Saturday, May 21, 2011

Top 10 Signs of Hyperthyroidism in Cats

Hyperthyroidism is one of the most common endocrine conditions affecting cats, especially older cats over the age of 10 years. Some veterinarians estimate that about 5 to 10% of middle- to old-aged cats will develop hyperthyroidism, and, due to factors that may include environmental exposures, that number is on the rise.

Thyroid hormones normally regulate many of the body’s metabolic processes. As circulating levels of thyroid hormones rise higher and higher in cats with hyperthyroidism, a progressive increase in their metabolic rate develops: this leads to a multitude of changes throughout the entire body, including loss of weight and muscle wasting. High thyroid hormone concentrations also interact with and stimulate the central nervous system, which commonly leads to increased activity or restlessness, as well as other behavior problems.

Clinical signs associated with hyperthyroidism can be quite dramatic and cats can become seriously ill with this condition. Untreated, hyperthyroidism in cats can lead to heart or kidney failure and can be fatal.

However, this disorder is a very treatable disease and most hyperthyroid cats will make a complete recovery. I’d discuss the various treatment options, together with pros and cons of each form of treatment, later in this current series of posts I’m doing on feline hyperthyroidism.

Do You Know the Clinical Signs of Hyperthyroidism to Watch for in Your Cat?
Here I’ve listed the top 10 most common signs that cats with hyperthyroidism can develop, from most common to least frequent.

Your cat doesn’t need to have all of these clinical signs or symptoms in order to have an overactive thyroid problem. But if your cat has one or more of these signs, especially if he or she is older than 10 years of age, you should definitely have your cat tested for hyperthyroidism.

1. Weight loss
Weight loss despite a normal to increased appetite is the classic and most common sign of hyperthyroidism in cats. Hyperthyroidism is so common that it should always be considered as a possibility in any middle-aged to older cats that has lost weight, even in none of the other clinical features of the disease are present.

The weight loss associated is generally progressive and is usually first noticed by the owner as a loss of muscle mass around the cat’s back (spine).

With time, severe muscle wasting, emaciation, and death from starvation can occur if the cat’s hyperthyroidism is left untreated.

2. Increased appetite
The weight loss characteristic of cats with hyperthyroidism is typically associated with an increase in the cat’s appetite. This increase in appetite can be dramatic, with some cats doubling the amount of food eaten and frequently begging for food. Hyperthyroid cats eat more in an attempt to compensate for their higher-than-normal metabolic rate by increasing the number of calories ingested. Unfortunately, most cats cannot fully compensate and continue to loss weight even if they have a good to increased appetite.

Although most hyperthyroid cats have an increased appetite, some cats with mild hyperthyroidism will maintain a normal appetite, with no obvious change in amount of food consumed.

A few hyperthyroid cats will even develop a reduced appetite that is improved after treatment of their hyperthyroidism. Most of these cats with a poor appetite have a rare form of hyperthyroidism called “apathetic hyperthyroidism,” which is described in more detail below (see clinical sign Number 10).

3. Hyperactive, increased energy, or nervous behavior
Hyperactivity, exhibited particularly as nervousness or restlessness, is relatively common in cats with hyperthyroidism. In extreme hyperthyroidism, muscle tremor or twitching may be apparent, and affected cats are often described as having an anxious or frantic facial expression.

In some cats, especially in the earlier stages of their hyperthyroidism, their owner can misconstrue such increased activity and energy as a positive sign of health. One must remember that cats normally become quite sedentary as they age so this change of behavior leading to increased energy and activity is almost always a manifestation of an underlying disease processes.

Some of these behavior signs — especially restlessness or aggression — are often more noticeable to the examining veterinarian than to the cat owners themselves. Many hyperthyroid cats have an impaired tolerance for stress and do not wish to be held or restrained. Some will even develop a “panic attack” as a result of an impaired tolerance for examination or restraint during blood sampling. These cats may also develop panting, overt respiratory distress, weakness, and even collapse during these episodes.

To see a video of severe anxiety in a cat with severe untreated hyperthyroidism, see my previous blog post.

4. Increased thirst and urination
About half of cats with hyperthyroidism will show signs of increased thirst (polydipsia) and urination (polyuria). Veterinarians often refer to polyuria and polydipsia simply as “PU/PD.”

There are a number of possible reasons for the increase in thirst and urination seen in hyperthyroid cats. The most common explanation for the PU/PD is mild, concurrent kidney disease. About a third of all cats older than 12 years of age will develop kidney disease, so the finding of concomitant kidney disease in a hyperthyroid cat should not be surprising.

Two other causes for polyuria and polydipsia in cats with hyperthyroidism include the following:
  1. Increased kidney blood flow occurs secondary to hyperthyroidism, which can lead to what’s called “renal medullary washout.” This leads to the inability of the cat to concentration their urine normally.
  2. Compulsive water drinking secondary to a behavior problem may also occur in some cats with hyperthyroidism.
In both groups of these cats, the increased thirst and urination return to normal after treatment of the cat’s hyperthyroidism.

5. Vomiting or regurgitation
Gastrointestinal signs including intermittent vomiting or regurgitation are fairly common in cats with hyperthyroidism. Vomiting may result from a direct action of thyroid hormones on an area of the brain called the chemoreceptor trigger zone. In other cats, the vomiting can result from gastric stasis (e.g., delay emptying of the stomach).

Vomiting appears to be more common in cats from multi-cat households and usually occurs shortly after feeding. Therefore, vomiting and regurgitation in most hyperthyroid cats may simply be related to rapid overeating. In other words, these cats eats too much food too fast, overfill their stomach, and then vomit.

One solution to this problem during the early stages of treatment is too feed the cat smaller amounts of food more frequently (every 3 to 4 hours, if possible).

6. Anxiety, night yowling, confusion, aimless pacing
The behavioral sign most obvious to owners is night yowling (a long loud mournful cry). This yowling most often occurs in the middle of the night for no apparent reason, and generally causes the owner to awaken. Aimless pacing and easily interrupted sleep patterns may also occur in some hyperthyroid cats.

All of these behavior signs appear to reflect a state of confusion, anxiety, or restless associated with the increased central nervous stimulation caused by the hyperthyroidism.

7. Diarrhea, soft stools, voluminous stools
Soft stools and diarrhea can occur in about a third of cats with hyperthyroidism. Other cats develop large voluminous stools with frequent defecation.

It is likely that accelerated gastrointestinal transit contributes to the increased frequency of defecation, soft stools and diarrhea. Some of these cats also develop malabsorption, in which they do not normally absorb the food from the intestinal tract.

8. Fast respiratory rate, panting, difficulty breathing
Respiratory abnormalities, including a rapid respiratory rate, panting, or difficulty in breathing at rest, are also common. Respiratory signs tend to occur most frequently during periods of stress. However, some affected cats will be noticeably intolerant of heat and seek out cooler places to sit, and some (especially advanced cases) may pant or breath more rapidly in warm or hot home environments.

In the absence of heart failure, weakness of the respiratory muscles due to chronic hyperthyroidism is the most probable reasons for these signs. However, central nervous or psychogenic effects also play a major role in development of these respiratory signs, especially in states of stress.

When severely stressed, some cats with hyperthyroidism will develop severe respiratory distress, rapid breathing, and panting; in addition, these cats may eventually become extreme weak or even collapse from exhaustion and shortness of breath. Hyperthyroid cats should therefore be handled carefully and in the veterinary office.

9. Skin, hair coat, and nail changes
Unkempt, matted hair coat
Skin and hair coat changes often develop in hyperthyroid cats. The hair coat, especially in long-haired breeds, is often unkempt, dull, and may even be matted.

Some hyperthyroid cats can groom obsessively resulting in alopecia (baldness) or a miliary dermatitis (crusty rash, often with intense itching).  This is sometimes associated with an underlying skin allergy, but the skin problem is magnified by the cat’s apparent obsessive and compulsive behavior associated with increased licking and grooming.

Excessive nail growth may also occur, especially in cats with chronic and advanced hyperthyroidism. These nails appear thickened and may be more fragile that normal.

10. Apathetic hyperthyroidism
A small percentage (less than 5%) of hyperthyroid cats will show atypical signs where hyperexcitability or restlessness is replaced by depression, apathy, or weakness. Although weight loss is present in these cats, it is accompanied by poor appetite, instead of increased appetite. These disparate signs heighten the importance of clinicians having a high index of suspicion for such a common disease.

Many cats with apathetic hyperthyroidism will have concurrent severe non-thyroidal illness such as kidney failure, heart disease, or cancer. Therefore, it is wise to do a complete workup in these cats searching for secondary or concomitant disorders. Occasionally, however, no other medical problem can be identified and the cats respond completely to treatment of hyperthyroidism alone, with resolution of the depression and poor appetite.

In my next blog post on hyperthyroid, I’ll describe the 12 most common findings that your veterinarian may find when they perform a physical examination on a hyperthyroid cat.



267 comments:

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Dr. Mark E. Peterson said...

At 2 years of age, hyperthyroidism would be extremely unlikely. Only 5% of cats are younger than 10 years of age. If no weight loss, I'd forget about hyperthyroidism.

Unknown said...

My 16 year old cat has been vomiting for years. We switched her to grain free food ( when it became available) which helped some. She drank water like crazy, went through the house yowling, had loose stools (again contributed to food allergies). She was at one time 8 pounds but had dropped to 6.2. We recently moved and had to switch Vets. The new Vet did a complete blood work up as part of our initial visit. Everything came back normal, including the thyroid test. Vet suspects hyperthyroid even with a negative test. Fast forward 3 months and kitty isn't feeling so great, so we went back to the Vet. Kitty's heart rate is 240! Vet again mentions hyperthyroidism and we agree to start her on meds and see what happens. 1 week later, kitty goes back to Vet. She hasn't vomited once in a week, her heart rate is 160, she's gained to 6.4. The night yowling has greatly improved. Moral of the story, find a good Vet, and even if you gave negative test, don't rule it out.

Unknown said...

my female cat developed developed diarrhea with a rancid smell that would wake us up at night. She also started eating much more and begged for food most of the day. I took her to the vet and she said she has hyperthyroid and prescribed the med that I put in here ear. She also put her on an antibiotic for 7 days. The diarrhea did not stop but the rancid smell went away. She has been on the med for hyper T for a month now and her eating is slowly going back to normal and at her last visit she had gained 1 1/2 lbs in a month. The diarrhea has not gotten any better. She uses the liter box and jumps out without covering it. I go behind her and cover it up so the 2nd cat i have will use liter box. When it is filled without covered diarrhea the other cat i have uses my bath tub to do his business. Will her water like lite beige diarrhea go away after she is on the med for hyper T eventually? The vet said her colon was 3 times the size it should be but had not explanation why. Do you know of any other cats with this problem continuing on and never go away? Do you know why her intestines are 3 times wider than they should be. Hope you have some answers for me. Also she is around 10 years old.

Dr. Mark E. Peterson said...

2 year old cats do not develop hyperthyroidism.. too young!

Mara said...

My 3 year old cat has been on steroids/inhaler since March (slowly being weaned down). He had a major asthma attack and since he's been on the drugs, he's lost a bit of weight, though he's still eating normally. He's always had a healthy appetite though. Is the weight loss something normal that happens with the drugs, or should I be worried that it might be his thyroid? He's a pretty calm cat, not really the type to be up and restless. I just worry because he's a little skinny, compared to his brother, who's built like a brick wall.

Dr. Mark E. Peterson said...

Nearly impossible for a 3-year old to be hyperthyroid. The disease starts around 10 yrs with an average age of 13 years.

Anonymous said...

My male cat of 17 years has recently been diagnosed with hyperthyroidism, based on blood results. He was normal, only 6+ months ago in his blood work, , but his classic symptoms of it have been concurrent over a year with gradual weight loss. He was placed on medication a week ago.
My question is, he seems to start purring and then cannot "shut off" his purr. He sounds like he has mucus collecting in his throat. The vet did notice this as well, and examined his lungs which were clear and no issues with his heart. He often has this happen lately, and then gags and swallows a lot and is relieved only if he coughs. Do you think the thyroid gland is getting so big it may be starting to block his airway? Will the medication correct this in reducing the size of it soon? How long does it take, if so?

Dr. Mark E. Peterson said...

Methimazole does NOT reduce the thyroid tumor size but that's very unlikely to be the problem.

What you describe is not a typically sign of hyperthyroidism and is most likely NOT related. Talk to you vet about how the medication works, how to monitor, and have them start to formulate a diagnostic plan if the gagging and coughing persists once euthyroidism is restored.

what_the_heck_in_Texas! said...

You are SO kind to spend your time answering all these questions! I am amazed at your generosity of spirit!

I'm in Texas & just recovering from chemotherapy, so radioiodine treatment terrifies me. My almost 14 year old girl can't take the med- she threw up constantly, but she has all the signs you've mentioned & the vet said her thyroid level was off the charts. She did say many cats cannot tolerate the drug.

Are you aware of a facility in the Dallas-Ft Worth area (we're in Plano) that boards them for radioiodine treatment & would it be a health risk to me after she'd come home? We love our girl, but she is skin & bones, her fur is starting to come out in large patches & the awful screaming wakes us most nights between 3 am- 5am. I know cats can hide their illness- she's still spunky, but I don't want her suffering.

Thank you!

Karen

Dr. Mark E. Peterson said...

It should not be a problem with you follow the post-radioiodine precautions. Talk to the facility to get mpre information and then call your physician to check with them.

Unknown said...

My cat is only 4 1/2, but exhibits most of the signs on here. I understand it's unusual in a cat this age, but his behaviors changed suddenly and he's begun wandering and yowling at night for no reason. Is it possible that hyperthyroid could contribute to spraying indoors, which started about the same time? He sprays huge volume of urine, not typical for behavioral type of spraying. He's been checked for kidney issues and everything was normal. Now, I want to ask for thyroid tests.

Dr. Mark E. Peterson said...

Easy to test for thyroid function in cats. Talk to your vet about getting it done.

Unknown said...

What a great Dr you are to advise all these worried cat parents. Thank you, I've just spent 2 hours reading all the comments. I wish I'd found this blog when my cat was seriously ill and misdiagnosed. Actually undiagnosed. I've never met a vet that has suggested a specialist. It's as if they feel, if they don't know what is wrong then nobody else will. The only helpful suggestion was from a receptionist that suggested a certain vet that specialized in cats and didn't see dogs... Anyway, thank you. I look forward to reading your other articles. I wanted to know your thoughts on dry food vs wet. I give mine dehydrated (rehydrated with water) raw food and one pouch of high grade wet food per day. From what I've read, dry food causes diabetes and my instinct tells me it's not good for them. Cats should surely eat as similarly a diet as possible to one they would in the wild, which would be fresh prey not dehydrated prey?

Dr. Mark E. Peterson said...

Thank you for your kind comments. I agree that cats should be fed a more natural diet. This is one with a higher protein/lower carb content with about 70% moisture. So a bit a dry is probably fine, but most of the diet should be canned (or raw).

Unknown said...

My cat has many of these sx, weight loss, licking hair alot, loss of hair, eating more than usual. BUT my problem is I took him into the Vet and they did tests $800 worth I might add. and found nothing! Can he be hyperthyroid and test negative for it?? Now I have found red urine on my dog's pee pad (small amount, might be cat?) and that does not seem to fall into the thyroid issue. Or does it?

bonnielou said...

My 14 year old cat is scheduled for Radiocat this coming Jan. 12th. He has had constipation issues for three years, managed fairly easily, but just had a severe bout, and may now be having a problem with megacolon. He was mostly blocked two days, over the New Year's Holiday, had two high enemas Sat., with slow results, but eventually lots of results, including a normal poop Monday evening. However, he again had trouble in the night, and had another enema this morning, and four pieces came out (they tend to get stuck in 'pouches' near the end of the colon, instead of coming out, especially if they got too big higher up in the colon. He may just be on a downward spiral, and this problem may not resolve. I don't know if it is crazy to still do the radiocat, not knowing how this will play out. My vet says go ahead, don't reschedule, as the hyperthyroidism is hard on all his systems. He is eating a mostly meat, canned diet, with added psyllium, sometimes also pumpkin, and plan to add miralax. Any thoughts?

Dr. Mark E. Peterson said...

Hyperthyroidism doesn't cause megacolon or constipation. So those signs are not going to be any better once you treat your cat. If Radiocat makes him hypothyroid, the constipation could worsen.

Dr. Mark E. Peterson said...

Yes it could be all due to hyperthyroidism... have you had her checked? Cats on methimazole commonly relapse and need doses adjusted as the tumor grows. Call your vet.

bonnielou said...

Thanks for your reply. My post Jan. 5th was unclear, and insufficient, I see. I just assumed that it would be understood that he was already deemed hyperthyroid before the constipation episode. The constipation has been a long-time issue, but this recent severe episode is new. He is scheduled for Radiocat for his hyperthyroid diagnosis (T-5)(Free T-4 is 57), and symptoms of weight loss and ravenous appetite. My concern was, that the constipation might not resolve, and would complicate his hospital stay for Radiocat. In the meantime, he got a prescription Friday for Lactulose, and is now finally much better, and we are no longer thinking that he might have megacolon. Radiocat studied all his records carefully, before accepting him for treatment. I do know that the two problems, constipation and hyperthyroidism are separate problems, just tied together in time. So I feel better about taking him in for the Radiocat treatment tomorrow. I am no longer in deep despair!

Unknown said...

My cat's hyperthyroidism is controlled with methimazole but she is still very thirsty all the time. Creatinine is 1.6. Could there be underlying kidney disease or problems with the thyroid even though T4 is 2.6. I am considering radioiodine tx.

Unknown said...

My cat has controlled hyperthyroidism with a T4 of 2.6 but she remains extremely thirsty and has mild hair loss and weight loss. Her creatinine is 1.6. Could this continue to be problems the thyroid or underlying kidney disease? I am considering the radioiodine tx.

Dr. Mark E. Peterson said...

Yes, very early or mild renal disease cannnot a;ways be diagnosed with a blood test. I'd consider running a complete urinalysis with culture to help define this better and rule out infection.

Kewpie said...

My hyperthyroid 12 yr old cat is presently waiting for her I-131 treatment, we take her next Monday. She is bringing up fur balls everyday (started about 4 days ago), she usually does this at 4.30am, she's not a particularly hairy moggy, classified as a short hair but she has some very long patches (she is a tortoise shell). Could the hyperthyroidism be the cause of so many fur balls? She doesn't seem to be excessively licking and cleaning herself. I'm in Australia and it's summer, so definitely notice hair shed. Thanks

Dr. Mark E. Peterson said...

This isn't a sign that I hear about very often. Hyperthyroid cats typically vomits more, especially after eating. They tend to shed more and have an unkept coat but they do not seem to have an increased rate of hairballs.

Unknown said...

I have a male cat and he is 11 years old. I noticed he was urinating more often and losing weight as well as vomiting. He was recently diagnosed with hyperthyroidism and he has to take Felimazole twice a day. After 2 weeks I noticed he was still vomiting although it was less but one day he just started to vomit and wouldn't stop. I took him to emerg and he was there for 3 days. They did a pancreatic test which was normal, thyroid levels were now normal due to the pills, and an ultrasound was done which showed inflammation of the upper GI tract but everything else was normal. He was given Prednisone and Famotidine for inflammation and stomach troubles. He seemed to be improving slightly but noticed his back legs were weak and he was walking slowly, pacing around, lethargic and staring off into space for long periods of time. I took him to my vet and he gave potassium pills thinking he needed electrolytes from all the vomiting. He is eating well and his urination is good. Five days later and he vomited 6 times late in the evening and is nauseous. After a multitude of tests and thousands of dollars I do not have an answer. Any ideas? I haven't slept well in over a week and it's tearing my heart out to watch him suffer.

Dr. Mark E. Peterson said...

Most likely, this is a adverse reaction to the methiimazole. I'd think about stopping the drug and if he gets better after a couple days and remains so for a couple of weeks, then I'd use another form of treatment.

Steven Wan said...

Dr. Peterson....My 15 year old cat has had a problem with her tongue for several weeks. She does not seem to be able to chew or swallow anything solid. She tries to bite and eat, but her tongue just squiggles all over and she ends up spitting the food out. She has been having some signs of hyperthyroidism for a number of months, and in fact, I just found out that her T4 is >10 on my vet's scale, and so it is above the highest level they record. I just started the topical ear Methimazole. My vet could not find a reason for the tongue problem and inability to swallow. Could it be that she has a thyroid adenoma(s) that is not palpable from the outside, but is pushing on the base of her tongue from the inside side, and causing this problem? If she can't start swallowing soon, she will starve to death. I have read so much, but no one has commented on any tongue or swallowing problems. Thank you very much ahead of time for any answer.

Dr. Mark E. Peterson said...

This inability to swallow is not related to hyperthyroidism or the thyroid tumor, unless the tumor is malignant and has metastasized. That said, I've never seen such a problem associated with thyroid carcinoma.

Someone needs to do a good oral exam (and maybe endoscopy) under sedation to figure out what the problem is. It could also be neurological. Talk to your vet about a possible referral.

Unknown said...

My cat gained weight...he was always a big boy...18pds!!! And he was diagnosed with hyperthyroidism in Jan 2016...had a bad reaction to the meds and stopped eating and through not eating developed hepatic Lipidosis (fatty liver disease) and had a feeding tube for over a month, just got it out last week actually!! He's doing better not not 100% by far yet and I'm thinking of doing the iodine treatment for him next since the meds didn't work...but sorry yes over weight cats can have hyperthyroidism

Jamie said...

My 8 year old cat has had chronic diarrhea for the last few months and has started vomiting at least once a week. He had blood work and thyroid testing but they can't find anything. He's sleeping and drinking more too, do you have any suggestions? I'm not sure where to go from here.

Dr. Mark E. Peterson said...

Your cat needs a GI workup. Ask for a referral for an abdominal ultrasound and possible intestinal biopsy.

Unknown said...

Hi, I have a 5/6 year old cat and he just started to meow a little more than usual he seems to want something but I have offer him just about anything and his being a little fuzzy, I noticed he has been taking about 4 trios to the water bowl he uses the box probably twice a day his been picky about eating he has gained some weight and for the first time he tried to drink water from my glass all of this sudden behavior changes are worrying me alot, this just started a few days, should I be concerned? Or could he just be stressed?

Unknown said...

Hi Dr Peterson, my foster cat (approx age 10, real age is unknown as he was a stray) was just diagnosed as having hyperthyroid. Due to the vet that did his blood work not actually checking it until now (2.5mths later) treatment was delayed. He has stage 1 CKD. We had been feeding him a low protein diet due to the kidney disease (he was symptomatic which we now know as being the hyperthyroid), but have since switched him to a sr food. I was wondering if there is any way to determine how high the kidney values will be raised once we get his thyroid levels back to normal. If it's any help, his SDMA was at 18. BUN and creatinine were within normal range. Urine came back perfect.
Thanks!
If this question has been answered on a previous post, I do apologize.

Dr. Mark E. Peterson said...

We don't usually put cats with mild CKD on a low protein diet, especially with serum creatinine values <1.8. I do not really believe that you can diagnose CKD based on a SDMA value, at least in a cat with hyperthyroidism and is BUN and creatinine are normal and urine is concentrated.

The only way to tell how if CKD is present is to lower the T4 to mid-normal (not too low) and recheck the creatinine. T

Lou said...

My 15 y/o cat just had I-131 yesterday at Penn. He has a lot of anxiety at the vet's office and my local vet felt that he would probably need sedation. None of the local radio cat facilities would treat him because of age, anxiety, and the need for sedation. He is doing fine and will be coming home on Friday, after his radiation level comes down. I am very pleased with the care Spot has received at Penn.

M said...

I have a 16 year old male main coon. He was diagnosed a year ago with hyperthyroidism. The dr prescribed a food diet as a method which seems to be working and he has adjusted well. His bloodwork now shows that his levels are within normal limits. Around the same time of the hyperthyroid diagnosis he started to have thinning of fur around his neck and looked red. He got what looked to be like white crust in the same area. You could easily pull it off , almost flaky like. The dr prescribed an oral antibiotic and some ointment. After finishing the antibiotic it seemed to do the trick and looked like it was getting better but then reverted back shorty after. We went back to the dr and they again prescribed a similar treatment. I've read this is part of hyperthyroidism. But if his levels are supposedly good then should he still have this fur thinning / crust issue ? It doesn't seem to bother him and still has his normal personality. It seems to bother me more then him.

Dr. Mark E. Peterson said...

I've never heard or seen this reaction. I do not think it's from the hyperthyroidism but could be from the diet.

twisterp said...

Hi Dr. Peterson,
My 18.5 year old cat was diagnosed with hyperthyroid and high blood pressure about 10 days ago. He was circling and disoriented and experiencing vision loss. He was put on blood pressure medication amlodipine 1.25 once a day, and thyroid medication methimazole at 2.5 twice a day. The pill form of methimazole was making him vomit and lose his appetite, so he has been switched over to the transdermal form. His blood pressure was rechecked a few days ago and back in the normal range, and have been instructed to continue the medication. His first dose of the transdermal methimazole resulted in the same reaction as the pill, so I have am giving him half the dose and noticed an immediate improvement in regards to those side effects and his appetite is good. We've been instructed to return in two weeks to retest thyroid and kidney function....However he keeps having these odd spells of disorientation and what seems like total blindness, he paces and seems wobbly, especially in his back end but also his front legs...he still will do a little bit of circling but not like before, and also will be found stuck in corners and staring at the wall. When I hold his little body against me he relaxes but I have noticed occasional twitching in his right back leg or left front leg. Then when I put him down it is almost like he collapses for a little while. Yesterday he amazed me when he slowly and stiffly walked around the room playing with his light up ball (he has not shown interest in playing for many months) but just as suddenly he was back to the weird periods of checking out mentally, during which it seems like he doesn't notice anyone is there, he almost seems both deaf and blind. I have talked to the vet about this, and they seem a little puzzled and instruct me to continue the meds and things should return quickly to normal, but this pattern keeps going. Is there more going on than hyperthyroid that I should be concerned about, or is this a normal journey towards healing? Thank you in advance for your time. - Kaia and Mokes, the very sweet kitty.

Dr. Mark E. Peterson said...

It is unlikely that all of this is just the hyperthyroidism. I'd ask for a referral to a neurologist, especially if this continues for longer than a month after starting the medication.

Anonymous said...

Dr Peterson
Thank you for this wonderful page.

My 14.5 year old girl was diagnosed with hyperthyroid 3 months ago. I took her in because she dropped a lot of weight, had muscle wasting and just looked uncomfortable all the time. She also pulled at her fur in 1 spot for a few years now. We started with the Hills y/d food to see how that would go first. After 1 month her T4 dropped to normal range... but she lost another pound instead of gained....

In addition, she has never had inappropriate elimination issues- until she was on the Y/D food for 2 weeks! Since then (off and on the last 2 mos) she has had 2 episodes of straining/blood/urine outside the box and has had large fur balls several times a week. Her appetite is no loner ravenous and her numbers are in check but I am really worried about this urine issue/pain. The vet said her kidneys felt small and there were no signs of stones or anything. They thought it could be early CKD - but why only after the Y/D food?

So my question is --- have you heard of this food having this sort of affect or what could be the indirect cause? Also, is this how it is going to be for her now? Numerous episodes of painful urination.. if so I'd want to consider putting her to sleep instead of ongoing suffering of food she doesn't really like and recurring pain when she needs to go to the bathroom :(

Thank You!

Dr. Mark E. Peterson said...

No, I don't think this is related to the y/d. Talk to your vet.

Molly said...

My 11 year old cat has all of these symptoms but when I have brought him to the vet and had labs checked they come back normal. He continued to lose weight so I brought him back again a few months later and had them redo labs just to be sure and they are still normal. Everything else checks out completely healthy with no explanation as to why he is losing weight. Is it ever possible for labs to not show elevation for hyperthyroidism? The vets even said they could feel his thyroid gland was a little enlarged. Any thoughts? Thanks in advance!!

Dr. Mark E. Peterson said...

Very unusual to have normal T4 with many clinical signs. I'd recommend doing a full thyroid panel (T4, T3, free T4 and TSH) is not already done (I'd also submit to a different lab than the first one... make sure the vet is NOT using an in-house method). If you cat is hyperthyroid, then they will not all be normal. If you can, thyroid scintigraphy (scanning) is the most accurate diagnostic test and that could also be done.

Tiffany said...

My cat is on methimazole 5mg for his thyroid and has been on it for about a month now. But he has been drinking/peeing excessively and this wasn't a symptom before he was on the medication. I know it could be a sign of kidney disease among other things but if it was just due to his thyroid, does that mean he may need an increase in his medication? I have put a call in to the vet to make an appointment for a follow-up, I just wanted to put my mind at ease until then.

Dr. Mark E. Peterson said...

Unlikely to be related to the hyperthyroidism. See you vet and try to bring in a urine sample too.

Tiffany said...

Thank you for your prompt reply. I appreciate your expertise!

Unknown said...

Hi Dr. Peterson,
I have a female calico, Aurora, age 15 who was diagnosed Hyperthyroid Dec 2, 2016. She was losing weight, drinking more and peeing outside her box so I asked vet to check her liver, kidneys and thyroid. She was started on 5mg Methimazole twice daily. By day 2 she had horrible foul smelling diarrhea (she didn't have the runs before this medication) then by day 4 I found bright red blood in her stool. She has been in quarantine since Dec 2nd, as my other cats can stress her out. I called vet, as I was worried the dose was too high. She said continue the dose. By day 6 she was vomiting large water puddles with bile. Then by day 10 her diarrhea was DARK and VERY Bloody. And she refused to eat her dry food and the Feline A/D can food which she loves (I would give her a small amount of can A/D immediately after her pill). Yesterday Vet redid T-4 and said to cut meds down to 1/2 a pill (2.5) twice a day. She gave her an anti-nausea shot and sent home some Metronidazole 250mg (1/2 a pill daily) for the bloody diarrhea. Aurora will NOT eat at all now, she is sad, hiding in her condo and I found a large spot on her bedding that literally looked like dark blood clots (with small amount of stool). It is too late to call vet tonight, and so I liquefied the Feline A/D food and am force feeding her every 3 hours. As I don't want to give her both her thyroid and Metronidazole without her having some food in her belly. She fought at first but then seemed to relax and let me finish her feeding.
Is this a side effect of the Methimazole?? The horrible smelling very bloody diarrhea? I am very worried about her and can't afford the Radiation treatment as I have multiple rescue animals (I tend to keep the chronically ill ones, as most people don't want to adopt them, so my vet and med expenses are quite high all the time).I also do TNR with the ferals so I can't afford the 1,500 for radiation treatment.
Have you heard of this type of bleeding being a side effect of Methimazole??? I can't seem to find much online after days of scouring the web. People's cats mostly seem to have the itching and vomiting as side effects. I had another cat on this med for 4 years who passed this spring at age 19 and she never had the runs, much less super bloody runs from the medication.
Any information would be much appreciated. I am very worried about my poor girl. she even growled at me the other night as I went to pick her up. She NEVER growled at me before.
Thank you in advance. :)

Dr. Mark E. Peterson said...

I don't know if the diarrhea is due to the methimazole. Not a common side effect. I'd stop the medication for a couple of days. If it's due to the meds, then it should resolve.

If it does resolve, the put your cat back on the methimazole to see if the diarrhea recurrs to prove that this is due to the drug and not something else.

Tiffany said...

Just giving an update after taking my cat to his vet. He had his blood work done again and his thyroid was still very high. They increased his dosage and stated the excessive drinking/peeing was related to thyroid.

Jersey's owner said...

16 yr old male cat on transdermal methimazole creme applied 2x daily to inner ear for almost 2 yrs. His original symptoms of weight loss, vomiting and foul smelling loose stool were resolved. Blood work has been done every 6 months including T4 & chem profile for heart, kidney & liver enzymes. However, last few months he has pooped outside of his litter box on occasion, I thought he was being picky in that it was litter box change day. About 6 months ago, my adult daughter moved in with her 5yr old small dog. The cat & dog get along well. HOWEVER, I was blaming urination found in living room on the dog, and believe now it is the cat. Dog is away a few days & I just found urination in bedroom from last night. Could not have been the dog. Cat has never done this before even at 6 yrs when he had a renal blockage & required surgery. IF it is the cat it appears there is a spraying on the sides of furniture not just straight peeing. I am wondering if the methimazole is reaching the end of it being effective or renal issue or behavorial? I also believe besides just getting blood work, it might be time for a physical exam? Appreciate all the excellent replies & advice.

Dr. Mark E. Peterson said...

Yes, make an appointment for a recheck exam and bloods. That should be done at least every 6 months on the methimazole.

Fifi's Parent said...

My cat , aged 13 has been diagnosed with Hypothyroidism. She was throwing up a while before being diagnosed. Now she has been on meds (Methimazole 0.1ml in her ear one daily) for two weeks and still throwing up, if not more. Not sure what to do with her??? Could it be a gastrointestinal issue? Could the meds be making her feel nauseous and throw up more? Will this go away? I was hoping she would throw up less after treating her hypothyroidism. Getting very frustrated cleaning up vomit every day.

Dr. Mark E. Peterson said...

I'm assuming that your cat has hyperthyroidism, not hypo. You need to recheck with your vet. If the T4 has normalized, then the vomiting is not due to hyperthyroidism and is likely due to the methimazole itself.

Remember that hyperthyroidism is caused by a thyroid tumor and that this is about much more than vomiting. Talk to your vet.

TheAussieEDNurse said...

Hi doctor. Our cat was diagnosed with hyperthyroid (her levels were off the chart) she had weight loss despite increased appetite, irritability and increased affection. She has been on neomercazole 5mg BD now for 3 weeks. We are due back at the vet in a week. However we have noted she has really started pulling her fur out, is sleeping more and is definitely not as affectionate as she used to be: she was alot more affectionate before all this started. Do you think these are side effects of the medication or just her body adjusting to the decrease in thyroid levels? I'm assuming the vet will do her that's next week when we return. If be thyroid has started to normalise do we stick with the tablets or have her thyroid removed?

Dr. Mark E. Peterson said...

Sounds like a side effect. I'd see your vet sooner to discuss. Read my other posts about treatment options.

Michael said...

Hi Dr. Peterson,

My 4.5 year old cat recently had blood work completed for the first time. All results were normal with the exception of his T4 level, which was 3.0 mcg/dl (based on a 0.8-4.0 reference range).

He shows absolutely no clinical signs of hyperthyroidism.

Given his age and lack of clinical symptoms, do you think running further tests (e.g., Free-T4 by equilibrium dialysis) is necessary at this time? Thank you.

Dr. Mark E. Peterson said...

Based on the lack of signs, young age, and normal T4 value, I would test again in 5 years. Hyperthyroidism rarely occurs before 10 years of age.

natpat72 said...

Hi Dr Peter son, my 10 year old cat was diagnosed with hyperthyroidism 2 weeks ago. His fur was really matted and he lost a lot of weight. He's also started coughing/sneezing with tremors at the same time, is this related? I've started him on thyroid Gold drops and will move onto medication if the drops don't help. Thanks.

Dr. Mark E. Peterson said...

Coughing and sneezing are not related to hyperthyroidism. Tremors could if the condition is severe. Thyroid Gold drops have never worked, at least in moderate to severe cases, in my experience.

Anonymous said...

Hi Dr. Peterson,
Do you believe it's necessary for a cat to have a full battery of bloodwork when the only issue is she lost a little more than a pound since her last checkup two years ago? Vet insists this is sign of serious problem and is likely a thyroid issue. Tests advised: "thyroid profile," "blood profile major," "CBC & electrolytes."

There have been no changes in her health, behaviors, activity levels, eating/drinking habits, etc.
She's 10-11 yrs old, spayed female.

Dr. Mark E. Peterson said...

Yes, I think all of the recommended tests should be done annually in all cats older than 10 years of age. This is especially true in cats that are loosing weight, as your cat is.

Unknown said...

Hi Dr Petetson. My 12 year old cat was diagnosed with hyerthyroidism and an enlarged heart in May.she has been on medication since and has put on weight and is breathing normally again. This last week though she has been sick a fair few times so isn't eating great. She's normally off it for a day then starts eating again, which She did do, but has still been sick. She has missed her medication twice now with being sick and not eating on 2 days. Her stomach is empty and this morning the liquid that came up was pinky red in colour. Not bright red. Do you think she's best going back to the vets In case her medication isn't working the same? Could it be related to her illness? she is due a repeat blood test next month to check her levels. Thanks in advance

Dr. Mark E. Peterson said...

Probably from the medication. Recheck with your vet ASAP.

Unknown said...

My 13 year old neutered male cat has been loosing weight for the past couple of years. He has had two thyroid tests that were reported as normal, the last one within the last two months. He now clearly has all the signs and symptoms of hyperthyroidism including increased appetite, increased drinking, increased urination and stooling, weight loss of more than 5 pounds over 2 years, now weighs 6 pound. He is still very active and seeks my attention as normal but he has no muscle mass and is very thin and appears unkempt. All blood counts, chemistry panel, and urinalysis reported normal. Can you have false negative thyroid measurements?

Dr. Mark E. Peterson said...

False negative results are seen, but not with cats that have marked and chronic clinical signs. Talk to your vet and look for something else.

Leelee03 said...

My 15 year old cat has been diagnosed with hyperthyroidism and will be treated with pill radiation in a week and a half. He has been defecating outside of the litter box, diarrhea, for about 2 moths now. I'm pregnant and can't keep interacting with his feces. I'm looking for some hope that he will begin using his litter box appropriately once he has treatment. If not, I'll have to find him another home and that would devastate me. What is the likelihood he will stop defecating outside of the litter box once his hyperthyroidism is under control?

Dr. Mark E. Peterson said...

Defecating outside of the litter box could be due to hyperthyroidism, so that may resolve once he is treated.

If the diarrhea is severe, however, not all of those cats get better (assuming that the diarrhea and inappropriate defecation are related). We have no way to know if the diarrhea will improve or resolve until you treat him.

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