Palpable goitres and TT4 in cats

RE: Palpable goitres and TT4 in cats

Noweia — Fri, 10 Jan 2020 19:22:48 GMT

I have done one - one sided goitre, huge mass, signs consistent but bloods always returned negative. Ended up removing it anyway and signs subsided.

RE: Palpable goitres and TT4 in cats

Lucy Fleming — Fri, 10 Jan 2020 19:19:11 GMT

I can see the temptation, but I personally probably wouldn't. I've actually never done a thyroidectomy after 12 years in practice. Admittedly I'm not really a big "surgeon" so perhaps I don't sell it that much, but I don't often find owners are that keen. A blood test to confirm needn't be expensive (you could theoretically just run a TT4 to confirm, though as others have pointed out checking for concurrent disease is also useful), so if they can't even afford that a thyroidectomy might financially be out of reach?

Having said that:

Pros: as you mentioned, potentially "curative"

No need for ongoing meds (?) or monitoring

Lower overall cost (probably the lowest)

Low risk of complications

Cons:

Without bloods, small risk of misdiagnosis (pretty small, admittedly)

Surgery on geriatric patient - risk of concurrent disease, and increased cardiovascular stress of hyperthyroidism. Medical management initially would reduce surgical risk?

Potential long/ short term complications eg calcium balance (law of sod dictates that the patient this occurs in would be the cost-restricted one you were trying to do your best by)

Majority of cases will go on to develop disease in contralateral gland - but bilateral higher risk of complications. Ectopic tissue (mainly at the heart base) also fairly common

I tend to find medical management is usually what owners go for while they are deciding, and usually stick with it as it turns out to be easier than they expected. Probably a higher cost overall, especially if the cat lives a long time, but perhaps the smaller "lump sums" are more manageable?

Personally, if it was my cat I would send for radioiodine

RE: Palpable goitres and TT4 in cats

Beats — Fri, 10 Jan 2020 16:04:41 GMT

I check the urine during the consult, so that eliminates diabetes and kidney problems in many patients. Not suitable in every case in my mind Julian, but I certainly do thyroidectomies without running blood tests of any sort on occasions (but would only ever do unilateral in this circumstance personally)

Maldigestion/malabsorption and IBD/small cell lymphoma do not typically present with an obvious goitre.

RE: Palpable goitres and TT4 in cats

Sarah Keir — Fri, 10 Jan 2020 15:00:02 GMT

Or maldigestion/malabsorption so IBD/small cell lymphoma.

RE: Palpable goitres and TT4 in cats

Rob Loxley — Fri, 10 Jan 2020 14:34:40 GMT

[quote userid="3094" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/28767/palpable-goitres-and-tt4-in-cats/218701"]Reduced costs, faster cure simply by not waiting for laboratory test results to come through as well. And effective.[/quote]

Just a few that immediately spring to mind: anaesthetising a (probably) geriatric cat without checking for any concurrent diseases - add liver disease or diabetes to your kidney disease; doing surgery to remove a goitre without checking it is actually biologically active and the cause of the cat's problem (as in this thread I'm sure we've all blood tested cats with goitres and found T4 normal).
The cost to the practice of doing bloods is not that great, and many practices can do them all in-house.
I'm sure it can be effective in some cases where there is a favourable following wind behind you, but I suspect you'll get bitten fairly quickly. And I'm not sure who is going to support you that doing thyroidectomy without any investigation 1st is a sensible standard approach, should it come to a complaint...

RE: Palpable goitres and TT4 in cats

Julian Earl — Fri, 10 Jan 2020 10:12:03 GMT

Is there any justification for thyroidectomy in cats with palpable goitre and classic signs without the need for blood tests as well? Meaning, approaching these cases the way we [ we = meaning me!] used to do? The immediate disadvantage is having no measure of kidney function available in advance but all of the cats that I can remember seeing when hyperthyroidisms was first identified or highlighted as a differential for these old cats losing weight despite a god appetite invariably responded well to thyroidectomy. I've been a fan of surgical treatment for this reason ever since though latterly with blood tests involved first. By and large, surgery is a one-off tretent with negligible follow-up therapy required IME.

Why take this route? Reduced costs, faster cure simply by not waiting for laboratory test results to come through as well. And effective.

Any thoughts? Or are you just going to shoot me down in flams for suggesting this approach?

Thanks in advance.

RE: Palpable goitres and TT4 in cats

Noweia — Thu, 09 Jan 2020 21:44:10 GMT

With rapid weight loss if ill I would expect T4 to be in teens. (Worked at a V4P where senior blood panel is offered yearly as a routine and most normal were in 20s, few in 30s)

RE: Palpable goitres and TT4 in cats

Sarah Keir — Tue, 07 Jan 2020 15:28:04 GMT

And even then often need to resort to clonality testing.

RE: Palpable goitres and TT4 in cats

Anthony Dennison — Tue, 07 Jan 2020 15:19:47 GMT

[quote userid="16672" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/28767/palpable-goitres-and-tt4-in-cats/218561"]

Abdominal ultrasound has some use here, no? Loss of layering = more likely lymphoma and generalised thickening = more likely IBD? Then +/- biopsies?

In reality, if it's not a horribly obvious lymphoma I stick them on a hypo diet and see if they respond

[/quote]

No, IBD and lymphoma can have similar appearances. The really advanced lymphoma cases where you can feel a mass on abdominal palpation maybe, but even then not always. Biopsies are required to tell the difference and even then there's disagreement unless the WSAVA intestinal biopsy framework is used

RE: Palpable goitres and TT4 in cats

Sarah Keir — Tue, 07 Jan 2020 14:44:18 GMT

If only it was that easy Martin. Can be difficult with biopsies even.

RE: Palpable goitres and TT4 in cats

Martin Hamilton — Sat, 04 Jan 2020 17:06:58 GMT

Abdominal ultrasound has some use here, no? Loss of layering = more likely lymphoma and generalised thickening = more likely IBD? Then +/- biopsies?

In reality, if it's not a horribly obvious lymphoma I stick them on a hypo diet and see if they respond

RE: Palpable goitres and TT4 in cats

Sarah Keir — Sat, 04 Jan 2020 11:23:40 GMT

No easy way

RE: Palpable goitres and TT4 in cats

Lucy Fleming — Fri, 03 Jan 2020 21:02:26 GMT

[quote userid="8958" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/28767/palpable-goitres-and-tt4-in-cats/218525"]Question is when do you re-sample for TT4?[/quote]

Hills claim can control T4 levels in 3 weeks, so a similar time period to other forms of medical management, I guess (I usually suggest 4-6 weeks, though I know most suggest you can sample sooner).

The only experience I really have with y/d was my parents trying it on our own cat (vet daughters are no use for pilling cats when they live at the other end of the UK). Initially was pretty positive, but unfortunately as it did what it was supposed to and she was no longer polyphagic, she then refused to eat it...

RE: Palpable goitres and TT4 in cats

Neil Wheadon — Fri, 03 Jan 2020 17:26:48 GMT

[quote userid="9515" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/28767/palpable-goitres-and-tt4-in-cats/218524"] IBD/small call lymphoma is very common and they don't always has diarrhoea - don't be caught out![/quote]

Easiest way to rule this out Sarah?

Neil

RE: Palpable goitres and TT4 in cats

Neil Wheadon — Fri, 03 Jan 2020 17:15:26 GMT

Good grief, follow up from a locum

I blood sampled and came in today at 50, so risen from 44. Palpable goitres, so i agree that 60 is just too high. Maybe IDEXX should ask for feedback, look at this

The client has chosen to start on Y/D, having been offered 6 options, only the second I've seen. Strikes me as being the safest way to treat a case where not over 60. Question is when do you re-sample for TT4?

Neil

RE: Palpable goitres and TT4 in cats

Sarah Keir — Fri, 03 Jan 2020 17:02:54 GMT

I would recommend you always confirm your suspicion of hyperthyroidism with a blood test and to bring up if any concurrent problems such as pre-exinsting azotaemia. Polyphagia and ravenous appetite - IBD/small call lymphoma is very common and they don't always has diarrhoea - don't be caught out!

I treat any TT4>30 as highly suspicious in an older cat, I think the reference range is far too high.

RE: Palpable goitres and TT4 in cats

Joyce Whitehead — Fri, 03 Jan 2020 16:02:49 GMT

Yes I’d agree with Anthony, if they look clinically suspicious and the Tt4 is high normal I’d start treatment. This idexx flow chart seems to agree. I’ve found a few stabilise in quite a low dose of meds, but a few months down the line start to lose weight again and at that point have much higher TT4 levels.

idexxcom-live-b02da1e51e754c9cb292133b-9c56c33.aldryn-media.com/.../total-t4-testing-guide-cat-unified.pdf

RE: Palpable goitres and TT4 in cats

Anthony Dennison — Fri, 03 Jan 2020 15:01:16 GMT

[quote userid="8958" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/28767/palpable-goitres-and-tt4-in-cats"]Seen by another vet a month ago this 12 year old cat had lost a kilo and had had bloods (TT4 42) yet I could feel 2 goitres,[/quote]

Grey zone between 30-60 and clinical signs consistent with hyperT4 - I would treat. Likely early stages of disease or there's some non-thyroidal illness causing suppression.

RE: Palpable goitres and TT4 in cats

Rob Loxley — Tue, 31 Dec 2019 08:39:32 GMT

IME the earlier you test, the more of these borderline cases you can find. We tend to get the lab to run freeT4ed in such cases

RE: Palpable goitres and TT4 in cats

Lucy Fleming — Tue, 31 Dec 2019 08:25:03 GMT

When I was speaking to one of the IDEXX vets a while ago, they mentioned there was a debate among clinical pathologists that the upper end of the reference range for TT4 should be dropped by about 10 nmol/L, as I presume quite a few cats have clinical signs accompanied by TT4 in the 50-60 sort of range.

So:

1) Potentially quite a few. I had one recently with tachycardia, gallop rhythm and weight loss (though interestingly no palpable goitre) and a T4 of 69.5 which is only just elevated (she was a fatty so I was almost more suspicious of diabetes to be honest!). It does seem an odd situation to have so many potential "false negatives".

2) Probably most of them. I've had ones before where the owner has declined free T4 but we've retested later and confirmed hyperthyroid with elevated TT4. Most have been a longer time period than 4-6 weeks though. I wonder whether the one you saw has developed the goitres since its last check. Did the other vet's notes say whether goitre was present/absent? I must admit I wouldn't always specifically record if no goitre. (You can also get non-functional thyroid nodules, but not common at all)

3) By routinely, do you mean in all suspect hyperthyroid cats you sample? I would probably say no. If clinically suspicious and high normal TT4 I would suggest it as a follow up, but I don't find I'm seeing enough in that category to justify it routinely.

RE: Palpable goitres and TT4 in cats

Beats — Tue, 31 Dec 2019 08:09:46 GMT

seen by a vet for another reason? sick for another reason leading to lower T4?

My general experience (Axiom Lab) is that all but the very smallest of small goitres have a TT4>50-60. I haven't felt the need to assay another form of thyroid hormone in a cat in the last 10 years.

If the clinical signs are consistent with hyperT4 and there is an obvious goitre, then I don't necessarily take a blood sample [not needed for diagnosis]. I'd often start on 2.5 or, more commonly, 5mg felimazole once daily and weigh again in a few weeks.

Rarely, I think I have confused deep cervical LNs with a goitre - so I would blood sample for T4 if I was in doubt re my palpation, or if there was no palpable goitre and wanted to be 100% sure that clinical signs were not due to hyperT4 [also extremely rare in my experience].

For your cat: I would put on felimazole 2.5mg once daily and reweigh in a few weeks [assuming hefty appetite, convincing goitre and no other explanations such as large abdominal mass].

RE: Palpable goitres and TT4 in cats

Martin Hamilton — Tue, 31 Dec 2019 01:24:16 GMT

The lab that we use (in Ontario, Canada) uses a reference range of 10 - 52nmol/L for TT4. However, above 35nmol/L they always have a pathologist comment recommending to check a freeT4 by EQD if clinical signs are present as the cat may still be hyperthyroid.

I'd probably check the free T4, but that's because this lab got me used to doing it. Most of the ones that seemed to have high-normal TT4s but were in the 40's and had clinical signs ended up being hyperthyroid in the end.