Hyperthyroidism is Increasingly Common Among Older Cats

If you have a kitty, you have probably heard of feline hyperthyroidism. Chances are even better if your Fluffy is a senior. That’s because feline hyperthyroidism is the No. 1 endocrine disorder of aging cats.

Hyperthyroidism is caused by an overactive thyroid gland. The opposite condition is an underactive thyroid gland, or hypothyroidism. People can be affected by either condition. Interestingly, for our four-legged family members, hyperthyroidism is virtually exclusive to senior cats, and hypothyroidism to dogs.

In fact, hyperthyroidism is so common in aging cats that standard wellness guidelines recommend screening for this disorder annually once a cat turns 7 years old.

The initial signs of an overactive thyroid gland can be subtle. As the disease progresses, your kitty may begin to show more obvious signs of a problem.

Early detection is key to successfully managing this disease and Fluffy’s overall health. Although some consequences of hyperthyroidism are reversible once treatment is established, others are not.

Excess thyroid hormone affects virtually every organ in the body. It increases metabolism, causing weight loss despite increased appetite. Fat and muscle are burned away. If left untreated, hyperthyroidism is a wasting disease.

Initially, you may not be aware that your cat has lost a few ounces. Or, you may erroneously think that Fluffy’s diet is finally taking effect.

Your veterinarian may examine Fluffy and feel an enlarged thyroid gland in his throat. This is usually due to a benign growth of thyroid cells. These abnormal cells don’t listen to the cat’s body’s signals to turn off hormone production.

Rarely, the enlarged thyroid gland may be due to cancer. This occurs in 1 to 2 percent of hyperthyroid cats. These cats initially have signs similar to other hyperthyroid cats, but the abnormal cells eventually metastasize, causing tumors elsewhere, such as in the lungs.

As metabolism increases, the heart works harder. This muscle pump changes in size and dimension due to the constant stimulation. Eventually, this leads to heart failure.

The kidneys take a toll as hyperthyroid blood is pounded into their delicate filters. Ironically, hyperthyroidism can initially mask the signs of kidney disease, but the damage is occurring nevertheless.

Blood pressure may climb and affect a variety of organs. For example, cats may become blind from retinal detachment.

Uncontrolled hyperthyroidism increases anesthetic risk. Safe anesthesia protocols include screening all senior cats for hyperthyroidism before performing elective anesthesia.

Fortunately, hyperthyroidism can be easily diagnosed with a simple, inexpensive blood test. Occasionally, thyroid levels can be in the “gray zone.” These cases warrant monitoring until their thyroid trend can be determined.

The good news is that most cases of hyperthyroidism can be successfully managed.

Daily, lifelong medicine controls hyperthyroidism in many cats. Most kitties tolerate this quite well. However, 10 to 15 percent become too ill from side effects of the drug to continue. Risks include severe nausea, liver disease and blood cell destruction. Cats need to be monitored closely for life-threatening risks, especially when starting or increasing this drug.

Unlike drug treatment, radioactive iodine therapy is a permanent remedy for hyperthyroidism. Certain government-approved centers provide this treatment by injecting affected cats with radioactive iodine. The sick thyroid cells attract this medicine, which in turn destroys them. Not all cats are good candidates for this procedure, but for those that are, the results can be marvelous.

Another option is to surgically remove the sick thyroid gland. This is also a permanent treatment, but involves placing a potentially unstable patient under anesthesia. Sometimes, the adjacent parathyroid gland is also damaged or removed, causing possibly severe calcium derangements.

In recent months, a novel therapeutic diet has been developed by a major pet food manufacturer to treat hyperthyroidism. The food is safe and effective, but cats must stay on it forever and cannot have treats or other nibbles of food. This can be especially challenging in households with multiple cats.

Research is ongoing to better understand what causes some cats to become hyperthyroid.  We know that the incidence of this disorder is increasing.

This is partly due to the increasing lifespan of cats over the past few decades. Since hyperthyroidism is a disorder of senior cats, we expect to see the incidence rise with a larger senior feline population.

But the incidence of hyperthyroidism is increasing faster than the senior cat population. And indoor cats have a higher risk than cats that go outside.

Various environmental factors, including canned cat food, flea products and cat litter have been studied as possible causes, but none has been found to be associated with hyperthyroidism.

A more recent theory suggests flame retardants in furniture and rugs as a possible culprit. More research is needed to determine whether there is actually a cause and effect relationship.

The bottom line: You can help Fluffy by having her thyroid checked every year after age 7.

• • •

Dr. Heidi Bassler practices at Bassler Veterinary Hospital

46 Responses to “Hyperthyroidism is Increasingly Common Among Older Cats”

  1. Sarah says:

    Thank you so much for this informative article. I needed this information for a veterinary technology course I’m taking (a case study on a hyperthyroid cat), and could not find the information on the symptoms of untreated hyperthyroidism! Thank you, thank you. I’ll be saving this article for future reference.

    • lauren weber says:

      feel free to contact me. my 17yr old cat Nick, is hyperthyroid and is not being treated as the medication makes him vomit.amazingly he is still with us.

      • Cheryl says:

        Hello,we too have a17 yr old hyperthyroid cat who does not tolerate either the meds for hyperthyroidism or high blood pressure. She caterwauls at night–sounds like real pain but vet says it’s from the hypertension associated with hyperthyroidism. Do you have that problem? I don’t think there’s a chance she will try that diet food as she’s a very picky eater. Any advice, suggestions??
        Thank you
        Cheryl

        • lauren weber says:

          Hi Cheryl-
          No caterwauling-Nick had always been “silent bob” (from the movie, Clerks). But he just eats and eats… I have not tried the special diet because I cannot guarantee that he wont eat anything else.

          • Selina brady says:

            Hi Lauren,

            My cat ash has just been diagnosed with hyperthyroidism, hes 14yrs old and our vet has given us two options, medicate or radiation iron therapy,now we are trying to make a decision what we should do, we are seriously thinking of going with the iron therapy the only thing is its out of town for us and our cat just wouldnt handle being away from home for all that time. What i would like to know how is everything going with your cat as you have decided not to go ahead with treatment,we are also considering this option,sorry for the long question, but thank you

        • Emma says:

          That late night yowling is perhaps the #1 sign oh Feline Hyperthroidism. I thought it was just part of my baby’s personality!
          Secondhand cig smoke is unfortunately a likely candidate for disease onset, as well as Sleep Apnea/snoring, in our furry friends.

          **WARNING** I do want to point out that because of the widespread effects of excessive thyroid hormone on the body, your cat may also be an insulin dependent Diabetic. Our vet missed the thyroid issue and was grossly over medicating with Insulin. We almost lost him. Beware of rapid weight loss, especially back by the hips & tail and an irregular, almost greasy coat.
          Cats being one of the few, if not only, species able to go into Diabetic remission – they can be cared for with only a little extra help and some simple, regularly scheduled routines you’ll need to adopt while transitioning to Insulin. Walmart does make an affordable option available once original diagnosis is made.
          My old man will be 14yr. in a few months & we’ve been playing this game since he was about 8 yr old. We’re doing ok.
          Anyone with questions or wanting some advice/ someone to talk to… please don’t hesitate to reach out and best of luck to everyone.

      • Evie burke says:

        have you tried the Science Diet Y/D food for hyperthroidysm? I had my 11 year old on the food and she threw up everyday several times a day. I now have her on the medicine and she no longer throws up and is starting to gain weight. I know you said the medication didn’t work, but maybe the food will.

        • Brooke says:

          our kitty now 16plus.. had been on prescription for hyperthyroidism for couple years now. she too was throwing up daily..multiple times a day 🙁 i was given cans of Royal Canin Recovery (prescription only, of course) eventually getting our own script. The pill w/ the food did work.she eventually stopped liking that food (canned) . she never really gained but wasn’t losing anymore. she stopped throwing up.. which made us both happy!.. however the pill is no longer working:( Dr. won’t renew prescription 🙁 w/o basically $250 visit for labs. Not sure we want to put her through that stress (strictly indoor Siamese) looking into alternative means. I don’t have 1400$ for R.I.Therapy
          I might try Recovery Diet or the Thyroid canned food.

          • Kate Kores says:

            Hello. Why the $250 for recheck. Office visit should be half for recheck and blood draw for only thyroid should be $40 and pills which may increase or decrease the dose is about $18. Does your vet overcharge.

      • Jo Ann says:

        My cat is also intolerant to the meds also. What do you do instead? My gal is 16.

      • Jon says:

        My Persian has lost its voice, according to the vet it is hyperthyroidism but my vet is trying to push me into having expensive treatments to see if he has cancer. He will be 11 this year.
        He has not showed any illness signs and appears to be fine

        • Cathy says:

          My cat 13, he had a blood test & he has hyperthyroidism. He couldn’t take the medication and refuses to eat the Hills Prescription Diet canned food the vet prescribed. He started with shots of B12 a month ago. He’s gaining weight, his coat is shiny and he looks 100% better!

          • Cary says:

            I wonder if I should ask about the B12 shots. My 14 yr old cat is going to the vet today as I am almost positive she is hyperthyroid. she has all of the classic symptoms. I am anxious to see what he suggests as far as treatment. The radiation treatment is not going to be an option due to cost. I am worried about all of the side effects I am hearing about the daily thyroid medications. She doesn’t vomit but maybe a couple of times a week right now, so I would hate to give her medication that causes her to do that. I don’t mind paying for the prescription food if it helps her. I am just so confused on what is going to be the best option.

          • Nancy Wright says:

            Thanks Cathy my cat is 18,won’t take pill much so when he does bad side effects,used the special food he does not like it.I am using natural liquid drops i get from online for cats thyroid problems.From web site- only natural pets it’s about $18.00.Do all vets use b-12 shots,how does that work?Any help you can give me would be great the drops are keeping him alive but not gaining any weight. Thanks Nancy

          • Leigh says:

            So many of you have mentioned the cost is the reason you will not consider the radioactive iodine therapy. It may seem like a lot up front, but to CURE your fur baby of this awful condition is so worth it. I just went through it all. And honestly, everything leading up to the treatment was a million times worse. And not to mention EXPENSIVE! From the medicine making her sick, extra vet visit, stress. I was able to get her the treatment with Care credit. Sadie has had her final blood work clearing her of the disease and we couldn’t be happier. I have also put her on a raw diet. Unfortunately, the commercial food companies are causing a lot of the medical issues cats are having. Remember, they are 100% dependent on us to care for them. It is up to us to do our very best and give them what they deserve. So stop messing with all the meds and just cure it once and for all.

  2. dave says:

    my elderly cat has this problem… what is the medicine she needs to fight this?

    • Elizabeth Ingram says:

      The medication you require is methimazole it can be either in tablet form , which must be given whole not broken up, or a liquid which is squirted directly into the mouth, and that one’s marketed under the name Thyronorm.
      If you cat is indoor only and you can ensure exclusivity of feeding Hills Science produce yd prescription diet, which restricts iodine and will bring thyroid hormones back to normal levels, but it must be fed to the exclusion of all other foods. Hope this helps

  3. Barbara Keys says:

    Is it part of the desease, for my cat has this problem. She drinks a lot of water, so pees a lot, & it is in huge clumps, like clay, then gets like cement, very hard to clean out of ,litter box. Is she in pain also?

    • Barbara Keys says:

      Willy you answer my above question. Barbara Keys

    • Pam says:

      The amount and frequency of urination is what is key here. Not your cleaning litter box woes

      • Pinky says:

        Wrong so wrong.. That’s not at all what she said.

        • Denise says:

          Our kitty has the same issues with the litter box, she has diabetes so I assume it is the sugar that makes the clumps like that, I would have to scrape the litter box just to scoop it. I changed to pine pellets and easier to clean. My other kitty has just been diagnosed with hyperthyroidism and it was making him drink a lot and lose weight just as diabetes did but his litter is not as bad. The vet diagnosed him with hyperthyroidism. So I have one receiving insulin injections and the other getting pills. I’m checking into the R131 procedure for my fella with hyperthyroidism though hoping that will be a cure instead of just managing it with medication.

      • Amanda says:

        There wasn’t a need for the catty response. Any time someone’s fur baby has issues; I’m sure like I’m doing now, is trying to find answers and similar stories to help make the right decision for treatment.I sadly had to put to sleep Caesar; Dec 7,2018. He was only 3 1/2. His twin brother(zero health issues) is freaking out and I’m still feeling as though I gave up on him. He has had health issues since he was about 1. Our older cat Mayhem has now been diagnosed with hyperthyroidism. Super picky eater and there is no way she would handle meds twice a day and be happy. So long winded; but sometimes it’s better to cut out the sarcasm when someone is having genuine stress and concern for a loved one.

        • Mary H-M says:

          First, so sorry to hear about losing Caesar. It is never easy and I feel they take a piece of me with them each time.
          Currently my 10 yr old, Buttercup, was diagnosed with hyperthyroidism. All the symptoms incuding vomiting and diarrhea. We tried the methimazole pill. We made it all of one night. So bitter and she started drooling. So I googled and found that drug can be made into a white gel cream to go inside upper ear. Everything was going fine for about 10 days but then the vomiting came back. I’m praying that it is from eating too much too fast. So smaller amts more frequently. Vomiting stopped but now started back a little bit.
          I’m just so confused. Vomiting can be part of the illness but it is often a side effect from the med in a small percentage of cats. Husband says take her off it- period. But I keep reading info and seeing what happens if left untreated. And she can’t do the radiation treatment. Although I would pay it in a heartbeat.
          Sorry for rambling. Just feeling frustrated and lost. I appreciate coming on here to see different ideas. My sympathies to all the kitties suffering.

    • Jeanette says:

      Excessive thirst and urination can also be a sign of diabetes. That’s what tipped me off to my sweet boy’s diabetes. With insulin and regular blood sugar checks at home, he was with me until age 16.5

  4. Vickie Davis says:

    My 16 yr old female cat was diagnosed hyperthyroid. She has lost a 5% of her body weight. She has been taking Methimazole 5 mg 1 tablet twice a day. Also, Science Diet yd prescription. I crush her tablet an put it in her food so she’ll take it without getting her upset. She shows no sign of getting better. Besides she has started urinating outside of her litter box. I have been considering having to put her to sleep. I can’t afford to take her to a specialist.

    • Before you make that decision, contact the HSUS and they might have contacts in your area that can help with financial grants. If you live in LA or Orange Counties in Southern California, then we have an Angel Fund Grant that may help. Email ahfed@animalhealthfoundation.org if you are in those So Cal counties.

      Also, here is help with your decision: http://www.animalhealthfoundation.net/how-we-help/quality-of-life.html

      Maybe ask you vet of they know any financial aid services in your area.

      • Mercedes says:

        I think my 15 year old cat, Munchie, suffers from hyperthyroidism. Her appetite is normal but I noticed that she appears to be losing weight. I noticed this a while ago but I didn’t think much of it because she’s eating well and she’s active. However she yowls a lot. Do you think that she is in pain? Her water intake appears to be good.

  5. AmberJennings says:

    I was given the option of pill or topical cream to rub on inside of the ear. He was treated for two years, pills first, topical, then back to pills before having to do what was right for him at 17. He did a great job. never heard about the food. But, had multiple cats anyway. Sorry for anyone having to go through the pain.

  6. Michelle Mitchell says:

    My cat is 19 years old and she was placed on thyroid tablets last November 2017 to increase her weight. She to this day has not gained any weight whilst been on this medication and to actually try to give her it is an absolute nightmare and really stresses her and myself out so much that is is worth carrying on with the medication as she’s eating and drinking well going to toilet as normal and even still plays with string and balls. There is no change in her whatsoever since taking this medication. I personally would not like to continue with the medication as i hate stressing her out and just to give her the best quality of life what she has got left. Am I wrong in saying that? As she is not going to live much longer.

  7. Michelle Mitchell says:

    Hi i left a message yesterday about my 19yr old cat whose on thyroid tablets since last November and there has not been any change whatsoever. All I’m doing is stressing her out and it’s upsetting me really bad i hate this so I’m really wanting to stop the medication for this reason as she is so old and delicate now all i want is to give her the best quality of life of what she has got left which won’t be too long now. She’s eating and drinking and using the toilet as normal also she still play’s with balls and string she is showing no signs of anything different from before the medication till now as taking it. Please can you give me some advice on this stressful situation its causing both of us. Thank you. Mrs Christine larner

  8. Meghan Bright says:

    My cat is about 16 and was just diagnosed with hyperthyroidism. He’s lost about a pound or 1/10th of his body weight. I just started him on the Methimazadole ear cream. He’s going in for the Radiation Treatment in Denver next month. He will be 4 days in the clinic and then home with limited human contact for 2 weeks. If the thyroid responds well, he’ll have a clean bill of health for the next few years. It costs $1300 but it’s cheaper and easier than medication administration in my opinion. This cat has been my companion for his entire life and there isn’t anything that I wouldn’t do to keep him healthy and happy.

  9. April Miller says:

    My 16 yr old male cat has been using transdermal meds for hyperthroidism for many years, very successfully. It eliminates the stomach issues that may occur with the oral meds.

  10. Fran Gilbane says:

    Hi. I’m in the UK and my cat has undergone the radioactive treatment today. He has been on the twice a day liquid drug treatment since April. We were told it was ok to put it in a little bit of food, a process which made it a lot less stressful for both him and us and definitely much easier than pills. A big deciding factor in going for the radioactive treatment was that the vet said the drugs can reduce lifespan by as much as half compared to the radioactive treatment and no treatment at all will eventually be fatal. In the UK the cost is £2200. We were lucky enough to have pet insurance, hence we have been able to do this. If we couldn’t though, I would definitely recommend the liquid and would suggest putting it on a little bit of sandwich meat, which always gets wolfed down. At one point we did try to increase the dose but that made him sick. A lower dose, as suggested by the vet, did get his levels down to an acceptable, albeit not great, level. Good luck.

    • Ruth Corbett says:

      Hi Fran
      Could you let me know what the amount of the lower antithyroid medication was? My boy is on thyronorm and is not doing well at all he has a heart condition and is on libeo and atenolol daily..thanks

  11. Suzanne Law says:

    Hello Everyone,

    Thank you to everyone that posted about their fur babies being diagnosed with hyperthyroidism. I suspect my 13 year old male cat has this as he lost so much weight, eats all the time, and has diarrhea. Also he is drooling a lot so I suspect teeth problems even though he had his teeth cleaned two years ago. I don’t know if he can tolerate being under anesthesia again. He is going to the vet this Friday and after reading your comments I will know what to expect. Thank you.

  12. Donna Patterson says:

    My baby is a 17 year old female who was diagnosed with hyperthyroidism about 6 months ago. Our vet said she would not survive surgery. Her kidneys are borderline. She does not appear to be in any discomfort. She has lost considerable weight, now almost skeletal, but she eats very well, drinks normally, urinates regularly, and has regular movements. She has energy in that she runs around from bed to food to water to litter and back to bed. She sleeps lots. She has always been a bit high strung, so my thoughts are to keep her comfortable without any stress. We have 4 other cats who adore her. She is the queen. As long as she appears to be comfortable, I think that I will just keep her as is. My guess is that she will not be with us much longer. My wonderful vet will come to our home and help her pass over if it becomes necessary. Am I wrong in feeling this way?

  13. Jessica Nesci says:

    I have a 12yo cat who was diagnosed with hyperthyroidism about 7 months ago. He takes 5mg tablets twice a day and he had been doing well but now he has began to lose his function in his hind legs again which is a common symptom of this disease. I am worried the medicine is no longer working, is he just having an episode or what?

  14. Hilary says:

    I have had experience with two Hyperthyroid cats, both of whom were treated differently for different reasons. The first cat, Dora, was already quite an old lady when diagnosed. She was a rescue so we were never exactly sure about her age, but she was probably around 16 at diagnosis. She was a sweetheart who was super easy to pill and tolerated the methimazole well, so I chose to medicate her rather than go with the expensive radiation therapy. We had another 3 years with her before having her euthanized for extreme kidney failure and resultant quality of life issues. Fyi for anyone considering the medication route, I would request that my cats’ prescriptions be faxed to my local (human) pharmacy, with refills, as almost all vetrinary meds are also used for people (my sister who recently had a kidney transplant was on Methimazole for years prior to her surgery, and we used to joke about her and my cat being on the same med, albeit at very different dosages!) I have another cat who’s been on heart meds for 10 years, and I find this option to be much cheaper and more convenient than purchasing them from my vetrinarian.
    About a year ago my cat Madeline was diagnosed with the same disease. She was then 13. She’s also sweet but super squirmy when it comes to meds, and the thought of having to pill her twice a day for (hopefully) 7+ years, and paying for twice daily visits from my cat sitter when traveling, was not appealing or cost-effective when compared to the ease and effectiveness of having her recieve one radioactive injection with a 98% cure rate, so I opted this time for option B. I’m in MA and the special clinic I took her to was very nice, with a seperate room for the cats receiving radiation therapy and their own “nurse” to care for them during their 3 night stay. Yes, it was pricey, the treatment and boarding was $1400, and I probably spent another $1,000 on vet bills (Maddie also had a heart murmer so the radiation clinic required an echocardiogram and chest x-rays before agreeing to treat her). It’s definitely weird to have to keep 2 weeks worth of radioactive cat litter in covered bins for 3 months before being legally allowed to send it to a landfill..I made sure to tell my sister about that stipulation just in case I died in a freak accident and the authorities discovered the 4 large utility buckets from Home Depot filled with litter and labeled me a Crazy Cat Lady, lol. But when all was said and done (and I survived the waiting period and thankfully disposed of the now non-radioactive litter), I am happy to report that Madeline is 100% improved, with completely normal thyroid levels. She is eating normally and back to her happy, sweet, non-manic self. No more night yowling, muscle wasting, or sprinting up and down the stairs at all hours. Just a content middle aged kitty who plays, sleeps, and eats appropriately for her age. Oh, and that I don’t have to pill twice a day for the forseeable future. The treatment worked so well that I will definitely do it again for yet another cat who ALSO is exhibiting classic hyperthyroid symptoms..Kali is 15.5 and is going to the vet tomorrow for bloodwork and examination. I’m praying it is Hyperthyroidism because it is uniquely easy to treat, unlike diabetes, cancer, etc. And I’m noticing that my 15-17 year old male kitty Marius (the one on the heart meds, another rescue if unknown age) is seeming awfully hungry and thirsty latley, so I might just be calling the radiation clinic and inquiring about a quantity discount. Oh, and clearing much more space in my basement for all my hoarded bins of used litter. Perhaps I am fated to become a Crazy Cat Lady after all….

    • Leigh says:

      I’m so glad to hear the treatment worked and your kitty is healthy again. I was wondering if you have ever heard of a cat being cured by the radioactive iodine therapy and then having the hyperthyroidism return?

  15. Manuela says:

    My Molly was adopted 6 years ago aged 6 and has always had the night time yowlies and a tendency to get fat. I never thought anything of it but 2 years ago finally managed to control her weight with a prescription diet food she liked. All was well until November when she had a bile vomiting diarrhoea and rapid weight loss episode. As she is difficult to crate despite being indoor, I took the opportunity to get a full blood screening.
    This showed up hyperthyroid and one erratic liver enzyime, high bilirubin. We rechecked as she didn’t present with classic hyperthyroid signs, but it was confirmed and thankfully bilirubin was back to normal. She wasn’t mega-hyper, 70 against a normal up to 50 T4, but as she is unpillable we decided immediately on radioiodine and diet control in the meantime. She has just had her radioiodine assessment. This showed up early signs of heart thickening so we know we’re doing the right thing, despite her blood pressue being normal and T4 count down to 30, showing the diet has really worked for her. She loves it and is a fat pudding again.
    Already the night yowling has diminished, the random hissing is all but gone, urine clumps are back to normal size, and she is much less highly strung. Nobody likes their cat to be away from home but it’s really no different to leaving them in the cattery for a holiday. Money is an issue but if we have to go without for her to have her health back, then so be it. £3000 by the time all the post treatment tests are completed!
    As far as the strictness of the diet and no treats – for cats that are more severely hyperthyroid (70 is not enormous) the diet needs to be strict, but we got away with tiny amounts of real meat treats, I mean less than 1g per day, absolutely no dairy and no manufactured cat treats. Fine for a temporary period like ours, probably not for lifetime management. Her radioiodine is at the end of this month … after that she will be back on her weight loss programme.

  16. Cary says:

    My 14 yr old cat has an appt today, I am insisting on a thyroid test. She had a complete blood count 4 months ago that was normal. I am almost positive she has hyperthyroidism. she has just about every classic symptom. However, she is only vomiting maybe twice a week, if even that much. I am very hesitant to give the medication now that I am reading about the severe side effects, especially the excessive vomiting, being that she doesn’t even have a problem with vomiting right now. I wouldn’t mind trying the prescription diet food, even though it is pricey, if it works I can deal with that. Has anyone had good luck with just the diet food alone? The radiation treatment is not going to be an option for me unfortunately.

  17. Michelle says:

    Hi my cat few months ago started to eat loads and was losing weight so at Xmas he was diagnosed with hyperthyroidism and started on medication but after 6 days he became very unwell, being sick and diarrhea and had to be hospitalised for 4 days, it then took probably a month to get him on a even keel again before started medication again, as vet said unlikely to be tablets that caused it, altho I thought it was too much of a coincidence not to be connected and true enough 6 days in again after starting meds he has gone down hill and vomiting again, so altho apparently very rare that cats can’t tolerate the tablets I obviously have that rare cat! His t4 levels are around 180 which I believe is super high, I am considering 2 options either the radiation treatment which there is a 4/5 month waiting list but my worry is what state will he be in by then what damage will have been done to his organs which will shorten his life and make the cost and stress of this treatment more of an issue or the dreaded alternative of euthanasia. Any advise greatly received.

  18. Mimi says:

    My 12 yr old Pumpkin was recently diagnosed with thyroid disease. We had him on Methimazole for 2 weeks before we took him off of it. During that 2 week period, he was throwing up constantly, no appetite, and very lethargic. He definitely wasn’t our sweet loving playful boy. He stayed totally away from his younger brothers. Within a week of stopping the meds, our sweet boy was back to his old self. no vomiting, playing, snuggling with his brothers. We are now giving him an herbal supplement, Pet Wellbeing Thyroid Support. Since it’s just a supplement, we know it will take awhile for it to start helping, but we are optimistic. We will still be taking him in to our vet every other month to have his blood checked. Honestly, we rather have Pumpkin be himself then be a loaf in a bed throwing up.

    Last year, our 22 yr old had thyroid disease. The vet put her on the methimazole. After 2 weeks she had the same symptoms as pumpkin, but also had a mini-stroke. Took her off the meds and within a week she was coming back to herself. Vet put her back on the meds in the fall, and she had another mini-stroke and never recovered from it. We had to say good bye to her in Oct. She didn’t have any mini-strokes, vomiting when not on the methimazole.

    Funny how they say that 10-15% of cats cant tolerate methimazole. We had 2 already and I’ve read a lot of comments/reviews on many sites where other cat owners are experiencing the same side-effects.

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