The hyperthyroid cat with normal bloods?

Re: The hyperthyroid cat with normal bloods?

Kate Richardson — Mon, 04 Feb 2013 13:42:22 GMT

[quote user="Jillian Hall"]

[quote user="Kate Richardson"]

How big was the thyroid? I routinely palpate the thyroid in any cat over 12 coming in for a routine visit such as a vaccine and it surprises me how ofetn I can palpate it (albeit small) in cats that are clinically healthy. In your case the possibilities are

How high was the ALT?

[/quote]

The Thyroid was " normal" hyperthyroid sized. I.e. not unusually large ringing alarm bells for carcinoma, and not so subtle that it could be WNL.

The ALT was 66.

Concurrent non-thyroid dz quite possible but didnt get the opportunity for further investigation.

[/quote]

ALT not that high I guess, but very variable with hyperthyroidism, although I usually find the level of ALT elevation is comparible to the degree of T4 elevation. So no further forward but will remain a mystery unfortunately!

Re: The hyperthyroid cat with normal bloods?

Kate Richardson — Mon, 04 Feb 2013 13:36:04 GMT

[quote user="robloxley"]

[quote user="Kate Richardson"] Interestingly, I don't recall many CHF/hyperthyroid cases developing ATE. What are your experiences?[/quote]

IME cats with cardiomyopathy that develop symptoms either go into CHF, or have a ATE, or suddenly die rather than doing more than one of these

[/quote]

Just to clarify, I do see thromboembolic disease in cats with primary cardiac disease quite a lot, but I don't feel I see thromboembolic disease in cats with secondary cardiac disease at anywhere near the same level. Just an observation.

Re: The hyperthyroid cat with normal bloods?

Jillian Hall — Mon, 04 Feb 2013 12:39:20 GMT

[quote user="Kate Richardson"]

How high was the ALT?

[/quote]

The Thyroid was " normal" hyperthyroid sized. I.e. not unusually large ringing alarm bells for carcinoma, and not so subtle that it could be WNL.

The ALT was 66.

Concurrent non-thyroid dz quite possible but didnt get the opportunity for further investigation.

Re: The hyperthyroid cat with normal bloods?

Rob Loxley — Sun, 03 Feb 2013 13:56:40 GMT

[quote user="Kate Richardson"] Interestingly, I don't recall many CHF/hyperthyroid cases developing ATE. What are your experiences?[/quote]

IME cats with cardiomyopathy that develop symptoms either go into CHF, or have a ATE, or suddenly die rather than doing more than one of these

Re: The hyperthyroid cat with normal bloods?

Thomas Johnson — Sun, 03 Feb 2013 09:29:57 GMT

Another slight tangent, I have been treating a diabetic cat that had been stable on Caninsulin for over 2 years, he then had a hypoglycaemic episode and on subsequent bloods was diagnosed as hyperthyroid, his thyroid stabilised quickly on Felimazole and his diabetes stabilised again on about half the previous dose of Caninsulin. Unfortunately 2 weeks later he developed pyelonephritis and became keotacidotic, and as the ketoacidosis was getting worse despite appropriate treatment he was euthanased.

Re: The hyperthyroid cat with normal bloods?

Kate Richardson — Sat, 02 Feb 2013 15:40:01 GMT

[quote user="robloxley"]We've had a number of cats presenting with both acute CHF and concurrent undiagnosed hyperthyroidism (with associated atriomegaly), but as above how can we know whether they had a component of primary HCM with thyrotoxicosis on top, or just thyrotoxic LV hypertrophy? They have tended to have obvious goitres and obviously elevated T4 despite their non-thyroidal (cardiac) disease.[/quote]

Impossible to know if they had primary cardiac disease I guess. I agree with Martin in that I suspect cardiac disease is a lot more prevalent than we recognise. If I see a cat in acute congestive heart failure where I suspect it is secondary to hyperthyroidism rather than primary, then I certainly feel they have a better prognosis than if due to primary cardiac disease, however thay can still go on to develop CHF in the future despite control of the hyperthyroidism.

[quote user="robloxley"]I'd pose the question - how many of your known and managed hyperthyroid cats develop symptoms of heart disease (CHF, ATE etc.)? The hyperthroid CHF cats I remember were all presented in CHF before a diagnosis of thyroid dx.[/quote]

The only treated hyperthyroids who have gone into congestive heart failure post diagnosis and management have been ones who presented initially with CHF and were subsequently diagnosed as hyperthyroid (but not every case). Or the poorly controlled hyperthyroids. So I feel that in a lot of cases the heart can remodel once the thyroid is stabilised and managed effectively but not all of them. But the time lapse between initial CHF and future development of CHF does seem to be significantly longer if the CHF is due to secondary cardiac disease rather than primary. Interestingly, I don't recall many CHF/hyperthyroid cases developing ATE. What are your experiences?

Re: The hyperthyroid cat with normal bloods?

Rob Loxley — Thu, 31 Jan 2013 17:56:54 GMT

[quote user="Martin Atkinson"]In theory cardiac disease related solely to hyperthyroidism should resolve with treatment and that should differentiate these but practice doesn't always follow theory.[/quote]

Went to a recent talk by John Bonagura who also said that in his experience treating the thyroid may or may not result in resolution of LV hypertrophy

Very hard to know, unless you've echo'd the cat prior to onset of hyperthyroid disease, and this cat has non-thyroidal illness masking the true degree of thyrotoxicosis.

[quote user="Kate Richardson"]Does anyone know how common LA enlargement is in cats with hyperthyroidism and how long it takes to develop and whether it is related to how high the T4 goes?[/quote]

We've had a number of cats presenting with both acute CHF and concurrent undiagnosed hyperthyroidism (with associated atriomegaly), but as above how can we know whether they had a component of primary HCM with thyrotoxicosis on top, or just thyrotoxic LV hypertrophy? They have tended to have obvious goitres and obviously elevated T4 despite their non-thyroidal (cardiac) disease.

[quote user="Kate Richardson"] I rarely/never echo my hyperthyroid cats unless they are showing signs of CHF[/quote]

Likewise, have only really echo'd them if cardiac abnormalities auscultated - especially if considering surgery. Should we be looking at biomarkers in such groups at increased risk...?

I'd pose the question - how many of your known and managed hyperthyroid cats develop symptoms of heart disease (CHF, ATE etc.)? The hyperthroid CHF cats I remember were all presented in CHF before a diagnosis of thyroid dx.

Re: The hyperthyroid cat with normal bloods?

Martin Atkinson — Thu, 31 Jan 2013 16:23:48 GMT

[quote user="Kate Richardson"]Not sure I have totally understood you Martin. Are you wondering if the weight loss could be partially due hyperthyroidism given there is a thyroid nodule? I don't know how well the diabetes is controlled (but I am guessing if you are managing it it is probably as good as could be) nor how advanced the renal disease is, but given the cat is severely anaemic, I would hazard a guess that the thyroid nodule is inactive and there are plenty of good explanations for the weight loss without adding another to the mix! Not that its impossible![/quote] I was but we will never know the answers to this quandary as the cat died last night, and is now already pushing up daisies. HCT was 13% owner didn't want a transfusion, tried a cocktail of EPO, B12, Iron and anabolic steroids but too little too late me thinks. Thanks for the faith in my management of the DM, it was a stable if challenging case that I inherited when the previous vet nearly killed it with 7iu insulin, this being a 3kg cat that I stabilised on 1iu bid!

[quote user="Kate Richardson"]So are this cats cardiac changes totally attributable to hyperthyroidism or did it have pre existing cardiac disease which has been exacerbated by hyperthyroidism? Does anyone know how common LA enlargement is in cats with hyperthyroidism and how long it takes to develop and whether it is related to how high the T4 goes? [/quote] Don't know the answer to these questions but I do suspect cardiac disease is a lot more prevalent in cats than is readily recognised in general practice and may therefore only be picked up when the cat comes in with something else so we don't know if it was pre-existing. In theory cardiac disease related solely to hyperthyroidism should resolve with treatment and that should differentiate these but practice doesn't always follow theory.

Re: The hyperthyroid cat with normal bloods?

Kate Richardson — Thu, 31 Jan 2013 10:37:30 GMT

[quote user="Martin Atkinson"]

[quote user="Kate Richardson"]concurrent disease causing suppression, however usually fairly obvious concurrent disease eg severe dental disease, congestive heart failure[/quote] I have a sarcopenic, severely anaemic old cat with diabetes and renal failure with a thyroid nodule and a low TT4. I presume this is euthyroid sick syndrome with thyroid function suppressed as it is no catabolic. Difficult to know how much the symptoms are caused by hyperthyroidsm and whether speculative treatment would make the renal function worse. Such dilemmas are sent to keep us on our toes.

[/quote]

Not sure I have totally understood you Martin. Are you wondering if the weight loss could be partially due hyperthyroidism given there is a thyroid nodule? I don't know how well the diabetes is controlled (but I am guessing if you are managing it it is probably as good as could be) nor how advanced the renal disease is, but given the cat is severely anaemic, I would hazard a guess that the thyroid nodule is inactive and there are plenty of good explanations for the weight loss without adding another to the mix! Not that its impossible!

I have another interesting one on the go just to continue the theme of hyperthyroids that don't read the book.

17yo FN Bengal, presented with oral pain attributable to its 2 remaining teeth. Fairly good condition, still eating ok, subtle weight loss (250g in 18 months), gallop rhythm, no palpable goitre. Tooth needs extracting, but bloods and heart checked prior to GA.

ALT high 209. T4 39. Meloxicam and amoxclav in mean time. 5 days later back for scan, cat much more comfortable. Echo- LA enlargment, mild LV hypertrophy. BP normal. T4 rechecked and now 53. With hindsight, owners report cat has been more vocal and asking for food more over the past year or so, so very likely this cat is hyperthyroid despite minimal weight loss (unless the records have wrongly recorded previous weight). However quite advanced cardiac changes for subtle clinical signs and T4 level (although appreciate it is likely higher than 53, as suspect concurrent dental problem caused suppression). No evidence of congestive heart failure. But still the clinical signs of hyperthyroidism are subtle and suggest a mildly elevated T4 level rather than a massive elevation. I also feel that the ALT level fits with a much higher T4 level so again would have expected more obvious clinical signs. Most cats I see with advanced cardiac changes have overt hyperthyroidism and present in congestive heart failure.

So are this cats cardiac changes totally attributable to hyperthyroidism or did it have pre existing cardiac disease which has been exacerbated by hyperthyroidism? Does anyone know how common LA enlargement is in cats with hyperthyroidism and how long it takes to develop and whether it is related to how high the T4 goes? I rarely/never echo my hyperthyroid cats unless they are showing signs of CHF.

I am impatient to know what this cats true T4 level really is!!!!!

Re: The hyperthyroid cat with normal bloods?

Martin Atkinson — Wed, 30 Jan 2013 19:30:57 GMT

Re: The hyperthyroid cat with normal bloods?

Kate Richardson — Tue, 29 Jan 2013 18:32:31 GMT

[quote user="Jillian Hall"]

To go off at another tangent....

How low does the T4 have to be before you think its veru unlikley to be the problem? With T4s around the 40 mark Im quite happy to run fT4 or repeat bloods in a month. I PTS a cat today that was polyphagic, losing wt, palpable thyroid, incr ALT etc etc with a T4 of 17 on bloods a few weeks ago. The owner had already decided not to take it any further so didn't get a chance to repeat bloods - but at 17 would you still be suspcious it was just on its way up?

[/quote]

1) lab error- I would always re run the test or ask the lab to re run it if the results doesn't fit to be sure of the result.

2) concurrent disease causing suppression, however usually fairly obvious concurrent disease eg severe dental disease, congestive heart failure

3) not hyperthyroid and other disease with similar clinical signs

How high was the ALT?

Re: The hyperthyroid cat with normal bloods?

Jillian Hall — Tue, 29 Jan 2013 18:18:03 GMT

To go off at another tangent....

Re: The hyperthyroid cat with normal bloods?

emerald — Mon, 28 Jan 2013 16:54:21 GMT

In response to the original post, I had a cat with a suspision of hyperT4 with clinical signs and a palpble goitre, she had high norm T4, T4 equilibrium dialysis was normal, the cat was confirmed hyperT4 by T3 supression test.

In respone to the second question, I would also be concerned about a more sinister cause of the symptoms eg thyroid carcinoma?

Re: The hyperthyroid cat with normal bloods?

Rob Davis — Wed, 23 Jan 2013 15:57:56 GMT

[quote user="Kate Richardson"]2) Does this cat have a thyroid adenocarcinoma rather than an adenoma? Can you palpate the thyroid and is is getting larger? [/quote]

Several years ago I had a cat which needed 6 neo-mercazole tablets daily to get its t4 level normal (this was pre felimazole and vidalta). I did a thyoirdectomy and sent the very large gland for histopathology and it was indeed an adenocarcinoma (the only one I have ever diagnosed). Within a couple of months of surgery his t4 level was over 300nmol/l again!

Re: The hyperthyroid cat with normal bloods?

Anthony Dennison — Wed, 23 Jan 2013 10:46:45 GMT

Thanks for the advice Kate, I will forward it on to the cat's normal vet who will be speaking to the owner today. We will be doing full bloods in 2 weeks time to assess the effect of high dose Vidalta, so I guess we will pick up any other abnormalities then.

The owner has told a previous vet she can't do twice daily dosing as she is always out in the evenings doing things (a very well off lady that lives in a rather large mansion on the sea front in Lytham), so think over the next 2 weeks we will try looking closely at the compliance issues. We do know of a couple of our clients who have sent their cats for RIT, so we might try getting their experiences on paper!

Re: The hyperthyroid cat with normal bloods?

Kate Richardson — Wed, 23 Jan 2013 09:13:48 GMT

Hi Anthony

I think this is a big dose and yes you will get rare cats that need it, but I would consider the following first:

1) compliance- is the cat really and truly getting the full dose daily. Also make sure she isn't crushing the tablets. Something seems a bit wrong if that cat is only ravenous in the mornings, but that may just be this cat.

2) Does this cat have a thyroid adenocarcinoma rather than an adenoma? Can you palpate the thyroid and is is getting larger?

3) Carbimazole (vidalta)just doesn't work as well in some cats, so you really may need to consider changing to methimazole (felimazole)- it may save the owners a fortune! Radioactive iodine? although would guess from your post that owner won't want to be parted from her cat....Y/d is another option if the owner really won't change, but despite being quite excited about it initially, haven't been as impressed with it as would have liked, mainly from a compliance issue ie cats won't eat it, plus there are some other concerns that have been raised about it. However, if surgery or radioactive iodine are not options, then it is worth a try.

4) Really important- Is there any possibility this cat has another disease process going on to cause the same clinical signs eg IBD, diabetes, EPI, liver disease. Although a T4 of 44 is perhaps slightly higher than we would ideally like, it is not that high. Unless there is concurrent disease going on to suppress the T4. Plus very simple thing to do is make sure the cat has been wormed!

5) regarding side effects, are you just looking for clinical side effects or also sub clinical ie haematology/biochem changes- you can get some serious haematology dyscrasias which you may not be aware of without monitoring bloods.

Re: The hyperthyroid cat with normal bloods?

Anthony Dennison — Wed, 23 Jan 2013 08:36:05 GMT

[quote user="Stephen Courtney"]that is a HUGE dose and side effects would be expected. given the absence, I think that again points to a compliance issue. though you can't come right pout and say it, i would suggest to the owners that medication is clearly not workign for this cat and it is time to explore other options.[/quote]

The cat has been on 30mg Vidalta daily for almost 4 months now with no side effects, so I think increasing it by another 5mg and monitoring closely for side effects is all we can do at the moment. The owner is so anti-surgery: the cat had its right foreleg amputated a few years back, and although it was hospitalised she came in and spent the day with it in hospital!

Rajat - thanks for the tip on finding a good news story from another owner, I will do some digging!

Re: The hyperthyroid cat with normal bloods?

Stephen Courtney — Tue, 22 Jan 2013 23:02:51 GMT

Fair enough, I bow to your experience, but have almost never had anyone on > 20mg vidalta daily, or > 15mg felimazole daily, though i know the option to go higher is there.

Re: The hyperthyroid cat with normal bloods?

Andrew Kent — Tue, 22 Jan 2013 22:55:27 GMT

I really don't think that is an excessively high dose, I have used up to 45mg with no side effects in one case and I tend to be quite conservative with thyroid management. Andy

Re: The hyperthyroid cat with normal bloods?

Stephen Courtney — Tue, 22 Jan 2013 22:51:36 GMT

Having watched the webinar on antibiotic usage and the evidence of shocking fibbing on the part of owners, personally I would be very suspicious that this cat is not getting nearly as much medication as you think.

that is a HUGE dose and side effects would be expected. given the absence, I think that again points to a compliance issue. though you can't come right pout and say it, i would suggest to the owners that medication is clearly not workign for this cat and it is time to explore other options.

I have a cat which was on a similar dose rate that has been on YD for 2 months now ( a 21 year old cat weight <2kg on 25mg vidalta sid when I stopped the vidalta and started YD) - she is to tell the truth slightly heavier now, but clinically no more hyperthryroid than she was on meds, and has stopped the constant vomiting and itching the vidalta was causing so the owner is delighted, and at 21 years old I'm not unhappy either. /i think stopping vomiting has resulted in the weight gain rather than anything else but it is still relatively early days.

My single other YD patient is actually doing quite well right now!

Re: The hyperthyroid cat with normal bloods?

David Mills — Tue, 22 Jan 2013 22:37:10 GMT

Has it got unilateral goitre? If so unilateral thyroidectomy surgery is a great option - they last about 18m according to figures in my previous place (n = 76), and usually die of something else before the other side becomes a problem. For unilateral sx this can be done as a day case as there shouldn't be any worries about hypocalc post-op. 30 minute op, worries over. In most places it only costs about 3m worth of medication too. Obv only do if no azotaemia present.

Re: The hyperthyroid cat with normal bloods?

Anthony Dennison — Tue, 22 Jan 2013 22:33:06 GMT

Meds are given in chicken every morning. Its the reason once daily dosing is the only thing available, the owner can only give the tablets 1st thing when the cat is hungriest

Re: The hyperthyroid cat with normal bloods?

Rajat — Tue, 22 Jan 2013 21:56:32 GMT

[quote user="Anthony Dennison"]

Sorry to change the topic of this thread slightly, but I have a hyperthyroid cat that has been on 30mg Vidalta SID since September 2012, when it was increased from 20mg SID. In September the T4 was 76nmol/L (decreased from the last sample which was >90nmol/L). After a month of 30mg treatment the cat had put on weight but was still polyphagic and HR was 160bpm (probably pushing the limits for a stressy old cat in a consult?)

Bloods were taken yesterday which showed T4 to be 44nmol/L (IDEXX ref range 10-30 normal, 30-60nmol/L is grey zone for symptomatic cats). Urea and ALT had increased slightly also from previous. The cat has lost 350g, HR was 200bpm and is constantly crying for food, following the owner around the house.

I tried to point the owner towards other options, such as surgery and radioactive iodine. I don't think surgery is an option with the cat in it's current condition, but the owner is very anti-surgery, also very against having the cat hospitalised for radioactive iodine as she doesn't think he would cope away from home as he never has been.

MSD tech support have said to increase to 35mg SID for 2 weeks, look out for side effects and then bloods for haematology and T4 at the end of the trial period.

Anyone have any other ideas that could be tried? Twice daily dosing with felimazole is most probably a no-no as the owner finds it difficult to pill the cat and can only do it 1st thing in the morning when he is ravenous (the cat, not the owner).

[/quote]

Tricky case, I usually see side effects at these doses, max I used so far was 25mg SID. Some cats will not stabilise on tablets. I wonder if adding in y/d will have an impact as a last ditch effort. Sounds like you have a small way to go though with TT4 at 44. I think Andy's idea of giving with food is excellent.

I would continue trying to push owners towards surgery or RIT - maybe you could get them in touch with other geriatric cat owners who have had either procedure ? Sometimes a gentle word of encouragement from Joe Public works better than our professional advice

Re: The hyperthyroid cat with normal bloods?

Andrew Kent — Tue, 22 Jan 2013 20:57:42 GMT

Are the owners giving the tablets with or without food? Food increases absorption of carbimazole by (I think) about 40% so if currently not with food could start doing that which is equivalent to a dose increase. Andy

Re: The hyperthyroid cat with normal bloods?

Anthony Dennison — Tue, 22 Jan 2013 15:55:56 GMT

MSD tech support have said to increase to 35mg SID for 2 weeks, look out for side effects and then bloods for haematology and T4 at the end of the trial period.