7 Things You Need to Know About Hyperthyroidism in Cats
You noticed that your senior cat’s fur has been looking pretty scruffy lately. He’s been eating like crazy, but he’s still losing weight. He’s suddenly acting hyper and crying in the night, and when you go to clean the litter box, it’s flooded with pee. You know something’s wrong, that it’s a health issue, so you take Fluffy to the vet. A blood test reveals that he has feline hyperthyroidism. So, what do you do about hyperthyroidism in cats?
First, you have to understand what you’re dealing with. Here are some questions and answers to get you started.
1. What are the thyroid glands?
Cats with hyperthyroidism tend to look pretty scruffy. Photography by Suphaksorn Thongwongboot / Shutterstock.
The thyroid glands are two tiny bits located on either side of your cat’s trachea (windpipe). Their job is to produce hormones that affect many of the body’s functions, but governing the rate at which your cat’s body burns energy is the most important when we’re discussing hyperthyroidism.
2. What goes wrong in feline hyperthyroidism?
A tumor grows on the thyroid glands and causes the body to produce too much thyroid hormone, which makes your cat’s body burn energy too quickly.
3. What are the symptoms of hyperthyroidism in cats?
Because your cat’s body is burning energy too quickly, the first thing you’ll probably notice is that your cat is always hungry and is losing weight in spite of his massive food consumption. He’ll also be drinking and urinating too much. Hyperthyroidism can produce behavior changes such as increased activity and restlessness, and sometimes even aggressiveness. Your cat’s fur will start looking greasy and unkempt.
4. How is hyperthyroidism in cats diagnosed?
Your vet will perform a blood test that measures the levels of thyroid hormones in your cat’s blood. If the levels of those hormones are high, your cat is hyperthyroid.
5. What treatments are available for feline hyperthyroidism?
There are three common forms of treatment for hyperthyroidism in cats: medication, radioactive iodine therapy and surgery. All three have risks and benefits.
- Medication — typically methimazole (Tapazole) here in the United States — decreases the level of thyroid hormone in your cat’s blood. It is available as a pill or in the form of a gel, which is applied to your cat’s skin. Most cats tolerate methimazole pretty well. Medication seems like the least expensive option, but in the long run the costs can add up.
- Radioactive iodine (I-131) therapy is considered the gold standard of treatment, but you may have trouble finding a clinic that offers it within a reasonable distance. It is pretty expensive, but the good news is that once the treatment is done, your cat’s hyperthyroidism is cured.
- Surgery to remove the thyroid gland is an option, but it may not solve the problem. There may be tumor cells in other parts of your cat’s body that continue to overproduce thyroid hormone, or removal of the gland could mean he’ll no longer produce enough thyroid hormone and will have to be on medicine for the rest of his life.
6. What about prescription food for hyperthyroid cats?
This food is designed to be too low in iodine, a chemical that helps the thyroid glands produce hormones. It’s being heavily marketed to vets and cat lovers, but among the vets I know, there’s a good deal of controversy about whether it has been adequately studied and what effects the lack of iodine might have on a cat’s overall health.
7. What are the complications of hyperthyroidism in cats?
Feline hyperthyroidism can disguise other conditions like kidney disease, because “running too hot” improves kidney function. Some other possible complications include high blood pressure, heart problems and difficulty breathing.
Hyperthyroidism in cats is a disease that can be managed, but it requires commitment on your part and good communication between you and your veterinarian.
Do you have a cat with hyperthyroidism? Which treatments have you tried, and how did they work out for you? Are there support groups you’d recommend? Please share your experiences in the comments.
Thumbnail: Photography by John E Heintz Jr. / Shutterstock.
Dealing with hyperthyroidism yourself? Here’s some advice on how to manage hyperthyroidism in humans >>
About JaneA Kelley: Punk-rock cat mom, science nerd, animal shelter volunteer, and all-around geek with a passion for bad puns, intelligent conversation, and role-play adventure games. She gratefully and gracefully accepts her status as chief cat slave for her family of feline bloggers, who have been writing their cat advice column, Paws and Effect, since 2003. JaneA dreams of making a great living out of her love for cats.
Read more about cat health care on Catster.com:
65 comments on “7 Things You Need to Know About Hyperthyroidism in Cats”
this is… it’s just tough to see an article on this… only a few months after my cat’s death… from hyperthyroidism. radioactive treatment… my parents never knew a thing about this to the day abigail died.
you just HAD to post it AFTER my cat’s death, didn’t you?
We tried the gel on Perry’s ears and he was sensitive to it: his ears got burned. Poor guy. He had trouble with the oral meds. While we were saving up for the radioactive I procedure, he died from complications from a stroke (possibly related to his HT) or brain tumor. Still heartbroken 18 months later. I found dealing with a hyperthyroid cat more difficult than a diabetic cat (Mollie).
My cat Dante (12) was diagnosed with hyperthyroidism. We brought him in because he started urinating outside of the box. He has always been a super awesome cat and never had any kind of behavioral problems. Now he is on the medicine you put on the tip of the ear and still urinated outside of the box. We got a black light and found a ton of places he has gone. Cleaned them well and he seems to be going straight back to two spots consistently. We have put pee pads in those spots. Problem is he moved them around and is still getting urine on the carpet. Main thing is once treated should he still be urinating outside of the box? How long does he need to be on the meds before he goes back to normal?
Don’t crush the pills. They want them taken whole or they don’t work right.
My vet actually recommended crushing the pills with a mortar and pestle to ensure my Carmella consumed all the med. She’s 16 now and the symptoms are virtually gone. Just a little sneezing
We take CBD often, it does wonders for your general, stress, depression and even sleep.
Our cat was diagnosed with hyperthyroidism last year after we noticed him being more aggressive and loosing too much weight. Our vet put him on felimazole, half a pill in the morning and half in afternoon. It was great until we noticed that our cat is allergic to it. Skin lesions on ears to the point of bleeding, very itchy skin, especially the face, head and ears. Also the bottoms of the feet, that were very dark through his whole life, changed into a bright pink and were puffier than normal, also bleeding at times. Vet told us to take him off the medication and try the Hills food diet, which cleared the skin problem, but after 3 weeks of doing it, his levels are too high again. Vet said to try the food for few more weeks to see if the numbers go down…
I have an 18+ y.o.kitty who I have been treating with methimazole for over a year;her T4 values are good. She was dx with chronic renal failure in Jan. and altho her creatinine and other indicators are not very high yet I do want to begin feeding her foods with less P content. There are a lot of low P foods for her, but a lot of them are fish based. In your opinion, should I go with higher P content to avoid the fish or focus on keeping the P lower? And yes I have tried the prescription diets for her and she won’t eat them.
My almost 11 yo old female cat has always been an active cat, fun and funny, learned tricks and likes to play. She always was slim but lost weight slowly over the last few years. The vet diagnosed her with hyper thyroidism and prescribed medicine in treat form 1/2 pill in am and 1/2 in pm. She stopped eating and was not herself after 2 weeks. Checked her tyroid and it has come down to normal and vet decreased her meds to 1/3 or 1/4 treat 2 times a day. Now she decided she was not going to eat that. Her personality has changed completely. She is lethargic, hisses at her brother . I’m afraid to give the meds. What is a better option. Also, she is light orange and white and her ears seem very red and warm.
Hi Danna,
So sorry to hear you and your kitty are going through this! Please keep in touch with your vet to determine the best course of action. These articles might answer some of your questions, too:
https://www.catster.com/cat-health-care/how-to-get-your-cat-to-take-pills
https://www.catster.com/cat-health-care/lethargic-cat-or-cat-who-loves-to-sleep
https://www.catster.com/cat-behavior/cat-hissing-why-do-cats-hiss
https://www.catster.com/cat-food/what-to-do-when-your-cat-wont-eat
https://www.catster.com/cats-101/orange-tabby-cat-facts
https://www.catster.com/cat-health-care/my-cats-ears-are-hot-is-it-normal
My cat 15 yr old cat with hyperthyroidism was allergic to the prescription meds. Put him on Hills Y/D Thyroid food (ONLY ) thing he can eat. Has been on it approx. 8 weeks; after 4 weeks thyroid went from 11.2 to 2.9.
He is back to normal, with exception that he has noisy breathing, especially when sleeping. After the hyperthyroidism may have damaged heart? Does anyone have any experience with this?
Rae
How did you know he was allergic Rae? Out cat has become zombie like since on it. Depressed almost. We just took him to vet yesterday for bloodwork. I am so upset
I am a little worried. Satchmo is a Mainecoon I got as a baby at sixteen weeks old while I was living in South Africa. I now live in Canada for the last eight years. Satchmo is sixteen years of age, devotedly sleeps nect to me and is my shadow. I suppose with age he started struggling to maintain his usual muscular stocky self I thought, then his appetite became ferocious. No end to the quantities of food. His body fluctuated between his fuller youthful meaty self and a leaner scrawnier self. Seemed natural to me. But his personality changed over the last few months. Agressive at times toward the other cats. Started meowing endlessly at times. Became more restless. The loud meowing, new definitely has triggered my concern. Some brain fog and confusion. He also started sleeping so deeply that only a slight shake of his shoulder could wake him. He has been healthy all his life. As far as water consumption seems normal. Loo seems normal too. I somehow suspect it is hyperthyroidism. I fully intend to get the vet to come to my home and take a blood sample. Joyce said it worked very well for her ragdoll. Is this an emergency. Can I wait a week to ten days or is every day I wait a risk? Can you please let me know what you think?
Hi there,
Thanks for reaching out! Here is an article you might find helpful on cat meowing:
https://www.catster.com/lifestyle/cat-wont-stop-meowing-reasons-for-cat-meowing
Additionally, here is an article that talks about changes in cat’s eating habits:
https://www.catster.com/lifestyle/cat-behavior-tips-changes-eating-food-habits-mental-physical-health-problems
It is always encouraged to contact a vet as soon as possible if you are concerned about your cat’s behavior so a professional can examine your cat.
My beautiful tabby cat lost weight, ate lots of food and drank constantly. She was aggressive when I had food and was always trying to get into anything I had. She was also meowing a lot. She was diagnosed with hyperthyroidism and put on a low dose of methimazole. Within about 3 weeks, she was feeling better, slowly adding weight and seemed more content. About 10 weeks out, her personality has changed 100%. She wants to cuddle at night and is purring happily all the time. She loves the RX food and I am very pleased with the results.
Hi,
Treating my cat for thr same issue.
What kind of prescription food are you giving your fur baby?
I am taking my cat for a follow up and would like to feed him something different.
He’s always hungry.
The food I am giving isn’t enough.
Thanks!!!
Methimazole has helped my darling geriatric cat put on a little weight. She is sooooo much better since our vet diagnosed her.
As you all know, I want her to be happy and healthy!
Hard to believe she’s 16. ????
Methimazole has helped my darling geriatric cat put on a little weight. She is sooooo much better since our vet diagnosed her.
As you all know, I want her to be happy and healthy!
Hard to believe she’s 16. ????
We adopted tiny street cat 2 years ago , she was 10 years .
This week she start pee in bEd.
I took her to vet today and she was diagnosed with hyperthyroidism.
I am devastated .
She was homeless tiny cat and her level was 17 ., 2 years with us lever 43 .
We adopted her , feed her lots to gain weight .but she lost weight more then when she lived on street .
We have to figure what to do .
She is tiny 6 lbs , she is with us only 2 years and we love this tiny girl so much .
Devastating .
My Vet is great , I hope we figure best for our baby girl
Suddenly my 13, 6 month old male cat within 3 weeks has been diagnosed with hypothyroidism, now limb edema x 3, paraparesis, lethargic, alternating constipation & diarrhea, hyporexia, tachycardia, FIV.
Had an echocardiogram. Cardiology found no significant abnormalities.
What could be causing this? Should I have a neurology work up?
Hi there,
We suggest asking your vet for specific advice. Best of luck and hope your kitty feels better!
My 15-year-old was diagnosed and aside from weight loss and unkempt fu, he was doing well. I picked up his meds on my way out of town for a conference, came home, and he definitely was showing a behavior change, and he clearly had t eaten.
I couldn’t give him the first dose – he turned down cheese! (Normally you can’t keep him away!) I managed to get a half pill down his throat. If the meds are working, how long before I should expect to see him perk up?
Hi Jessica,
We suggest asking your vet this specific question. Best of luck!
My cat female 15 years old has been diagnosed and treated with methiazide for a couple of years. We went through any and every brand of cat food on market. Finally she just wouldn’t eat anything. We with advice of vet tried baby food. She only would eat beef and chicken. So far so good. 2 jars a day but I am worried about the taurine do I need to supplement.
You definitely should be supplementing with taurine, and probably other vitamins and minerals as well. There are supplements for cats available online and at some pet stores. I’d recommend an “easy complete” supplement for people who feed their cats a homemade raw diet, because it contains all the extra nutrients a cat would need that they might not get in, say, ground beef alone.
Hi Danny,
Can I check with you what baby food you fed your cat?
Many thanks,
Catherine
My cat, 13 years old, was diagnosed 2 months ago. By the time I was able to get her seen she had lost a lot of weight and was half bald. The pen the vet Rxd causes a weird neurological side effect. So I tried soft chews, which she ate for the first two wks. But because they’re the same flavor, she began to turn her nose up at it. My cat likes variety in everything except for her dry food, go figure.
So I tried a different topical. Not as bad of side effect as the pen but enough that I would only be willing to use it occasionally when I’m home and able to hold her.
Side note: I’m allergic to my cat so I can’t hold her for more than 5 minutes. The effects last about 15 minutes.
What will happen if I can’t get all the daily dosing into my cat that she’s been Rxd?
How long can I expect her to survive if she was both diagnosed late and doesn’t get her full meds?
I cannot afford the radioactive iodine therapy. And my sister said it didn’t work for her cat, so I’m not taking out a loan for something that might not work.
Hi Kellie,
So sorry to hear you’re dealing with this. Hope your cat feels better. We suggest continuing to stay in touch with a vet about this issue. If you’re having trouble with vet bills, these articles might help:
https://www.catster.com/cat-health-care/what-to-do-if-you-need-help-with-vet-bills
https://www.catster.com/cat-health-care/affordable-vet-care-for-your-cat
Our cat was diagnosed with Hyperthyroidism in July, we opted to try the medicine whilst we waited for an appointment for the Radiotherapy iodine treatment. Our cat was in isolation for 7 days and came home, she doesn’t appear to be eating as much as she once did but she is eating, I am not sure if it works that fast but it was well worth the cost. Medicine has an impact on a cats body that’s why we didn’t want her on it forever.
Both my cats are 12 years old and I’m worried about isolating them for so long. I know that the iodine therapy is less expensive in the long run but I’m worried about the psychological aspect on elderly , dependent lap cats. One of the two would not allow the ear cream. Did you have success with your treatment?
My Titan was diagnosed with hyperthyroidism at age 14. We give him half pill each morning. Had to crush up and put in yogurt. However has been a month and his appetite is still ravenous and urine is same or more. He is hungry all the time and it is just frustrating.
Any suggestions?
Hi Rosemary,
Sorry to hear that you’re experiencing this! We suggest contacting your vet with these questions.
Hi, Rosemary, I thought I was so clever grinding up the pill into their wet cat food, but when my vet heard that that was how I was getting the meds down, he shrieked – Pills are slow release and so have to be swallowed whole or they are not effective! It’s such a stress trying to get them down, hidden in all sorts of treat food etc and they are so quick to become wise to all these tricks. Force feeding is not an option with my 2. Then the vet told me about the drops option – well, after 2 days, they manage to sniff it out in any food and just will not look at the stuff they’re usually crazy about if I’ve snuck it in. So I’m left with trying the gel – not sure if it’s available where we’re living (Italy) or the injection – again, if available here. But as a previous owner commented, My 2 are very much lap cats and needy for human contact, so 7 days in isolation for these 2 13/14 year olds is not looking like a good option either. I hope you have had better luck with yours.
Hi, I used to try and sneak the pills into food but found it not effective as shes always spit them out. My vet showed me how to give the pills and its effortless and so quick once you get used to it. I sit behind her with her sitting between my legs. I put her food in front of her ready and while she’s distracted by the food I gently lift her head back (almost stroking her chin as I do it so its a positive experience), put my finger in her mouth slowly til she opens and just drop the tablet straight down her throat. It took a few tries but now its so easy. The trick is to gently hold the head right back so theyre looking upwards and sort of drop it in. She doesnt love it but its so quick and once its gone down I show her dinner so she forgets. She also now knows once the tablets gone down its food time! :)
Our senior cat had all the symptoms – crying all night, huge pees, hungry and eating everything but losing weight fast. Dr said use diet to control, he was looking almost dead when we took him in so I was suspect that it would make a difference but we gave it a go. Science Diet prescription food only. No treats, no human food ever. He was a different cat in three weeks and a year and half later still ticking at 15! The diet is definitely worth a go!!
Oh thank you so much Amanda. I am currently going through this and I don’t have any money, am going to try this
Hi Ann, so glad to hear your kitty’s doing well. I’ve been playing with my cats methimazole dosage lately with vet supervision. In March or late April, 2018, had her t4 checked. It was slightly high at 5.2 so started giving 3 5mg a day. Well it was way too much as it lowered her to 1. She had been on 2 a day. So dropped her down to 1 1/2 pill in am then 1 in pm. Just this past week of may 14, she turned very lethargic so got tested to find out her t4 rose to 10. She was given appetite stimulant and told to give her 1 1/2 in am, 1 in pm but 2 days a week give an extra half tablet. Have you ever had trouble regulating your cat? Tomorrow may 20 will be first day with extra pill which I hope will work since she’s being very hyper and vocal right now!
Thank you for the article. My car Ebonezer was diagnosed so.o st 6 months ago with Feline Hyperthyroidism and was first prescribed 1 whole Methimozale 5 mg pill by mouth twice a day. He was very listless and would hardly eat. So, the vet changed him to 1/2 tablet twice a day. He got better and was back to normal for a few months. During a 6 week follow-up, he had more tests and all results were normal, except his Kidney level had elevated slightly. The vet suggested KD Hills Science food for him as a preventative measure. He barely tolerates it, I feed it to him sometimes just so he can get enough in him. Now, 2 months later, he is crying again, hungry a lot and drinking water, etc. My question…could his thyroid meds not be strong enough, should he be taking the whole pill again? Also, is the CBD oil really helpful with hyperthyroidism in cats? I know a vendor who sells it and was curious. Anyone with answers or who can help, I appreciate you in advance!
Ebonezer Mommy
I use Greenie’s pill pockets to give my cat her pills and so far it has worked beautifully. Sometimes the pill will fall out but I just put it in another one and then she takes it.
They are either salmon or chicken flavored and she loves them!
We have a 14 year old male cat – that is causing us sleep deprivation – he constantly wants food and to be let out of the cat flap (which is open 24/7) – he had part of his thyroid removed, 3 years ago – but this has not changed him at all !
He constantly eats (probably 4 times as much as a “normal” cat) – yet does not put any weight on / off – recently he has been drinking a lot as well
But blood tests have shown nothing wrong with him
What could it be ?
My Dixie was diagnosed April of last year. There is no way I can get a pill in her so the prescription diet is the option I chose as the cream for some reason isn’t available to me. It is working and I’ve got my healthy girl back! However, I am braced for the day the diet actually causes other problems, as there are so many crap ingriedients in it. Only one company is manufacturing it and there are no treats available either.
In the meantime, I am happy to just have a happy healthy kitty again!
I can’t get a pill in my cat either so I bought a pill crusher and when it is crushed it is like particles of fine salt…I add this to canned cat food and she eats it right up!
Our cat “Midnight” was a feral cat that turned into a loving house cat. He was diagnosed with hyperthyroidism in February 17. We opted for the removal of one thyroid that was damaged, the other was healthy. No further meds were ordered after the procedure in March. He died one month later. We estimated his age to be 12 when he died. He was with us for almost 7 years. He was a great cat!
My 11 year old cat had the radioactive iodine treatment. It worked very well. She is now hypo thyroid so must take thyroxin daily in pill form.
I have had four hyperthyroid cats. All went through the i-131 treatment. The years of not having to pill them, or apply medication twice daily was worth the cost to me.
Pros: Once done, the cats do not need to be medicated. One injection, a few days away from you, and getting accustomed to a flushable litter for a few weeks is all your cat has to endure.
Cons: Hard on the kidneys. Cost. You have to flush the cat’s waste for a few weeks.
High lab numbers in thyroid are hypothroid …..low numbers are hyperthyroid ! It’s the one that’s backward, up is down, down is up
Nope! Hyperthyroid is high numbers!
Hypo is low.
You’ve got it confused.
We use transdermal methimazole in alternating ears. We do a dose in the morning and evening every day. Works like a charm and our girl takes it like a champ. WAY better than trying to force a pill down her throat.. which would be nearly impossible with this cat. Feisty is an understatement. We also use CBD in the evenings to help her anxiety that has come with the disease. She’s fat and happy again… and so are we!
How do you administer the CBD oil so she will take it? Something I’m interested in trying.
My 15 yr old Cornish Rex has hyperthyroidism. He’s also had HCM since he was six, so fortunately he’s used to taking medication. He vomited with the pill so we’re using the transdermal ointment and he’s doing well for his age and condition. I just alternate ears and make sure to clean them every couple of days to prevent build-up. I also get medical gloves and cut off the fingers to use as finger cots when applying the medication.
My 15 yr old male cat had this. I had experience pilling another cat and didn’t want to alienate this one. I paid $1200 for the radiation treatment in 2007 and he was completely cured and lived for another 4 years. For me it was 100% worth it! If you can afford it I would highly recommend it!
Our 12 year old Princess has been recently diagnosed with Hyperthyroid. She now runs away from me every time I approach her as she thinks I’m gonna force a pill down her throat..that I do twice daily. Ugh.
My cat was recently diagnosed as well. We use a flavored (tuna) compounded pill that we get from the vet. It is probably a little more expensive (about $30/month) than the regular pills but is so easy! My cat thinks it is a treat and begs for it every time we go to the kitchen. Good luck with your kitty!
We get ours compounded also, chicken flavour. My cat will NOT take pills, she loves this, we are now calling it a ‘treat’ and she runs right over to lap it up. Altho she was not doing well on it in the beginning and we had to stop and tried the food.. which miss fussy pants refuses to eat, when she does eat it she throws it up. So now we are back on the meds but at a very low dose due to the scratching she was doing.
Hi, Gina, please, please could I have the name of this medicine? I have 2 cats needing meds and am so stressed out, having gone from pills to drops that they just won’t take – the fight is not worth it! I see many talk about crushing the pills into food, which I was doing until my vet said NO! The medicine is slow release and therefore must be swallowed whole. Thanks a lot for your advice. We once had to give antibiotics that the cat wolfed down – they smelt of yeast – and I just don’t understand why the companies cannot do the same for the hyperthyroidism pills.
Hi Debbie have you tried putting the pill in canned food? I found my Tiltie loves turkey baby food. I put the pill in small spoon full of baby food on top of her canned and she eats it up.
Try the soft chews if she liked treats and is a good eater.
Get the variety flavor if she likes variety.
Thanks so much for your article. My Ragdoll cat – Lola is quite old – over 18 years I think.
I am not sure as I am the third owner. I have her for well over 10 years. She developed
the problem about a year ago. Eating and losing weight, drinking all the time and crying all the time. With in 3 days on medication she was her old self – I could not believe it. She is back to her old ways – quite affectionate and purring when happy – what a change. And – she does not look her age.
What medication is she on please?
I am a bit confused. In humans, the cause of hyperthyroidism is NOT from a tumor. It is, I think, one of those idiopathic diseases where there is no known cause. Why would this be different in felines? I once had a cat who had this. Yes, she lost weight and ate and drank a lot. She was put on medication, and the problem got better. NO tumor was found. Please explain a bit more.