doing wonderfully as well! Thyroid levels have been perfect I'd recommend everyone get this done! She wasn't hard to pill, but was allergic to the thyroid meds, and it's just good not to have to give her something every day!

 

[buffy2011]

Hi folks. I'm sorry to anyone who had messaged me...i never saw them until today.

Update - 18 months later and NO recurrence of Hyperthyroidism. 1 shot -1 week stay - no more pills, no more worries. Onyx recently had a different problem that we did a full blood panel for and her T3 & T4 counts were all in the normal range. Can't say it enough - if your cat is a good candidate the I-131 IS the way to go.

Curious about some things after the I-131 therapy. My Bella was a candidate for the shot. So we went ahead and did that. She did great even being confined,which I thought was going to be tough on both of us. So after the confinement she was doing quit well, then she had diarrhea and vomited a few times, and then all was well again. We just had her one month blood work done and the vet was happy with the T-4 levels. She said they were 2.2, and all the other blood work looked good. The other day she started acting not with it, like she did when she was hyperthyroidism, but she also vomited. So am I to expect this on and off for a while, is this normal, I was told it was but would like some thought from someone that has had this done on there cat.

 

[molly92]

Curious about some things after the I-131 therapy. My Bella was a candidate for the shot. So we went ahead and did that. She did great even being confined,which I thought was going to be tough on both of us. So after the confinement she was doing quit well, then she had diarrhea and vomited a few times, and then all was well again. We just had her one month blood work done and the vet was happy with the T-4 levels. She said they were 2.2, and all the other blood work looked good. The other day she started acting not with it, like she did when she was hyperthyroidism, but she also vomited. So am I to expect this on and off for a while, is this normal, I was told it was but would like some thought from someone that has had this done on there cat.

Yes, it is normal for the thyroid levels to cycle up and down for a few months until they normalize after about 6 months. You should have a vet visit scheduled around then to recheck her thyroid levels again. In rare cases, the dosage is not high enough and a second round of I-131 is needed, but I have never heard of that happening personally.

While my cat threw up less often after the I-131, and her thyroid levels did become normal, she still did throw up occasionally until I learned she didn't tolerate some foods well. So it's possible that by curing the hyperthyroidism, you reveal which symptoms were caused by the hyperthyroidism and which might be caused by something else, especially if your cat is older and has accumulated a couple health issues.

 

[buffy2011]

My main issue with Bella is the diarrhea. I keep trying to get some dry food back into her diet, so my other cats can have some. Everything has to be put away because of Bella. So I have been giving her a small, very small amount a few times a day. Now she has the diarrhea. But the vomiting sometimes goes along with it. I'm trying to get dry food back into her diet, but this hyperthroidism could be the problem too. I have been researching on what is the best dry food for her. There is just so much to consider. I was thinking the flavor was a problem, so I was going to try something different. She use to eat dry all the time and no problem and then everything went wrong. Maybe I just need to wait out this hyperthroidism first before we start on the food. But my other cats are suffering because of her. There is not where in the house that is safe to feed my other cats, Bella is smart and she will find it or she follows me all around. She is due for her second blood work in June. Her levels were great the first time around. But with me giving her this dry, could it affect her blood work, because she is having diarrhea and some vomiting. If there is one there usually is the other or it will follow soon. Even if I buy a sensitive stomach food, it is still hard food, so would that make a difference. I was thinking of a dry that is a little softer food. Can't even give her treats of any kind, she loves them and will chase you all around the house for them, but she get diarrhea after a few days of them. Does anyone else have this dry food problem. thanks