Troublesome hyperthyroid

Re: Troublesome hyperthyroid

emerald — Thu, 06 Mar 2014 09:28:02 GMT

There is the option for topical thyroid meds off licence....

Re: Troublesome hyperthyroid

Tom Ward — Wed, 05 Mar 2014 14:26:35 GMT

[quote user="Utlendigur"]

Just back from a CPD evening by Dechra on felimazole. Their recommendation for cats that become azotaemic (Iris stage 1-3) after starting treatment is to keep the T4 in the lower part of the normal range, and that there is no significant difference in survival between azotaemic and non-azotaemic cats. Also said not to undertreat the hyperthyroidism as this is likely to lead to further renal damage.( Reference given was JVIM 24 (2010) Williams et al 1086-1092 + work done by RVC)

[/quote]

Indeed, that was my thought, I saw an online presentation that Tim did about that paper, but the vet at the radioactive I centre is not keen to proceed - possibly due to the risk of iatrogenic hypothyroidism? Her USG today is 1.022 which tells us very little I suppose in a non controlled hyperthyroid! I guess the fact that the t4 has not reached its original levels despite being off meds for 4wks may suggest there is some t4 suppression...

Re: Troublesome hyperthyroid

Utlendigur — Tue, 04 Mar 2014 22:13:11 GMT

Re: Troublesome hyperthyroid

Charlotte Marshall — Tue, 04 Mar 2014 19:22:06 GMT

[quote user="Martin Atkinson"]If you've had problems with Vidalta use Felimazole, supposedly you get more side effects than with thiamazole bit IME its much less.[/quote]

Theoretically as carbimazole is broken down to methimazole in the body if you have a reaction to one you would expect it to the other. Saying that I have had the occasional cat tolerate one and not the other. also there is the option to use much lower doses with the felimazole which may help.

Re: Troublesome hyperthyroid

John Flynn — Tue, 04 Mar 2014 19:17:27 GMT

WIthin reason, if I see symptomatic hyperthyroidism (and I see quite a lot I reckon), I treat it.

If cat doesn't tolerate meds for any reason, then I do thyroidectomy, but radioactive iodine is cleverer I suspect.

I don't particularly see how an elevated urea level is a contraindication to this.

Equally I think it would be pretty difficult to conclusively diagnose routine chronic kidney disease in a cat with known hyperT4 that wasn't being controlled (I'm open to suggestions on how people do this practically).

Finally, as I don't typically consider treating kidney disease with thyroid-supplementation (not yet, anyway - do other folk?), I can't see why this would alter my recommended treatment for the hyperthyroidism particularly?

Re: Troublesome hyperthyroid

Martin Atkinson — Tue, 04 Mar 2014 19:12:24 GMT

[quote user="Tom Ward"]sorry, it was 61mmol/L (ref up to 65mmol/L), so well into top 1/2 normal (so not controlled for a cat on med[/quote] The normal range is now recognised as 15- 40 mmol/l, most labs work on this if yours sticks with the old one change them. Then to be stable the T4 needs to be the lower end of that range so well below 30. I have a few which dip well below the 15 and are still showing no signs of hypothyroidism. If you've had problems with Vidalta use Felimazole, supposedly you get more side effects than with thiamazole bit IME its much less.

Re: Troublesome hyperthyroid

Charlotte Marshall — Tue, 04 Mar 2014 18:58:39 GMT

How about just symptomatic treatment of tachycardia and raised blood pressure if the cat is one which is eating well? There are plenty of cats out there that are living with thyroid levels like this I suspect as plenty don't get presented until T4 levels are well over 100.

If it's kidneys prove to be ok you could consider surgery.

Re: Troublesome hyperthyroid

Tom Ward — Tue, 04 Mar 2014 17:10:31 GMT

[quote user="James Laidlaw"]

What do you consider "borderline normal" T4? Lower half of reference range, or just about reference range?

[/quote]

sorry, it was 61mmol/L (ref up to 65mmol/L), so well into top 1/2 normal (so not controlled for a cat on meds, but not 100% diagnostic on a cat off meds, though this cat was initially diagnosed with 74mmol/L!

Re: Troublesome hyperthyroid

James Laidlaw — Tue, 04 Mar 2014 14:30:30 GMT

What do you consider "borderline normal" T4? Lower half of reference range, or just about reference range?

Re: Troublesome hyperthyroid

Utlendigur — Tue, 04 Mar 2014 13:39:42 GMT

I wouldn't jump to conclusions about the kidneys yet - small increase in urea alone could be due to other causes eg GI, reduced appetite (nb what were renal parameters like on vidalta?). Was creatinine normal? Also USG (or full works) as you have planned is the next logical step. Another option could be wait a bit and recheck T4 (+/- free T4) + biochem in another couple of weeks. Also what hyperthyroid signs recurred? - especially given the T4 was borderline - do you mean weight loss, pupd, vomiting/diarrhoea, tachycardia etc - anything else going on that could cause same signs? Probably also worth checking blood pressure at some point