Old Cat Disease: My Cat Was Hyperthyroid
My cat is nearly sixteen and heading towards fat and comfortable, just as she's been for the first twelve years of her life. But for nearly three years, she was hungry and miserable and steadily losing weight, no matter how much I fed her.
My cat had hyperthyroidism, which is a very common disease in older cats, only rivaled by kidney failure and diabetes. Hyperthyroidism is, quite simply, the thyroid going into overdrive and growing too many cells (this can also be caused by cancer but very rarely). The thyroid then produces too much T-4 or thyroxine hormone, which tells the entire body to work faster. This basically means that the cat's metabolism starts working too fast to feed and it starts to starve.
It is curable.
There are a lot of articles out there about hyperthyroidism in cats, so I'm mostly going to tell you what happened with my cat, what her symptoms were and how she was treated. A lot of it is actually similar to the way human hyperthyroidism is treated, but it tends to work better in cats.
And my cat? She's now fat and content and shedding fur all over my bed again.
An update from four months later: The cat is now very happy and healthy, though she hasn't entirely regained muscle mass in her back legs. She eats about 300g of cat food a day, and spends a lot of time purring. Her teeth aren't ideal, but I've been feeding her a small amount of biscuits (now I'm not trying to just get as much proper food into her as possible) and her teeth have improved as a result. Overall? I stand by everything in this article, and we've had no further problems.
Symptoms, diagnosis and how the heck did my cat get so old?
The nasty thing about hyperthyroidism is that it can creep up slowly, and you just assume that 'oh, the cat's just getting old'. Because old cats can go downhill fast.
Moss has always been a healthy cat, barring being overweight (over 5 KG her whole adult life) and a minor flea allergy. She didn't go to the vet more than twice in twelve years (and once was to get spayed!). She was an adoptee from the SPCA as an adorably and incredibly friendly kitten.
When Moss was about twelve, I moved her to my new flat along with me; she wasn't very happy to start with, and ended up with flu (she had a bad habit of running off into the bushes and being too scared of the road to come back up to the house, so I had to go and find her every day and carry her home. When winter arrived, she ended up cold and wet and sick, so I had to shut in my room next to the heater. She was very pathetic!).
Well, she never really put weight back on after that, but it wasn't until a year or two later that she started losing weight. It was a steady decline and somewhat dramatic - just before it started I took her to the vet for a check up and she weighed in at a healthy 3 and a half KG and no problems. A few months later, she was rushed back for convulsions (probably rat poison) and she was down to 2.8 KG and her ribs were starting to show. At this point, the vet noticed her teeth were going bad but said she was too thin, and that they wouldn't take a cat for surgery that might have convulsions. Essentially, there was too high a risk that she just wouldn't wake up from the anaesthetic.
Well, I spent the next year assuming that I wasn't feeding her enough and that she was just getting old, and doing my best to keep her fed. But she kept getting thinner, and worse - for me - she started leaving presents around the house. Smelly poop presents.
Well, I noticed that she was constantly hungry, which seemed weird - so hungry that she actually ate an entire rat (she NEVER eats rats!), and she suddenly started losing weight very fast. And then I noticed that even though she rushed to her food bowl, she wandered away again after a minute and the other cat would eat it. So I spent a day following her around and discovered that all she did was lick pathetically at the food, and she wouldn't even bother with dry food - her teeth were inflamed, though I wasn't sure what the exact problem was at the time, as she wouldn't let me look.
And in two days, she lost so much weight that I was actually scared for her - I think she got down to about 1.5 KG. I got toss her up with one hand, and not even notice. It was far more weight than she should have lost for just missing a few meals.
I switched her to the canned meat - non casserole types, Chef brand - and she was able to mouth more of that, and I managed to get her up to about 2.3 KG by the time we visited the vet. Along with the teeth, which made eating difficult and very messy (she could only eat a little at a time, dribbled a lot, and would leak bits of food and drink out of her mouth for the next twenty minutes), she was not putting on much weight, despite eating an entire large 700g of cat food a day. She also had a small corneal ulcer (basically a hole in the cornea, usually from scratches).
Oh, and between the large number of tiny meals, and the hyperthyroidism, she became practically incontinent. I discovered that, among other things, canned fish can be very bad for cats and causes diarrhea, that hyperthyroid cats urinate excessively. It became quite sad, and I had to constantly watch her for the moment when she suddenly realised that she had to poop and tried to run for the door, or a corner, and then just gave up halfway there. It was the middle of a cold and wet winter and she was too thin and pathetic to throw outside all the time - it wouldn't have been so bad if she'd had a litter tray right next to her, but my flatmates (understandably) didn't want a litter tray in the living room. And then I discovered that she was vomiting a lot of her food straight back up again (yay, more cleaning!), so she was switched to very small meals whenever she asked. I was feeding her more than eight times a day at the end.
She became so thin that she lost all her muscle tissue, and couldn't balance on her back legs to wash her face. Between the drooling and the weakness, she mostly gave up on cleaning herself and ended up with a very dirty face, paws and front. I had to start cutting knots of fur out, and grooming her daily. She was obviously weak and miserable, but still friendly - while she'd happily curl up in a lap, she was wobbly, rarely purred and was nervous about being pushed around or headbutted (she loves headbutting people. She's nearly knocked me over a few times!).
While the weight loss and the increasing incontinence and loss of house training was steadily increasing over a year or two, it was only looking back that it was really obvious that hey, the cat is actually sick. It all became a lot more dramatic because of her teeth; either she just got too thin to cope anymore, or the thyroid became much more active. The 'really bad' period only lasted about a month or two.
Anyway, I took her to the vet, and I was pretty sure that she had hyperthyroidism and possibly kidney failure (the symptoms are annoyingly difficult to tell apart). I'd spent the previous fortnight researching all over the internet, learning things like a) my cat had pretty much every single symptom, but b) the symptoms were shared with other diseases and cat problems, and c) canned fish was bad, and dry food was worse, and d) hyperthyroid cats vomit because they actually feel sick and dizzy, as well as the several possible environmental chemicals that might be causing it.
The vet found that her heart rate was fast, her temperature was elevated, she was too thin (obviously), and was slightly dehydrated (using a pinch test of the skin) and then ran a bunch of tests. They came back twenty minutes later with thyroid hormone levels high enough to be out of the range they bother measuring for, and an instant diagnosis. I went home with neomercazole pills, an ointment for her eye to ward off infection, and a plan. I opted for an injection for her jaw, as it didn't cost much more than the pill option - especially as she was so thin! - and she was going to be miserable enough already with one set of pills being (maybe) forced through a sore mouth.
The inflammation of the mouth was sorted out by the injection and she started eating properly again. The pills... didn't really do much initially, but once we upped the dose, she started gaining weight rapidly. Once I and the vet were satisfied that she didn't have underlying kidney failure and that she became healthy while the thyroid was suppressed, I booked her in for radioiodine surgery, and took her off the pills again.
It's been a month since the injection, and she's due to go back for a check up this week or next, and she is heading back to fat, is very happy, purrs a lot and is generally healthy again. I estimate her weight at about 4KG, possibly more. Oh, and I'm finally starting to feed her a bit less, now that she's put all the weight back on!
She's also started shedding again. Apparently fat cats have more fur to lose.
Listen to the sound of a happy, healthy cat purring!
This is just a sound recording of my cat purring happily, a couple of months after being cured of hyperthyroidism. The photos in the slideshow are from various times over the last year or so.
Cats may have some or all of these symptoms, caused by increased thyroxine or T4 (thyroid hormone) levels
Your cat is over ten years old
Not exactly a symptom, but the vast majority of hyperthyroid cats are old. If your cat is still young, it may have some other problem - it may just be roundworm!
This may be slow and steady or incredibly dramatic, depending on just how much T-4 is being produced. It is caused by the metabolism going into overdrive and using up far more energy than normal. It's pretty much the definitive symptom and the main problem.
My cat was eating nearly twice as much as she used to. By the end, she was almost constantly eating, or waiting to poop and then going back to eat some more. I had to leave food in with her at night, or she became too hungry. Severely ill cats, or cats with other problems, may in fact have a LOSS of appetite.
Hyperactivity, progressing to weakness/listlessness
Cats may become restless, cranky, or outright hyperactive. I don't think my cat did, she generally just flopped down somewhere unless food was going in or out. She was less cuddly and seemed more miserable though. In the later stages she was much quieter, had lost significant muscle mass and was wobbly. Muscle tremors and an 'anaemic meow' are considered symptoms of advanced hyperthyroidism. She pretty much stopped purring, though she was still friendly.
Higher heart rate, panting and low grade fever
The higher metabolic rate can lead to a higher body temperature and heart rate. You can't really check this at home and may have to just wait for the vet. My cat's temperature wasn't taken, but she had an elevated heart rate.
Goiters (enlarged thyroid glands)
The thyroid glands actually increase in size and nodules may be able to be felt in the neck by the vet. My cat's glands were actually bi-lobed (joined together).
Vomiting and diarrhea
The fun part. Due to the increased levels of T-4, the cat's intestines will move food along faster, leading to diarrhea and much nastier, messier stools, and possibly difficulty holding it in. My cat's litter box (when I locked her in with it at night) had about four times the number of stools than when she was healthy. Vomiting is either because they are just eating too fast, or because they feel sick and is seen in about 50% of cats. Be aware that they may hide it fairly well until they get very sick - I discovered after the fact that my cat would often just walk around the corner and throw up in the bushes. This meant that she wasn't getting enough food.
Increased drinking and urination
The T-4 also causes the cat to become thirsty, which later leads to a lot more urine. There's not much you can do other than provide the cat with extra water (or lactose free milk) and watch out for the cat running for a corner.
Your cat may stop grooming themselves properly, out of weakness or disinterest, or being too busy worrying about food. Some cats may go to the other extreme and overgroom their coat until it is too thin. My cat ended up with dirty brown fur on her white paws and front, and knots throughout her fur. I had to cut them out, and the vet advised cleaning her with a damp cloth (luckily she improved and started washing again).
Some common sense steps to prepare and cope before visting the vet
Feed your cat
If your cat is constantly hungry and not gaining weight, and you don't think it is worms (which it probably isn't if your cat is old, and worming tablets are easy to give), then FEED THE CAT as much as it wants. It is not getting enough from the food, because it is moving through so fast, and its energy demands are higher because the metabolism is going crazy. Your cat IS starving. Even if you manage to maintain the current weight, it probably has some lost ground to recover.
Pay attention to symptoms
Keep a close eye on what your cat is doing and write it all down if there's a lot to keep track of. You should do this for two reasons. Firstly to identify what all the problems are in order to diagnose the cat (and it may have more than one problem). Secondly to manage the problems in the meantime, from feeding the cat extra food, to making sure it has access to a litter tray (and it may need better access as its condition worsens). If the cat is vomiting, it will need more food and smaller meals. If the cat isn't grooming properly, you may need to step in.
Do some research
You're probably already doing that, just by reading this page, but read around. There's a lot of information out there, as this is a pretty common problem. When reading, pay attention to the symptoms to look out for, the different kinds of treatments, cost, life expectancy, and the fact that not everyone agrees on the same things. This will help you understand what's going on, help the cat directly, and make you more informed when you walk into the vets and they spout something about thyroids and ear gel and special diets at you. My vets (I spoke to different ones at the same clinic each time) were very helpful and nice, but I would still have been completely lost without all the background reading I had been doing. It also means that you will not be so surprised when your cat is diagnosed, and you'll know what else might be the problem.
How can you treat your cat's hyperthyroidism and which is the best option?
There are several ways of managing your cat's thyroid, although most are just various ways of delivering the same medication. I'll give a quick overview and then discuss the two treatments I actually used with my cat.
Management of the Hyperthyroidism
Medication: the cheapest and safest option is pills. They suppress the thyroid hormones and are easily adjustable. I gave my cat pills for a month before pursuing the radioiodine route, and I'll discuss them more detail further down.
If the cat is very difficult to pill, there is a special ear paste (which hadn't quite arrived in New Zealand, but the vets were talking about it, and it has been used overseas). Both this and the diet option are much more expensive than the pills and make it harder to measure what the cat is actually absorbing.
Beta-blockers are a third option, and I don't know much about them. All they really do is manage the symptoms (e.g. lower the heart rate), rather than reducing thyroid hormone production.
Diet: The special diet option can either be a specifically designed range of food, or a home made low iodine diet, which supposedly side steps the entire thyroid issue. Neither of these options are cures, the special food costs a lot more and the home made diet may be too difficult to manage - and you may not be able to get your cat to eat either. But they are supposed to work well enough, so if you can't or don't want to give your cat pills, and can't or don't wish to pursue further treatment options, they are worth investigating.
There are a couple of links at the end about the store diet (Hill's Y/D) and putting together a home made low iodine diet.
Fixing the Hyperthyroidism
There are only two ways of curing hyperthyroidism. Surgery and a Radioiodine (I-131) injection. Surgery is not advised; it used to be the only option but is difficult and expensive and it is very likely that a small piece of thyroid tissue may be missed and will just continue the problem.
The radioiodine injection is an almost miraculously effective method, and highly recommended in almost all circumstances. I decided that this was the best option for my cat, and it was definitely successful (I haven't even taken her back for a check up yet and she's put on another kilogram and I'm feeding her less.)
Beware of Kidney Failure
Your cat may have underlying kidney failure that is masked by the hyperthyroidism. Tread carefully!
Both these and the Radio-iodine Injection are also used with people!
About the pills
The pills I gave my cat were called Neomercazole and the active ingredient is 5mg of Carbimazole. This is metabolised into the other available medication, Methimazole (Felimazole®) (note - I wasn't offered it, so availability may vary by country). Neomercazole is slightly less effective and needs to be given at a higher dosage, but is safer for long term use and has fewer side effects. It acts by directly suppressing the thyroid hormone production.
I noticed no side effects, and they are considered uncommon, but they do occur. They generally appear when the cat first starts taking the pills, and can often be managed or eliminated by reducing the dose and giving the cat a chance to adjust.
Side effects include phantom itching that can cause the cat to damage itself scratching, vomiting, lethargy and loss of appetite. (Actually, the last two are possible; the cat was already somewhat lethargic from general weakness and avoiding the cold weather, and the appetite loss may have been what I thought was the cat not liking the pills. But neither were significant enough to consider as problems, and both went away as the cat improved and/or adjusted to the medication).
Giving her the pills
Pilling a cat is always so much fun. Moss actually used to be fairly easy to pill - she's very easy going, and I get to keep trying until she stops spitting it out, but with her inflamed teeth there wasn't really a chance of dropping the pills straight down her throat. Luckily the neomercazole pills are very small and can be added to food.
She certainly didn't want to eat them initially, but she got used to them. At first, I hid them in her food, but she as she became less hungry, and her teeth improved, she became more careful about what she was eating. Then I moved on to crushing them and mixing it with her food.
I had better luck if I diluted the powder by mixing it into the entire serving, but if I wanted to make sure she was eating it, I'd feed her a small amount with the medicine first. Initially, she's just leave the food half eaten because she didn't like the taste, so giving her a smaller amount first meant that she'd devour it while she was too hungry to care. I had read that the pills were 'bitter' - I do think she could taste them, but she got used to the taste. By the end of the four weeks, she was happily eating her food complete with crushed pills.
Did the pills work?
While on half a tablet twice a day she gained about 500g, up to 2.8KG, but was still constantly hungry. After increasing her to two tablets a day, she became less ravenous and went from having daily accidents to have only one in the second week. She gained another 300g, up to 3.1 KG.
She was on each dose for two weeks, because it took about a week for the remaining hormone to work its way out of her system, and the difference in the second week was noticeable. After a month on the pills, I decided to book her in for the injection, and stopped the pills (her thyroid had to be fully active for best effect). In the two weeks up until the operation, she lost that 300 KG again and became noticeably worse (hunger, misery, weight loss and toilet training wise) in the second week.
Are the pills a good long term strategy?
They're pretty safe, and they're easy to adjust. It's better to start off too low in case of kidney failure or side effects (some cats have issues with phantom itching, for example), and even a half dose is better than none. They're cheaper than the other options, but you may be paying for pills for a long time - years. A cat will need them for the rest of its life (this also applies to the other 'management' options; the diet or alternative neomercazole medications).
You will also have to make regular vet visits until the dosage is figured out - every cat is different. In my case it was three visits (diagnosis, check up and increase, check up and deciding that was the right amount). Each visit cost me about NZ$300 (about US$250) because they had to redo all the tests each time.
Even after the dosage is decided on, cats change. You will still have to go back once or twice or five times a year (depending on the cat!) for as long as she is on the pills. The pills themselves are affordable, but they do add up - I paid about $17 for a week's worth.
The average yearly cost would be about NZ$700-1000. For perspective, the cost of the radio-iodine treatment was NZ$775 (not including visits and pills beforehand and a checkup after; that would bring it up to NZ$1500-2000, assuming that you do take her in for all check ups and everything is straightforward).
A very simple and effective procedure with complicated after care!
Did you ever dream of having a mutant cat? Did you wish your cat could turn large and green and strong when chased by dogs? Well, now you too can have a radioactive feline!
The Radio-iodine Injection is both incredibly simply and delightfully dramatic. It is a single injection of radioactive iodine, which is taken up by the thyroid (and only the thyroid). Concentrated there it kills off the excess cells, and voila! The cat is better.
The most complicated part of the procedure is the fact that the cat becomes radioactive. My vet could only take two cats at a time because there were limited facilities to keep them in for the week after the procedure.
Failures and Negatives
In the vast majority (around 95%) of cases it works without a problem. In the remaining cases it may simply not work, for an unknown reason (to the endless frustration of my vet) and will work perfectly the second time around. Alternatively, the cat may have had an inactive thyroid rather than two active ones, and it may then wake up and take over the business of causing problems.
In cats that it does work on, it may cause temporary hypothyroidism, with the thyroid activity dropping too low, but this is easily managed and usually rights itself within a few weeks. If the cat has renal (kidney) failure, then the consequences may be much more severe as the hyperthyroidism usually counteracts and masks the renal failure. It's not advised to procede with the injection until you are sure the cat doesn't have significant kidney problems.
So, the cat is radioactive. They will have to remain at the vets in isolation for a full week, after which they are usually safe to come home (with conditions). They are measured every day to ensure they are at a safe level when released. Anything you send with the cat, such as a toy or blanket, will be destroyed.
The cat will be fairly safe when it comes out but will remain slightly radioactive for another week (slowly decreasing, of course). If you do not pick the cat up, do not let it sleep on your bed, do not remain in close contact (i.e. within one metre) for more than a few minutes at a time and do not let it socialise too much with other animals, you will be fine.The cat itself won't live anywhere near long enough to see any after-effects from the radioactivity. If your cat is particularly friendly, you'll probably have to confine it. Most vets recommend it, at least for the first few days.
However you will have to manage the waste very carefully, as the radioactivity will be concentrated in the urine. This means that you may have to confine the cat with a litter tray and you will have to be paranoid about cleaning up after the cat. This means don't touch any stools or urine with your bare skin, scrub the living daylights out of anything that said waste touches, and you will have to dispose carefully of the waste and litter afterwards.
I suggest covering the litter tray with a large bin liner, so that you don't need to worry about reusing the tray and can easily empty all the litter in one go.
Don't underestimate the amount of mess an adult cat locked in a room can generate! You will have to clean it out every day - if you don't, the cat will decide the litter tray is too dirty and find a bit of floor to use instead.
You can a) get flushable litter or b) bag it in a rubbish bag and store it for two weeks and then dispose of it along with the normal rubbish. Don't just throw it in the garden!
Some regions have radioactivity detectors installed at the waste facilities, and in those places your vet will tell you to keep the waste at least two weeks. In other areas, you can get away with one week.
Keep an eye on your cat for the next couple of weeks - by the end of the second week after the injection you should be able to see the cat gaining weight. If you have any concerns, contact the vet immediately.
There will be one more appointment for the vet to measure the thyroid hormone levels and make sure everything worked as planned, and then - ideally - you will be slightly poorer, and the cat will be happy and healthy again. Until the next problem strikes!
What can you do to avoid having kidney failure take over as the new problem?
Okay, quick and terrible biology lesson:
- Kidneys are responsible for filtering. If they are failing, blood doesn't move through them properly and the cat gets very sick.
- However, hyperthyroidism increases the cat's metabolism, which includes raising the blood pressure. This means that blood can be pushed through the failing kidneys and mask the underlying failure.
- When you treat the hyperthyroidism and lower the blood pressure, the cat may suddenly 'get' kidney failure.
So what should you do?
Well, first, most vets are aware of this possibility and there are markers in the tests that they can look for. According to the vet I had, severe kidney failure is usually detectable even in hyperthyroid cats, and minor failure isn't enough to worry about as the cat will have a much better and longer life with minor kidney failure than it would with hyperthyroidism.
Secondly, if you give your cat the pills and slowly raise the amount until it reaches the 'right' dose, you should be able to catch increasing kidney failure as the thyroid is increasingly suppressed. So you can then balance the amount of medication against the kidney failure.
If you go ahead and have the radio-iodine injection, then it is too late to be careful of kidney failure. It is best to find out in advance, rather than have the cat lose the only protection it has. If you cat does have kidney failure, you will have to decide whether to go ahead with the injection or just try and manage both at once with pills or diet.
Resources about hyperthyroidism in cats
After her final checkup at the vets
A month after her injection I took her back to the vet (it should have been sooner but I was busy and it had obviously worked). She was completely healthy (barring slightly bad teeth - nowhere near as bad as they were when she couldn't eat properly though) and weighed 4.1 KG (compared to 2.9 KG when I picked her up after her radio-iodine injection).
For the first two or three weeks, she continued to eat a lot, but it actually did some good and she steadily gained weight. By the end of the third week, she at half as much food, only three meals a day (though she still tries her luck at a midnight meal she's not desperate for it) and, amazingly, takes up to five minutes to eat her food rather than inhaling it in thirty seconds. She has since plateaued out at a nice and healthy weight and is very happy.
She actually purrs again (and she purrs a lot, especially when someone talks to, touches or feed her!).
The only leftover problem is that her muscles haven't built up enough yet to compensate for her heavier weight, and she's unable to jump properly. It's both a hilarious and tragic sight watching her trying to pull herself up onto my bed, or get down again without actually jumping (she can jump, but her legs go out from under her when she lands!).