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:
35 comments on “7 Things You Need to Know About Hyperthyroidism in Cats”
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.
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.
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
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!
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 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.