Thyroidectomy on cat with questionable kidney perameters

RE: Thyroidectomy on cat with questionable kidney perameters

Kate Richardson — Mon, 22 May 2017 18:29:42 GMT

So I wouldn't be thinking of a thyroidectomy in this case unless the hyperthyroidism is causing such severe clinical symptoms that the cat's welfare is at stake. Have you checked urine fully for infection that could be causing an increase in urea/creat. Like your other case, I think you need to go for a slower reduction in T4 to allow the kidneys to adapt. I would go for 1.25mg methimazole sid for 3-4 weeks, then increase to 2.5mg sid if nec and see how the cat does clinically as the thyroid level drops slowly.

If the cat is difficult to medicate then sid dosing is fine (2.5mg bid=5mg sid) and the trans dermal gel might be a good option. But you need to see where those kidneys sit before committing to surgery. If the cat stabilises well on slow redction in T4, then you could consider surgery then

NB re unilateral v bilateral- I would only remove the affected gland so most cases are unilateral initially, but the other gland usually beomes affected in approx 18months time.

Hope that helps

RE: Thyroidectomy on cat with questionable kidney perameters

Jenny Harris — Mon, 22 May 2017 18:17:08 GMT

I guess it is tricky.... I think because there are concerns over post treatment hypothyroidism and azotaemia on survival times, then in this case you may want to carefully consider before something irreversible like a thyroidectomy. And maybe it is safer to stick with medication for the time being?

RE: Thyroidectomy on cat with questionable kidney perameters

Lucy Fleming — Mon, 22 May 2017 18:00:37 GMT

[quote user="Thomas Johnson"]I'm not convinced that managing cats like this is the best idea, just because the renal values improve with a slightly higher T4 doesn't necessarily mean that their long-term prognosis is any better, you may just be partially masking the renal disease.[/quote]

I tend to feel the same - I would just aim not to let the T4 drop below the lower end of the reference range.

RE: Thyroidectomy on cat with questionable kidney perameters

Lucy Fleming — Mon, 22 May 2017 17:59:01 GMT

That's interesting Jenny, thanks for that! I knew that with the tablet meds you were just meant to be consistent about with or without food, so logical I guess that it would be the same...

RE: Thyroidectomy on cat with questionable kidney perameters

Thomas Johnson — Mon, 22 May 2017 17:58:04 GMT

[quote user="Jenny Boyd"]

for this cat I would consider aiming for T4 in the upper half of the ref range, by lowering the dose of the thyronorm a bit, and would not do a thyroidectomy at this time. I know you say the cat is stressy- can the thyronorm be put in the food if not already?

[/quote]

I'm not convinced that managing cats like this is the best idea, just because the renal values improve with a slightly higher T4 doesn't necessarily mean that their long-term prognosis is any better, you may just be partially masking the renal disease.

RE: Thyroidectomy on cat with questionable kidney perameters

Jenny Harris — Mon, 22 May 2017 17:54:33 GMT

Hi Lucy-

not true ! Bioavailability may actually even be better. They just haven't (and won't) do the studies to prove it as it's tricky to do so.

as long as it's given the same way every day that's fine, and you just need to find the correct dose via a little trial and error at the start.....

RE: Thyroidectomy on cat with questionable kidney perameters

Lucy Fleming — Mon, 22 May 2017 17:43:36 GMT

I think the bioavailability of thyronorm is quite poor if put in the food - it specifically says on the instructions not to do so.

What about transdermal methimazole gel?

RE: Thyroidectomy on cat with questionable kidney perameters

Jenny Harris — Mon, 22 May 2017 17:39:54 GMT

RE: Thyroidectomy on cat with questionable kidney perameters

Bob Russell — Mon, 22 May 2017 17:39:25 GMT

I would prefer these to remain on medication rather than surgery or radioactive iodine treatment. Medication dose may be reduced slightly to see if a better balance can be achieved between thyroid levels and renal function.

I have some that have coped with medication for hyperthyroidism plus dodgy kidney function. Explain to owners the benefits and the price of thyroid level control. Most seem happy to continue with medication!

RE: Thyroidectomy on cat with questionable kidney perameters

Lucy Fleming — Mon, 22 May 2017 17:36:25 GMT

Hopefully someone who does more thyroidectomies might be along to advise in a bit, I tend to end up managing all mine medically for various reasons, along with the odd radio-iodine referral.

RE: Thyroidectomy on cat with questionable kidney perameters

dachsie_4 — Mon, 22 May 2017 17:33:30 GMT

It is a 'stressy' cat so surgery would be better long term, but just very of the after effect. And the cat is looking so much healthier on the thyronorm I think that it has been hyperthyroid for a while now. Pick trouble up on pre-anaesthetic screening.

RE: Thyroidectomy on cat with questionable kidney perameters

Lucy Fleming — Mon, 22 May 2017 17:24:55 GMT

My understanding of these cases (any endocrinologists will correct me if incorrect I'm sure!) is that this cat in fact always had renal disease, it was simply being masked by the increased GFR caused by the thyroid disease. However, I have heard before that you very much want to avoid these cats dipping in to the 'hypothyroid' range - which potentially might be a risk with a bilateral thyroidectomy.

I think a full and frank discussion of the potential risk: benefit ratio of surgery with the owner would be for the best. Is it difficult to medicate, or is it a young-ish cat that might have many years medication free after surgery? If not, I might be inclined not to rock the boat if everything going well.