Hello and thank you so much for choosing to watch this webinar, which it's all about treatment of feline hyperthyroidism. My name's Sarah Caney. I'm a UK based specialist in feline medicine.
And what I'm gonna talk about in this webinar is going to include steps that we might need to consider having confirmed that diagnosis and then move on to concentrate primarily on treatment. What are the different treatment options? How do they work?
What are the advantages and disadvantages we need to be aware of, any potential complications associated with treatment, and also whether managing multiple mobilities, morbidities rather causes us on any particular challenges. So firstly, having confirmed a diagnosis of feline hyperthyroidism, are there further tests that we need to do? Well, I've put some possibilities on this slide, with some rationale behind why we potentially might want to consider doing these tests.
But the reality is that actually, of all of these options, it's mainly the blood pressure assessment, which I would really strongly encourage you to do in all of your hyperthyroid cats. And that's simply because we know that systemic hypertension affects overall at least 50% of our elderly cats. And therefore, whether or not it is associated with the hyperthyroidism, it's something really important, I believe, to have on our.
To do list of diagnostic tests because we know that systemic hypertension, high blood pressure can cause, potentially life-threatening, clinical complications. So very much encourage you to do a blood pressure assessment in all of your hyperthyroid cats. Cardiac assessment, liver assessment, whilst whilst we know that hyperthyroidism can affect both of these organs, it's rarely necessary for us to do any further sorts of investigations.
So I would only typically do any sort of a cardiac workup in a patient that I was worried had congestive heart failure and actually needed management. Of it, or if I see on my lab results that the liver enzymes are extremely high, much higher than I would typically expect just due to hyperthyroidism, which usually causes only a mild or moderate increase in liver enzymes. But if the liver enzymes are very, very high, I might choose to do, an ultrasound of the liver, for example.
Otherwise, I generally I'm not going to pursue further, examination. And then lastly, I wanted to talk a little bit about urine culture because in the past, this is something that I have potentially recommended as part of our assessment of hyperthyroid cats because there have been a number of publications historically that have indicated, Cats with hyperthyroidism are more vulnerable to subclinical bacteria. So clinically asymptomatic, but potentially important bacterial infection of their urine.
However, there have been some more studies in, in the more recent past, that have, I think, helped to determine the answer to this, this question and as you can see, I've put a cross now next to urine culture. I don't think this is something that we need to do. The first paper really just to mention, in reference of the, the newer data is this one, which is looking at subclinical bacteria, in hyperthyroid cats and showed a lower prevalence than perhaps has been reported in the past, about 5.
Of our patients in this study had subclinical bacteria. But even more helpful was this study by Mark Peterson, which was a prospective cohort study. So he had hyperthyroid cats presented for radioactive iodine treatment, just under 400 of them, and 131 e thyroid cats presented for routine assessment.
And found firstly that that the prevalence of subclinical bacteria urea in the hyperthyroid cats was just over 4%, but also in the thyroid cats. So in other words, the same prevalence. So, from his perspective, fairly.
Study for us again to look at, there is no increased risk in hyperthyroid cats. So in the absence of low urinary tract signs, there isn't really any rationale for performing urine culture in this population of cats. So we can cross that off our to do list.
So let's move on to treatment of hyperthyroidism. And we've broadly got two options in terms of curative options and non-curative or reversible options. So as you can see, I've colour coded those on this slide.
The curative options, which I would say are the preferred long term option where at all possible, as shown in green, and that includes surgical thyroidectomy, removing. Abnormal thyroid tissue, or radioiodine, to, use that, that treatment to ablate that abnormal thyroid tissue versus the reversible noncurative options, which include anti-thyroid medication, which blocks production of thyroid hormones, or use of an iodine restricted food, hills wide. Which also, its mechanism of action results in lower levels of thyroid hormones, but these importantly, these non-curative options need to be given continuously and lifelong to remain effective for our patients.
And unfortunately, no treatment is perfect. So whilst, as I've already said, I would prefer for the long term, a potentially curative treatment option, so surgery or radioiodine, are my preference for the long term management of this condition. And indeed radioiodine, I am not unusual in a feline specialist in, in preferring this overall because it does have a very high success rate, about a 95% cure.
Side effects are, are pretty uncommon. But it's not perfect, even so, because it's, unfortunately not as readily available as we would like. And so it just is not possible for every patient and also quite expensive for, for many owners as well.
But all of the treatments do have advantages and disadvantages, which hopefully will become also more evident in the remainder of this presentation, as, as we talk through them individually. The main purpose of this slide is really just to say upfront, nothing is perfect, and, and the right treatment actually is going to vary according to the patient and the owner situation as well. Anti-thyroid medications are very popular.
Most of the licence preparations are in the form of thiamazole or methimazole, but Vidalta is a sustained release form of carbimazole, which is converted into thhimazole within the cat. And thhimazole blocks production of thyroid hormones. So it's one of these reversible symptomatic treatments, which typically very well tolerated and effective within 2 to 3 weeks.
Many of our patients will be thyroid. And, thimazole in particular is in, is available in a number of different formulations. You can see varying size tablets, but also liquid formulations of two different strengths as well.
So we have a range of choices open to our owners. And so as part of our initial discussions, whether they're using these short term pre-surgery or long term with our patient for whatever reason, it's important to firstly talk to our owners about the different choices available, whether they have any preferences, but also to explain how to administer. These preparations to the cats.
And really important where at all possible, that we advise our clients dose the cat with the treatment so that the correct cat in the house gets the correct dose of medication at the correct dosing frequency to ensure most appropriate management of their hyperthyroidism. Recently, I was involved in a study looking at carers' experience of giving medication to their cats at home, and this was a really large study. We have more than 2500 cat owners participate, and that wrote up the results in the Journal of feline medicine and Surgery.
And what we found was that some of the key findings were that, firstly, owners weren't always provided with information on how to administer treatment to their cats, and those that weren't really would have liked more information and more support. So that's something really we need to remind ourselves that every time we prescribe a medication, we need to ask our owners if they have had experience of that in the past and whether they do need any support. But secondly, we asked a lot about treatment choice, and, and many of these owners, almost all of these owners had had some experience of medication in their cats.
In general, owners first choice medication was liquids, but actually, almost a third of owners did choose tablets as their preferred first choice medication. So again, we, we need to Be careful not to prejudge what our owners might prefer and assume that everyone would like a liquid formulation, for example, rather than a tablet, because very clearly that was not the case. This chart summarises the 1st and 2nd choice medication formulations that our owners chose, and you can see that the liquids are the winner overall, more than 50%.
The owners said that was their first choice. Tablets, almost a third of owners said, was their first choice. And interestingly, the second choice is really spread across all of the categories, really.
So, it's not the case certainly that those owners that prefer a tablet as a first choice prefer a liquid as a second choice. It just is not that straightforward. An older paper, which I published in the Journal of feline medicine and Surgery, was looking specifically at owners of hyperthyroid caps and their experience of oral medication.
And that paper also showed that important to owners, were, firstly, that the appropriate dose of medication was chosen, rather than focusing on easy methods to give their cat medication. So 90% of owners agreed with this statement on the left about prescribing the most appropriate dose. Of medication to their cats.
Also, similar proportions said they were, or would be if needed, quite happy to give their cat a pill twice a day if that was needed to control its hyperthyroidism, and only 14.5% of owners said once a day medication was the most important aspect when choosing a medicine. So, I think just put this in really to remind us all to, you know, resist that temptation to prejudge, well, it's a hyperthyroid cat, you know, it's going to be difficult.
Let's perhaps go for a liquid because more owners find liquids easier. You know, maybe this is actually not a difficult cat to medicate, even though it has got hyperthyroidism. And indeed, in our study, we asked specifically about ease of medication, and, it was 12% of the cats that were rated as very difficult.
40% of the cats, on the other hand, were rated as very easy. So a real range of answers given here by these owners. So what do we know about these oral medications in terms of their advantages and disadvantages?
Well, the advantages include that these are products we all have in our clinics, so they're widely available, they do work, the cat can be managed at home. They're titratable, reversible, effective, generally very safe, and spread the cost of treatment over a long period. So therefore, I think many owners you know can afford this treatment as well.
So a lot of things that that make these very popular as probably the most frequently prescribed treatment option for hyperthyroidism in the UK currently. But they do have some disadvantages. Firstly, we need to give them continuously, until either the end of the cat's life or the cat has a curative treatment option.
And so compliance definitely can be a challenge in terms of remembering, let alone administering the treatment for, for the cats, and some cats can be difficult to medicate. There are costs associated with monitoring. Obviously, long term treatment can be expensive, depending on how long the cat lives.
Side effects also can be seen and whilst often these are transient and minor, just in the early stages of treatment, and particularly if you do start at a higher dose that those sort of side effects, the sort of inappetence, gastritis, vomiting. For example, are more likely if you, if you start at a higher dose, so I often will start at quite conservative doses of anti-thyroid medication, often 1.25 milligrammes of thiamazole twice a day, for example, because you can always increase the dose to effect and starting at a gentler dose and increasing it tends to be less frequently associated with side effects.
But there are some major side effects, which do necessitate withdrawal of treatment. And, we'll talk more about those in a moment, but, which we obviously need to be keeping an eye out for. Some cats as well just do not really respond adequately to this medication, and or over time we'll stop responding to the medication.
And there are concerns that long term use, when we talk about using these products for years and some of our patients may allow that underlying benign adenomatous hyperplastic tissue to transition into something a bit more malignant. And Mark Peterson has published some data to support that as well. So from a side effect perspective, just a little bit more information here, so that the major side effects, which are generally rare, less than 5% of cats would include persistent gastrointestinal signs, haematological abnormalities including thrombocytopenia, leukocytopenia.
Hepatopathy, this dermatitis, which I'm sure you will all have seen, often the head and neck intense pruritic dermatitis, and some other more serious side effects, including myasthenia, IMHA which are much less commonly seen, thankfully. And if we do see any of these major side effects, then typically we do, the only option we have is to withdraw therapy. There are some anecdotal reports of cats with dermatitis where if you switch to a different anti-thyroid medication, you, you may, if you like, get away with it.
But if it is a true Drug reaction, then it will happen with all of the preparations available. And certainly if you see any of those more serious haematological or hepatic side effects, you need to withdraw all of these anti-thyroid medications and look for an alternative way to treat your patients. So ideally we want to dose that cat with its medication to ensure that the correct cat in the house gets the correct dose of medication at the correct dosing frequency so that we have the best chance of stabilising their hypothyroidism.
But of course some owners will find dosing the cat difficult and dosing the food, is something that that may appear to be a bit easier. And certainly from a pharmacological perspective, there's no contraindication in terms of the, the medication is absorbed. When given in the food.
But the main issue really is certainty of, of that cat getting its medication, because, if you dose the food, there is that possibility that either that food's not eaten, ends up in the bin, or ends up in a different animal in the household. So, where possible, dose the cat. Monitoring cats, receiving anti-thyroid medication.
I would, book them in for 2 to 3 weeks on having started, their medication so that I can check how, how are things going from a compliance perspective. Is the owner needing any support there? How is the cat doing?
Has it gained any weight? How are the clinical Signs. And then ideally from a laboratory perspective, we want to see that the total T4 ideally settles in the lower half of the reference range, and that there is absence of side effects.
We want to look from a side effect perspective, ideally a full haematology and biochemistry. And most of those severe side effects I've mentioned, if they're going to happen, happen within the 1st 3 months. So that's the time really to be most vigilant about side effects.
Once our patient is stable, then, as long as we've not seen any signs. Side effects in those early stages, we can reduce the frequency of those checkups, really just to, perhaps every 3 or 4 months through the year to see how a patient is doing with perhaps twice a year, T4 haematology biochemistry checkups. Blood pressure checkups, ideally, at least twice a year as well in this population, this age group of cats as well, just because we know systemic hypertension is common in our older cats.
Does it matter when you sample the cat for T4 testing? Well, timing of sample, there are a couple of publications that have looked at it and it doesn't seem to be important, in cats receiving oral or transdermal medication. Perhaps the only challenge is those cats on a slightly unusual dosing frequency.
So Vidal to the sustained release carbimazole preparation does have a licence for every other day. Administration, so Q 48 hour administration. And, so that's, I would just say be consistent with your monitoring.
I tend to sample on the day of treatment. So when the, the levels of T4, you know, are going to be most vulnerable, if you like, to the, the drug wearing off, but be consistent in terms of when you assess your patient. Transdermal anti-thyroid medications have been used in cats, perhaps less frequently used now that we have both tablet and liquid preparations of Tiamazole that are authorised in the UK, but transdermal preparations of Tiamazole are very popular in North America.
It's not licenced other than, I believe, in New Zealand, where there is one product that has been licenced for use in cats with hyperthyroidism. It does work, but typically it takes longer to work, and typically you need a higher dose. So often double the dose that, that has been needed orally is needed when you're using the transdermal route.
So it is an option if you find you, you cannot succeed with oral medication, but it is not licenced and it would not be my first choice, even if it were licenced because it is less effective. Iodine restricted food hells widely is another reversible non-curative treatment option. And this works by limiting the amount of iodine available for incorporation into thyroid hormone, thyroid hormone T4.
4 iodine molecules. T3 contains 3 iodine molecules. So the mechanism of action is just by limiting the amount of iodine in the diet, that then it means that there is not enough, if you like, for the cat to overproduce the thyroid hormones.
And it does work again. So it's certainly a valid treatment option, but it tends to be slower than the oral management. So patients are usually you thyroid within 1 to 2 months rather than sooner.
It's designed to be given on its own, so no additional anti-thyroid medication. Indeed, that's contraindicated because there would be a risk of hypothyroidism. And it does appear to be safe, but the main disadvantages are that it doesn't always work as effectively as we would like it to, and it does absolutely require a 100% compliance.
So if the cat. Goes off eating at the neighbor's house every day, or if it is a really massive hunting cat hunts, you know, perhaps, you know, every day or every other day, that could be enough to unsettle its, management of hyperthyroidism. And of course, with these older cats as well, the other concern is, well, what if another therapeutic diet might be needed at a later stage in the cat's life?
How are we then going to manage the hyperthyroidism? So good candidates for the iodine and restricted food, Hills ID would be indoor only cats, single cat households, cats that are relatively free of other illness and have dedicated owners. And I would say short term stabilisation, you know, perfect for that.
Avoid all those drug associated potential for side effects. And this is, you know, potentially a very helpful option, pre-op or pre radioiodine treatment. Poor candidates might include multi-cat households just because this is not a food that is recommended for, cohabiting, healthy cats.
So it's not a food that, that, would be recommended to just blanket feed everyone in the house. Also, not ideal for situations where you have cats that have intercurrent chronic kidney disease either stage 3 or stage 4, for the Cat that does go outside, perhaps eats elsewhere, hunts elsewhere, and cats with severe hyperthyroidism, because it often does struggle to be fully effective. And also, lastly, I think long term stabilisation, just that successful compliance, it is quite a big ask, really, in terms of, using just a diet to manage that cat's hyperthyroidism.
People also worry that really this treatment doesn't, from, this indeed is a chart from some of the Hills literature some years ago, doesn't often actually bring the thyroid hormone levels down to the level that we would be aiming for if we were using anti-thyroid medications orally. So the T4 levels tend to stay in the upper half of the reference range rather than lower than that. So whether that's enough to resolve clinical signs, is has been debated, as well as, as I've already alluded to, if you do have multi-ca households, you know, is, is this, a diet that is safe for them to eat the current.
Suggestion has been that if there are the cats in the household that they should have access to normal non-iodine restricted food in addition to Hills YD if the Hills YD is available ad lib for another cat in the house. There are a few recent studies involving YD that have questioned really fully the efficacy of this. So for example, this first study, liver enzymes remained elevated, creatinine levels didn't improve.
We, we hope creatinine levels improve in our hyperthyroid cancers as a reflection of increased muscle mass. So the suggestion in this study that whilst the total T4 did decrease, hyperthyroidism was perhaps not adequately controlled. And in the lower snapshot from a clinical paper from vet medicine.
Just a very small number of hyperthyroid cats. 2 cats with the highest total T4 the hypothyroidism was not controlled. The remainder did respond, but some of these cats subsequently developed CKD and were withdrawn.
So overall, again, you know, some mixed results being shown there. And the RCVS knowledge summary that was published in 2019 had a similar feel to it. So some evidence that these diets can help, but not always effective, lack of compelling evidence to suggest that this resolves clinical signs in the long term.
So it is an option, but I think it's as with all of the treatments, you know, it has some challenges associated with it. Surgical thyroidectomy is probably not performed as frequently these days as as perhaps 20 years ago when we had far fewer options for medical management of hyperthyroidism. But I do think if you have a patient, particularly that is healthy in other respects and relatively young, shall we say, you know, the 1012, 14 year old hyperthyroid cat that hopefully has many more years of life in it, that a curative treatment option where.
Should be very much recommended to the owner because there is that possibility of complete cure associated with removal of that abnormal thyroid tissue. And this surgery, I'm told, is not particularly tricky. Obviously, it does involve anaesthesia of the patients, but, it is possible generally to, to get very good results with minimal side effect.
The main side effects are, damage to your removal of the parathyroid glands and hypocalcemia as a result of that. That's the most life threatening side effects certainly that we worry about. There are others that, that we also need to consider when doing this procedure, but there are also potential for great upside in terms of resolution of the hyperthyroidism.
Having said that, fairly recent paper that I think the Royal Vet College collated data on and published, looked at 81 cats that had had thyroidectomies from two clinics, and actually the long term results were relatively poor, as you can see sized on the. Right hand side at the top there are only 39% of cats were long term your thyroid post op. So, main issues are recurrence or persistence of hyperthyroidism, quite a significant chunk of cats where that is present.
And that may be because they've had a unilateral, thyroidectomy, and, the other lobe is affected, although having said that, sorry, these are, bilateral thyroidectomy. So I think, that should have been ruled out in this study, but the other option, which. Now is uppermost in my mind is ectopic thyroid tissue, which we know from some previous studies is relatively prevalent.
So, something to be considered or incomplete, obviously incomplete removal of that thyroid tissue. So apologies for slightly misleading you earlier on in that discussion. So certainly thyroidectomy, not without its particular issues as well, but I do think still it's something that is very much warrants discussion with owners in view of that possibility of it being a long term successful and curative treatment option.
Radioiodine tends to be the favourite, treatment suggestion in a perfect world by people like myself, because it does have a very high success rate. So generally about a 95% cure rate, and very few side effects, long term, persistent hypothyroidism probably being the main one, but that probably affects less than. 5 to 10% of our patients overall.
And indeed, in the long term, radioiodine can be very cost effective. If your patient is likely to live for 2 years or longer, then radioiodine will be a cheaper treatment option for the most part, based on today's prices. There is, we know, an interaction between the thyroids and kidneys.
And so I thought it'd be useful to just insert a little bit of discussion on this, to, wrap up proceedings, if you like. So chronic kidney disease we know is very common in the same age group of cats. It's the most common concurrent illness that we see.
10 to 15% of our hyperthyroid cats have preexisting kidney disease at the time of their diagnosis. And hyperthyroidism, we know also is damaging to the kidneys. So it increases renal blood flow.
We see glomerular hypertension and hyperfiltration that can cause proteinuria, it can cause damage to those glomerulli, loss of those glomerully. And so, ultimately, it can be quite harmful to the kidneys. But, often masks that damage that it's causing because that increased renal blood flow and increased glomerullar filtration rate.
Can make things appear to be working better. And that presents us with a lot of challenges when it comes to our hyperthyroid cats. So the first challenge is that it can make it harder for us to diagnose hyperthyroidism, because if we have concurrent, thyroid and kidney disease, we have, overlapping clinical signs for a start.
So both of these conditions can cause an increase in thirst and weight loss. There are some laboratory abnormalities that can be cancelled out. So hyperthyroidism, for example, typically causes erythrocytosis versus anaemia as a potential consequence of chronic kidney disease.
But more importantly, when it comes to actually trying to diagnose, the hyperthyroidism, in a patient with chronic kidney disease, we need to be aware of this phenomenon called sick you thyroidism, whereby Presence of illness suppresses T4 levels, and so the T4 levels can be normal, even though the cat does indeed have hyperthyroidism. So that can make it harder to diagnose hyperthyroidism, but also it can be hard to assess the severity or presence of chronic kidney disease in cats with hyperthyroidism. And that can be because the hyperthyroid state and weight loss can also lead to breakdown of muscle mass and loss of muscle means less creatinine turnover.
And so therefore, less creatinine to accumulate, even if our cat does have renal disease. So, things can appear to be more healthy than they are, if you like, on that basis. We'll talk a little bit about SDMA in a moment.
Both conditions that also can reduce urine specific gravity and both conditions can cause proteinuria, so that can make it harder to differentiate between renal disease and thyroid disease. SGMA definitely, I think does have some value, but it's not perfect. Again, Mark Peterson has done some work on this, looking at hyperthyroid cats and age matched healthy control cats and looked at the STM.
Levels in these cats on a pre-treatment assessment for the hyperthyroid cats and the age matched healthy control cats and then following these cats for a series of months, in the case of the hyperthyroid cats following treatment with radioactive iodine. And he looked specifically at the hyperthyroid cats that's Were not aotemic pre-treatment. And, found that 16% of them were azotemic post treatment and then looked back to see, well, what was useful to potentially predict development of that azotemia.
And the SDMA was high in a proportion of these cats. But as you can see, it has a very low sensitivity. So quite a few of the cats that had a normal SDMA did actually go on to develop azotemia post treatment.
But presence of azotemia was helpful because it did actually have a high specificity. So not many false positives. In other words, if the STMA is high pre-treatment, it's a, it's a good indicator.
That the cat is likely to have underlying renal disease. However, a normal SDMA does not rule out the possibility of renal complications. This open access paper by Jessica Quimby also looked at SDMA in cats with hyperthyroidism, and mining the IDEX database, which is obviously gigantic amounts of data there, and looking at utility of SDMA and felt.
SUMA was much more reliable indicator of renal function than creatinine, which is obviously influenced by muscle mass and therefore, creatinine levels will change as our hyperthyroid cat is stabilised, for example. So STMA is more helpful in just looking at renal function in these patients. And this paper as well also indicated that SDMA can have some, some value, although some discordancy.
So as with Mark Peterson, really it's not perfect, but an elevated SDMA pre-treatment of hyperthyroidism should be viewed as suspicious of underlying renal disease. So other challenges looking at kidneys and thyroids, well, if we have certainly severe renal disease in association with hyperthyroidism, then that can cause us some issues when we try and stabilise the hypothyroidism, because all of the treatments for hyperthyroidism. Are going to lead to a drop in glomerular filtration rate because the hyperthyroid state causes this increased renal blood flow and increased GFR and therefore, whatever treatment we use to correct the hyperthyroidism is going to lead to a drop in renal blood flow, drop in GFR, which can be as much as a 50% drop.
And in many cats, that's tolerated fine, that return to normality is absolutely fine. But of course, those cats that have a more severe renal disease, sometimes it's not well tolerated. And that can cause a clinical deterioration in their renal status and and a little bit of a crisis.
Fortunately for us, it does mainly cause issues in those cats with more severe renal disease. And in that situation, sometimes, particularly the RS stage 4 cats, we may find we can't optimally treat that kidney disease because the patient is just, sorry, we can't optimally treat that hyperthyroidism because that patient's renal disease is just too brittle. So my approach, firstly, is to always aim for optimal treatment of hyperthyroidism because the thyroid disease is so damaging to the kidneys.
So it's never desirable to leave our cat just a little bit hyperthyroid, where it's all possible, we want to treat that hyperthyroidism, get the total T4 in the lower half of the reference range. But we do want to warn owners about the possibility of unmasking or deterioration of renal disease. We do want to monitor our patients clinically and also biochemically.
And if we see renal complications, we may need to reduce the dose of anti-thyroid medication if they're receiving that, or consider alternative treatment options if the cat is, for example, on iodine restricted food and having clinical consequences associated with that. Most cases, it is possible to optimally stabilise their hyperthyroidism without destabilising their kidney disease. This is one example of just that, just a couple of slides about Millie, a very elderly cats diagnosed with hyperthyroidism one year before I became involved, stabilised on 2.5 milligrammes of Fazol once a day.
So, Normally we would use twice a day thimazole, but she did respond very well to that just once a day dose. Doing quite well from a body weight and T4 perspective, all looking good, but in more recent months had destabilised, lost a huge amount of weight. And also, as you can see, on repeat blood testing was firstly azotemic now, so the creatinine has shot up, but also the hyperthyroidism is not adequately controlled.
So we've got, you know, a double whammy of issues here. And initially, the referring that increased the dose of Tiamazole, so increased to 2.5 milligrammes of Thamazole twice a day.
But unfortunately, this is not well tolerated, both in the sense of T4 went a little bit too low, below the reference range, but also the renal status significantly worsened with that. So it really was not clinically tolerated. And she was a cat that ended up on actually a slightly unusual dosing regimen where she had 2.5 milligrammes of Thamazole in the morning, 1.25 milligrammes of Tiamazole in the evening, and that just seemed to be the sweet spot for her where she gained weight, her thyroid.
Disease was under control. Her teeth was actually just one animal per litre below the bottom of our reference range. So I decided to leave well alone.
It is, you know, pretty much, where I wanted it to be, but the renal disease was stable. And she, she did well for, quite a long time until her kidney disease ultimately deteriorated further and and life became tricky again. Lastly, just a couple of comorbidities to briefly mention.
So diabetes is one. I think often people worry about management of diabetes and hyperthyroidism when they look at the data sheets, because often it says for anti-thyroid medications, that there is a contraindication to using the anti-thyroid medications, and that's possibly because they often are sweetened preparations. Sugar-coated pills.
But from my perspective, there isn't a contraindication to using, thimazole, for example, in a cat with diabetes because that daily dose and that small amount of sugar is, is not going to really be something that is going to destabilise or interact with significance in management of the diabetes. So a little bit of, of reassurance, hopefully to you there. But also just to comment really on, in particular, fructosamine assessments.
Fructosamine is albumin complexed with glucose and typically reflects glycaemic levels over the preceding 1 to 3 weeks. But if you have a cat with uncontrolled hyperthyroidism, then, that does increase, albumin metabolism and Shorten the half life of albumin, which means that fructosamine levels will be reduced. And in a cat that has concurrent diabetes, that can be quite misleading because you might see what looks like a normal fructosamine, even though actually the diabetes is unstable.
The fructosamine is only normal because that hyperthyroid state is is resulting in that increased protein turnover, which means there's less time. For that albumin complex with the glucose, so less opportunity for fructosamine levels to increase. So just be aware of that.
Also be aware that once you stabilise your hyperthyroidism, your insulin requirements may, may decrease because there can be some glucose insulin resistance caused by the hyperthyroidism as well. So a little bit of a juggle a little bit of fine tuning may be needed. Arthritis, are there any particular issues?
Well, certainly severe arthritis that's very debilitating, that can be a factor that, causes this sick you thyroid phenomenon, suppresses T4 levels in a cat with hyperthyroidism. So be aware of that when it comes. To diagnosing hyperthyroidism.
But it is safe, certainly from a medication perspective to use, non-steroidal anti-inflammatories in cats that have concurrent hyperthyroidism. So from a therapeutic perspective, no, issues that you need to worry about there. What about iatrogenic hypothyroidism, overtreatment of hyperthyroidism?
Well, this is definitely something I think it's important to make you aware of, because we are recognising now that this is actually not a good thing at all. Work from the RVC has shown that patients With iatrogenic hypothyroidism are more likely to have renal complications and therefore a worse prognosis and survival time associated with with their disease. So we want to very much be on the case looking for this and managing it appropriately.
Unfortunately, it's not always that easy to spot. This is a lovely picture of a cat that's got pinal alopecia. You can see the black cats that The ears are actually bald, so that was pretty striking.
And that is a clinical sign that is associated with hypothyroidism, but they're rarely, in my experience, that dramatic. Clin clinical signs not that dissimilar to a hypothyroid dog. So, excuse me, lethargy, weight gain, hypothermia, severia, Zika.
Myxedema all reported in cats as well. The lab findings also quite non-specific, so not always that dramatic for us, but increased cholesterol, mild non-regenerative anaemia. So to confirm a diagnosis, the easiest thing to do is to actually send some blood for a TSH assay.
So this is, the assay that's actually optimised for dogs. So hence the little C there, K9 TSH assay. Nationwide specialist labs, for example, run this and typically what you'll find in a cat with hypothyroidism, that the TSH levels are very high, typically well above 1 gramme per mL, can be 3456 nanograms per mL.
In combination with that low T4. If that's not available to you, you can do a TRH or a TSH stimulation test. That's another option, but that is definitely a bit more of a palaver, and, not always well tolerated by the cats.
They often will will throw up when you administer that to them. So my preference is to do a T4 and TSH Issay. How do we manage these cases?
Well, if we have a cat that's receiving medical management of its thyroid disease, then of course, we can dose rate titrate. So we can adjust the dose, ideally so that the total T4 is in the bottom half of that reference range. If we should happen to see iatrogenic hypothyroidism in a cat receiving hills YD, then we need to withdraw the food, but I don't believe there are any confirmed cases of rogenic hypothyroidism in cats receiving this food.
As you'll remember, we talk mainly about the fact that cats receiving this management don't tend to have as low a T4 as we would ideally like. So certainly it's a possibility, we should be aware of it, but I think pretty rare. The other main situation, of course, that we need to be aware of it is those cats having curative treatment options.
And ideally, we should follow these patients post treatment, 1 in 3 months post treatment. I would, typically assess the patients. I would do a haematology, biochemistry, assess the total T4.
And if the total T4 is low, and in particular, if our patients are azotemic, I would want to check TSH levels. And if TSH is high, then supplement again, particularly in that azotemic cat. If the cat's not aotemic, Then I may monitor for the for a few months and just see if that hypothyroidism is persistent.
Often we'll have a little bit of a dip immediately post iodine or surgery, but within 3 months, things will have normalised, so the cat doesn't necessarily need long term supplementation. But if they do, it's similar to your hypothyroid dog using L thyroxine medication. Prognosis following treatment of hyperthyroidism is generally very good, but it does depend on the severity of the disease, so clinical signs, and it takes, you know, if they are severe, take longer to resolve the cardiac complications take longer to resolve if they've been present for a long time, but also if there are other associated comorbidities that will impact on prognosis as well, such as chronic kidney disease, for example.
But often excellent is hopefully shown in these before and after pictures, many owners will will find this, you know, not a bad old cat disease to have if that doesn't sound like too many contradictions. And certainly my recommendations were at all possible would be to for a curative treatment option if you can, but, if you can't to design a treatment plan that really works best for that cat and that owner, keep in good contact with them to hopefully have you the best treatment outcome that you possibly can. Some useful resources just to finish off with my website, vetprofessionals.com.
If you look on the helpful info tab, actually, there's an additional sub menu on there, which is a health blog. There is one on hyperthyroidism, but also the video tutorials I've got in the cat cafes, the cat. Owners, some webinars that are free to access on hyperthyroidism.
Also book, which has got the green cover on the right hand side is designed for owners. That's the print version. The electronic version has been updated to include some information on liquid preparations, hence the Tyro norm branded edition below.
And the blue veterinary bulletin is a frequently asked questions document, which is in the free download section of the helpful info session section of my website as well. The AFP guidelines for management of hyperthyroidism are also a useful resource and free to access just if you Google that. So hopefully you can, you can find all of those resources.
Thank you so much for choosing to access this webinar. I do hope that you've found it helpful. Thank you very much.