Thyroid Function

[Jiffer]

Atlas is an 11 year old male brindle greyhound. He has normally weighed between 85 and 90lbs until the past year; he was 88lbs in April 2009. He lost weight and dropped to about 80lbs despite giving him nearly a full cup of extra food a day once I started seeing the difference in him (so probably since November I've upped his food). He does not have any intestinal parasites, we haven't increased/decreased exercise, nor has there been any event to cause this reaction. He has always been a very laid back and lazy dog, but not so much so that we'd worry about him. He does have a grade 3/4 heart murmur which began when he was 8 years old. It has not changed since being diagnosed.

 

He went for his pre-dental senior panel and the results came back with his urea and creatinine slightly elevated (we're addressing this with an improved diet), and low thyroid. fT4 normal: 14 - 40; Atlas' 13.4

So it was decided to try a low dose (0.6mg) of Thyroxine to see if he would gain some weight back.

 

One month later, we take him back in for a recheck. He has gained back 2lbs ! The only change was the medication; we've started his food change today. They redid bloodwork and this time ran just the T4 test; I really wish he had redone the fT4 too. He came back at 5.3 where the normals are 15 - 51. So our vet wants me to double his dose of Thyroxine to 1.2mg (0.6 twice a day). I admit this number seems awfully low, even for a greyhound.

 

I guess I'm just looking for any thoughts on this. Most of the information I find indicates that if there are no symptoms to not bother treating; but can we discount weight loss as a symptom since normal hypothyroidism means weight gain? Given that he has gained weight since beginning the meds seems to imply that perhaps he's just backwards.

 

He's such a good boy, I just want to do right by him and I do trust my vet. He does a lot of research and has quite extensive greyhound knowledge (he's aware that most of their blood tests can be wonky; even referring to Uber's increased levels as "normal greyhound" on his paperwork).

Edited February 28, 2010 by Jiffer

[Guest Swifthounds]

If you suspect thyroid issues at all, I would thoroughly recommend a thyroid panel done by Dr. Dodds at Hemopet. Your vet can draw the blood and you can drop it in the mail. Instructions for everything are on the website. Hemopet - Thyroid Panel

[RedFawnMom]

I was just researching this yesterday, as Lucy's thyroid #'s came back low when we had blood work done earlier this week.

 

From OSU:

 

http://www.vet.ohio-state.edu/2098.htm

 

A controversial area in Greyhound medicine has been how to test for thyroid function. It has been stated numerous times in the lay literature that there is a high proportion of hypothyroid Greyhounds, and a large number of dogs have been placed on thyroid hormone supplementation for life on the basis of "low levels of T4". However, scientific evidence suggests that Greyhounds have resting (basal) T4 and free T4 concentrations below the reference range for the dog. Gaughan and Bruyette demonstrated that the mean basal T4 concentration in Greyhounds is 13.9 nmol/L (reference range, 2.1 to 25.7 nmol/L), the mean basal free-T4 concentration is 11.3 pmol/L (reference range, 0 to 23.5 pmol/L). In contrast, non-Greyhound dogs had mean basal T4 concentrations of 25.7 nmol/L (reference range, 10 to 45.5 nmol/L) and free-T4 concentrations of 19.3 pmol/L (reference range, 3.9 to 39.9 pmol/L). After TSH or TRH stimulation, Greyhounds' T4 concentrations were also significantly lower than in the control group. Hill et al also demonstrated that total T4 concentrations increase and TSH concentrations decrease after racing 500 m.

 

Here's another article: http://greythealth.com/hypothyroid.htm

 

That one explains "sick euthyroid" - if there is some other type if illness going on, the thyroid #'s can come back low. I would think weight LOSS would more likely be due to some other kind of illness, which could also be causing the thyroid counts to come back low.

Edited February 28, 2010 by RedFawnMom

[Batmom]

I prefer not to give meds until a full thyroid panel has been done. I recommend MSU's premium panel + interpretation as it includes fT4ed, TSH, and interpretation.

 

At this point, tho, there is no point in having a panel done by MSU or Hemopet -- dog has to be off meds for @ 6 weeks for a panel to be meaningful.

 

On the recheck, how long after giving meds was the blood drawn? That can make a difference.

 

Here is a whole bunch of info about thyroid function in dogs: http://www.animalhealth.msu.edu/Sections/Endocrinology/Thyroid_Canine.php

 

And here is some info about monitoring thyroid levels in a medicated dog: http://www.animalhealth.msu.edu/Sections/Endocrinology/Monitoring.php

 

Best luck to you and your pupper!

[Jiffer]

Thanks. The recheck was done about 10.5 hours after the dosage was given. Ideally they would have preferred 12 hours after but they wouldn't be open that late.

 

I've been reading a lot of info on this on the web, plus airing my concerns with my vet so please don't assume that I started him on meds without giving it full consideration. Medicating my dogs is not something I do lightly.

[Guest Swifthounds]

Quick question for the OP: I noticed you had pre-dental bloodwork done. Did you do the dental or hold off? Bacteria in an unclean mouth are dumped into the blood stream and can affect organ function.

[Jiffer]

Swifthounds: No, we have not done the dental yet. It was in his best interests to hold off until we figure out the thyroid issue. His teeth are in relatively good shape, he has a couple that have gum recession and need removal (Brushing is a big part of our bedtime rituals here so I've managed to keep their teeth in pretty good condition).

[Batmom]

No question about your having his best interests in mind! I posted the MSU links because there's a lot of good info there that might help figure out whether response to tests is what you should expect and whether to up the dose now, wait and recheck, etc.

[CaliforniaGreys]

Ideally they would have preferred 12 hours after but they wouldn't be open that late.

 

From what Hemopet and my own vet has said, 12 hours is too long. According to the above, it should be 4-5 hours after the dose

[Guest MnMDogs]

That's actually what my vet goes by as well when re-checking Mork.

 

ETA - I tried to quote Claudia - I meant that my re-tests at 4 - 5 hours after a dose.

Edited February 28, 2010 by MnMDogs

[greyhead]

Yes, it does happen that hypothyroid dogs (and people) show symptoms that are usually associated with hyper-t, such as normal to low weight or normal to thick hair.

 

Hope that information helps.

[Jiffer]

Thanks everyone.

 

I'm not sure about the retesting timeline since the vets office specifically asked that we retest as close to 12 hours as we could. But, his next retest is on March 26 in the late morning so it will be about 4 hours after his dose so maybe that will give us a better idea.

 

<Sigh> Why do they have to get older?

[Guest FullMetalFrank]

That is odd that they wanted to test him @ 12 hours after his dose, it's usually preferred to be 4 to 5 hours. I need to get Frankie in for a re-check, too. He is on .7 twice a day. He is another dog who did not show all of the typical symptoms; he was losing weight inexplicably but now he is good and solid on his weight. He also had darkening of the skin, some alopecia, and was a bit more lethargic than usual. All of those conditions have improved on the meds, along with the PD/PU that first brought us in to the vet's.

[Batmom]

Per MSU, as long as you're testing 3 hours or more after the last dose, it doesn't matter when. It's just that you're looking for a different target range if you test earlier vs. later (shortly before next pill, for example).

[Guest DorasMom]

Hi Jen, Dora has thyroid issues too and when she gets her blood work done they request it be about 5hrs after her pill. The number we strive for with her is 12-14. That's the area where she does the best.

[Jiffer]

Thanks again everyone. I'll certainly keep everyone posted on my sweet boy.

 

FullMetalFrank: I haven't found much information on dogs who experience different symptoms than the "usual" so it's good to know that there are others out there.

[Guest FatpatsMama]

Do not increase his thyroid doseage unless you have a full panel done. I went through this with Fatpat, and he went into renal failure after TWO YEARS on the wrong dose of thyroid (.8 mg when it should have been .2!!!). Even when he dropped 15 pounds his vet said he didn't know what was going on and insisted the meds should remain the same. I would never increase a thyroid dose without a full panel of bloodwork, and a second opinion from knowledgeable greyhound owners. If not for Cathie Lambert and Marilyn her friend, and a new vet, I don't know what would've become of Fatpat. By the time we got help, he had to receive intervenous fluids for many months, because the overdose of thyroid meds damaged his kidneys. He leveled out at a .3 dose, and lived through it. Just a word of caution.

Edited March 1, 2010 by FatpatsMama

[Burpdog]

How long did you wait to retest? I usually start with .5 twice a day and wait 6-8 weeks before retesting.

 

but can we discount weight loss as a symptom since normal hypothyroidism means weight gain

 

Weight loss is also a symptom. The thyroid is the engine for the body and if it's not working, many things cannot function properly.

 

 

[Jiffer]

How long did you wait to retest? I usually start with .5 twice a day and wait 6-8 weeks before retesting.

 

He was on .6 daily from January 27 to February 26 when we did the retest, so it was 31 days.

Edited March 2, 2010 by Jiffer