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question about my cats thyroid


Savannah Child
Hello all, I'm new to the board and have some questions about my cat chewie. He's a older male that has developed a thyroid condition. Unfortunately I'm not the most educated person in this area and I'm looking for some advice and suggestions in regarding what to do.

I will give some background on his condition but don't really know what details are needed to help answer my questions.

Chewie was diagnosed with a thyroid disorder about two years ago after a holiday trip visit my folks. He was having urination problems along with vomiting after every meal. After getting him to the vet they did a bunch of tests and discovered a borderline high thyroid count. I'm not exactly sure the exact figures but the vet recommended a change in his diet and was placed on a prescription food. The food is the hills brand y/d. Subsequent tests he's done have shown his thyroid numbers are now back to normal and according to the vet he's in good health.

Now my question is in regards to Chewie always acting hungry and what to do with him due to his special diet needs. Apparently the vet thinks that my routine of allowing a meal or two of chicken and fish per week, cooked without anything else other than some steamed vegetables and brown rice, is in appropriate for his needs.

My experience with feeding him nothing but the prescription food has resulted in weight loss and lethargy and lots of sleeping. The vet thought that he was loosing too much weight but it seems that the more of the prescription food he eats the more miserable Chewie gets. Thus the supplement meal I've been feeding him.

With the supplement meal of chicken or fish with rice and veggies he's been much improved with demeanor as well as regained lost weight.

After working with the vet to check his thyroid level after a supplement meal vs his prescription only thyroid levels it does show a "spike" in his results but the vet said it spikes within the "normal" range. The conclusion the vet and I have come to is to keep up what I've been doing to maintain Chewie's health and weight but need to stay vigilant with the testing to make sure were not overdoing it also.

This leads me to my questions..
1. What if any difference from a domesticated pat, is considered a normal thyroid reading. Especially given the different makeup of a Savannah cats genetics with the Serval's genes so recent in the genetic history?

2 Are there any other Savannah owners that have cats with thyroid issues?

3 If there are any other owners who have had thyroid health management with their cats how have they managed it? And what has the outcome been thus far?

4 The vet is suggesting that I go to a medication for Chewie's thyroid and a nonprescription food for better nutrition, vs the prescription food he's been doing OK on overall. The concern is the cost of the associated thyroid testing every few weeks currently vs once every few months on the medication in pill form. I'd appreciate any input and thoughts on this option.

Thanks to all in advance who read and respond with their advice and guidance. Chewie is an awesome part of my family and I hope to get him to lead as long and happy of a life as possible.

Ben (Chewie's owner)


Savannah Child
Also please feel free to ask any questions about Chewie as I don't really know what details to put out there to help folks paint a better picture. Also I post from my phone and the grammar and spelling was horrible in re-reading my post! Please excuse my horrendous phone typing skills! Lol


Staff member
My 16 yr old DSH developed hyperthyroidism and had chronic renal disease. I had her treated with radioiodine and she was cured. I chose the radioiodine because she was impossible to medicate -- it stressed her out too much; she was high-risk for anesthesia so I couldn't choose surgery. And, I wouldn't have opted for surgery even if she was a good candidate when there was a nonsurgical cure available. She was cured after 1 treatment and lived to nearly 19 yrs before her kidneys failed.

I don't think there are any differences between SVs and other breeds of cat when it comes to thyroid values. The drug used to treat the disease--Tapazole--is effective, can have side effects, and usually has to be given for the life of the cat. Here is some excellent info from Cornell that you can discuss with your vet:


Savannah Child
Thanks! I will read the links. I have good faith that the vet is trying to avoid that route if possible. His biggest concern is Chewie's diet/weight and how they seem to be interrelated. My concern is the constant blood work expense as money has just gotten a bit tighter recently so I'm looking for options to maintain his health. He's an awesome vet that specializes in cats and runs his own private practice here in Minneapolis and teaches at the UofM veterinary school also. The vets of the opinion that there isn't much in the way of resources regarding the newness of the Savannah breed as well as the genetics from the Serval. The vets comment about the serval's genetics being different from a domesticated cat is what made me wonder and if so perhaps what's considered 'normal' for a domestic cat is different from 'normal' for a savannahs genetics. The vet brought this up and has experience with lynx and bobcat in northern mn and said they have different 'normals' in his findings but alas there's not much information out there for serval's due to them being native to a different continent and lack of veterinary studies in that part of the world.


Staff member
Hyperthyroidism is due to a tumor. An x-ray will reveal its presence and if it is indeed there, the question about normal values between species won't matter. Although the radioiodine treatment can be expensive, it's cheaper in the long term than medication (assuming the cat is relatively healthy otherwise and relatively young) than medicating for a lifetime.

I paid $895 for the treatment in Oregon and there is only one place here that offers it. Prices in California and Washington were $2500 and above.

I hope everything works out for Chewie.

Brigitte Cowell

Staff member
You also have to realize that a bobcat and lynx are less related to the domestic cat than the Serval is. Hence it makes sense that their "normal" might be quite different. You could ask some Serval folk for thyroid values and see but my best guess is that you should be treating Chewie as a domestic cat and not fixating on his breed. Of course, you haven't mentioned what generation or % Chewie is...if he's a rare 87.5% F1 then I would definitely be more eager to look at what is the norm for a Serval! LOL!

When you feed your rice and veggie with chicken or fish, is there any supplements added to make sure this is a balanced meal? If not, maybe adding a supplement would mean that he would do even better on that diet. Maybe looking at what is different about the prescription diet for thyroid compared to normal cat food would direct what you should be thinking about in preparing meals for him. But I found when my older SV developed kidney issues the prescription diets he hated and they were low protein...yet taking away his kibble and feeding only a high protein canned food stabilized his kidney values until lymphoma got him a couple years later....


Savannah Child
Thanks. We have done a few xrays. They have yet to show a tumor. The radioiodine treatment here is also quite expensive. To clarify the vet is NOT wanting to take the radioiodine path until/if the xray shows a tumor. At this point (2yrs and 1 month) since his first diagnosis there is yet to be a tumor shown by xray.

The vet made the reccomedation of the food based purely off of blood work done. The initial tests 2 years ago was a complete screening and the vet as well as myself were stumped as to what was making him sick. Originally we thought it was a bladder crystal based on his actions and my experience with a previous male cat that suffered with them for years. Those tests came back clear. When the results of all the tests came in the only thing that was out of the normal was a antibody elevation and his thyroid level being 'high' but NOT into the realm where the vet was convinced beyond a doubt he was "hyperthyroid". He suggested that we try the food and see what comes of the diet change.

Since then his antibody levels became normal..his thyroid level was almost perfect.
This went on for a few months until about 6-7 months after the initial diagnosis when Chewie was in for a thyroid test and I brought up the weight loss and the vet noted he'd lost 4 lbs. The vet had me up the amount of food I was feeding him to give him more calories. Over the next 2 months the vet and I battled Chewie's continued weight loss he'd lost a total of almost 6 lbs by this point.

At that point I was worried as Chewie looked emaciated and wasn't near himself for normal activity or anything else. He was down to 12.5 lbs from a bit over 18 lbs when this all started. The vet was baffled as all of his blood work (another complete workup looking for other health issues) came back with results that claimed he was in perfect health. I took him to a second vet and had them do a diagnosis from scratch and came to the same results as the first vet's blood work, Chewie was in perfect health. The second vet also was suspect of the Hills brand food and Chewie's genetics but told me he's had problems with Hills food being overrated as to its nutritional value with various other pets.

This prompted me to do some experiments with the first vets guidance.
With a bit of research and intuitive reasoning we found out that the prescribed food had "hollow calories" that it was mostly made up of vegetable protein and little to no meat products with nutritional value. Think geletain with medicine mixed in.

All this lead me to develop a regiment of "real" food you or I would eat from the grocery store and reading this board as well as others developed a homemade cat food that was nutritional and as iodine free as I could make it short of a laboratory in my kitchen!

Thus far Chewie has been on this regiment of 5-6 days a week of the prescribed food from Hills. The other 1-2 days a week are of a large meal of chicken or freshwater fish with veggies and brown rice. This has been going on for almost a year now. About 10-11 months now.

I've worked with the vet quite closely for the first few months to establish the ratio of prescribed food to homemade food. We were doing almost a weekly blood test and constantly getting a thyroid reading that was on the high end of the normal spectrum to just past the acceptable range. We determined that by adjusting the 1-2 days so there wasn't a 5-6 day straight feeding of the prescribed food he actually lowered his thyroid count to the bottom of the "normal" range where he stays to this day. He's back up to his original weight about 18 lbs. He's playful and energetic etc.

The only down side to this is the constant monitoring of his thyroid and the prescription food that's a pain to get from the vet based on our work schedules. This is why I was thinking about going to the pill form of the medication as I can get it at a regular pharmacy and not need to chase the vet for food.

We also know that taking him off the prescribed food completely gets him back to sick. The vet and I tried this and decided to keep him on the prescription food at that time due to the experiment phase and not going straight to the pills instead of the prescription food.

The vet was merely making a suggestion to make it easier to manage this from my end, with the encouragement of keeping up the healthy food prepared here in the home to manage its ingredients.

Thus far its working good I'm looking to try other things at this point due to the time dedication this has taken and new obligations at work. But the bottom line is there's something up with Chewie's thyroid function that isn't warranting the radioiodine treatment based on the facts and test results and the vets reluctance to pursue that option due to his not finding any tumor via xray, borderline thyroid levels etc. That's what led the vet and myself to wonder if perhaps were missing something from the "normal" for the Serval genetics Chewie carries vs a different breed. The vet also claims in large cats (lions,tigers,etc) the thyroid levels "normal" are much different than a domestic cats levels, so we are purely speculating but still wonder..

Hope that helps give some background on it all. I guess Chewie has a health problem but its not full blown to the point where radioiodine is worth the risk is how the vet phrased it..and pill form just seems more convenient with upcoming changes in my life vs the prescription food route we've been using to tackle the problem.


Savannah Child
Well I'm not exactly sure what his genetics % is but I can tell you his history up to the Serval he was bred from.

Let me be clear up front about a few things also..I'm not a breeder and have no understanding of how the f1-f2 thing etc works.

Chewie is a rescue cat. He came to me from some friends that rescued his mother from some less than honorable folks who imported his mother and grand father illegally from Africa. Both were wild Serval's caught in the wild for the black market. They currently live at a private animal shelter/rescue in rural Minnesota.

Chewie came from a litter that his mother was pregnant with before she was put into the shelter.

The folks that run the shelter are friends of mine/excoworker. They know based off reports and records from the folks Chewie's mother was seized from that she was bred with a Savannah (tabby/serval mix) named Max who's father was the male serval that was also seized (Chewie's grandfather). I don't know what that makes him exactly other than a Savannah. The vet I work with at the UofM has done a genetics test and confirmed his mother is in fact the wild serval in the shelter and his grand father is the male in the shelter. It also showed his father that went to another home.

The only thing I know that the vet has taught me is Chewie is at least 50% serval and likely higher based on the short family tree but I had to have him neutered as a part of the adoption process from the shelter as well as sign some other agreements. He still has some wild/feral characteristics but has settled into domestic life quite nicely. There's other criteria involved where I live in Minnesota with exotic pet licensure as well.

I try not to get hung up on the Serval genetics at all but the vet seems to think it plays a part in this thyroid problem we've been maintaining. Up until it happed a couple years ago he was perfectly healthy and happy. I just wanted to ask about it for the sake of more knowledge to share with the vet. The vet is a HUGE cat fanatic and is always happy to see Chewie. The vet has been practicing for almost 40 years as a specialist in felines. He says its been the highlight of his career to get the pleasure of being Chewie's doctor! Lol. I get the pleasure of owning him and putting up with his mischief!

Chewie lives happily here with myself a black lab and until a few months ago an old basset hound who died of old age. We have quite the odd family but I think our eccentric natures are one thing that makes us cool.

If you understand the f1-etc thing I'm more than curious to understand how it works. I also understand that there's no surefire way to know short of a genetic test which has sort of been done to rule out he WASNT 100% serval when he was a kitten. He would have been put down if that was the case.

Brigitte Cowell

Staff member
Wow, that's some history for Chewie...I'm trying to get that straight in my head. His mother AND his paternal grandfather are Servals? And Max, who is Chewie's father, is the son of a Serval and a domestic cat?

Do you have that genetics test result at all? This is fascinating as this would be a world's first for an F1 male (the F stands for filial generation away from the wild cat) to have been documented fathering a litter. And with a Serval female no less, as there have only been a tiny handful of cases where a Serval female gave birth to a Savannah litter and I believe with Chewie's age that would make him the world's first of this also!

Added to the "firsts", this is the first known Savannah produced from Servals from Africa as the Servals that have been used in Savannah programs up until now were all captive bred for generations here in the US!

This would make Chewie a 75% F1, so I would love to see pics of him. 75% F1s are very rare (even when the Serval is the father).

As to the genetic testing, from what you have said there was parentage testing done on all the cats hence you should be able to prove this... the vet at UofM should have that for you. As I said, I would love to see those test results that document this history!

But if Chewie is indeed 75% Serval then you do need to research values for Serval as he is more Serval than domestic in heritage.