Short-term biological variation of serum thyroid hormones concentrations in clinically healthy cats.

[helvella]

As with humans, so with cats. At least as regards reference ranges for populations versus individual cats.

Domest Anim Endocrinol. 2019 Sep 5;71:106389. doi: 10.1016/j.domaniend.2019.106389. [Epub ahead of print]

Short-term biological variation of serum thyroid hormones concentrations in clinically healthy cats.

Prieto JM1, Carney PC1, Miller ML1, Rishniw M1, Randolph JF1, Lamb SV2, Place NJ2, Peterson ME3.

Author information

1 Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA.

2 Department of Population Medicine & Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA.

3 Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA; Animal Endocrine Clinic, New York, NY, USA.

Abstract

Thyroid disease is common in cats, but little is known about the biologic variability of serum thyroid hormone concentrations and its impact on diagnostic utility in either healthy cats or cats with thyroid disease. The purpose of this study was to determine the biological variation, index of individuality, and reference change values for thyroid hormones and thyroid-stimulating hormone (TSH) in clinically healthy cats. Serum samples for analysis of total thyroxine (T4), triiodothyronine (T3), free T4 by dialysis, and TSH were obtained weekly for 6 wk from 10 healthy cats, then frozen until single-batch analyzed. Data were evaluated for outliers, and we determined the CV within individual cats (CVI) and between individual cats (CVG) for each hormone and the variation between duplicates or analytical variation (CVA). The index of individuality and reference change values for each hormone were then calculated. Serum concentrations of total T4, free T4, T3, and TSH all showed greater variation between cats (CVG) than within cats (CVI). Total and free T4 had an intermediate index of individuality (1.1 and 1.2, respectively), suggesting that these hormones would be best evaluated by a combination of their population-based reference intervals and reference change values. Serum TSH concentrations had high index of individuality (1.8), suggesting this hormone would be best evaluated with reference change values rather than the population-based reference interval. Total T3 also had a high calculated index of individuality (1.8); however, T3 had high ratio of analytical variation (CVA) to within cat variation (CVI), so RCV could not be accurately calculated. This study demonstrates that clinically normal cats show considerable interindividual biological variation in serum thyroid hormone and TSH concentrations, whereas the intraindividual variability in hormone concentrations is much narrower. This suggests that for all serum thyroid hormones, but especially serum TSH and T3 concentrations, comparing individual cat's hormone results to a population-based reference interval may be misleading, especially in those with early or subclinical thyroid disease. Clinicians might improve the diagnosis of feline thyroid disease by establishing baseline concentrations of T4, free T4, T3, and TSH for individual cats (ideally when healthy) and applying reference change values to subsequent measurements.

Copyright © 2019 Elsevier Inc. All rights reserved.

KEYWORDS:

Index of individuality; Population-based reference intervals; Reference change value; Subject-based reference intervals; Thyroid-stimulating hormone

PMID: 31731251

DOI: 10.1016/j.domaniend.2019.106389

ncbi.nlm.nih.gov/pubmed/317...

Let us see the same conclusion applied universally, please, humans and cats:

Clinicians might improve the diagnosis of thyroid disease by establishing baseline concentrations of T4, free T4, T3, and TSH for individuals (ideally when healthy) and applying reference change values to subsequent measurements.

[HashiFedUp]

What does it all mean?! Over my head.

[helvella Administrator in reply to HashiFedUp]

The official range for TSH might be 0.4 to 4.0. That should be based on the whole population of adults without thyroid disoders. But my range, where I am fit and well, could be much narrower, say, 1.0 to 1.4.

To put it into an example with numbers (though made up as an explanation):

If a doctor checked my TSH and saw it was 1.8, they would say it is in range and there is no problem. That might be true for some people, but as my personal TSH range only goes up to 1.4, 1.8 is over my personal range.

[vocalEK in reply to helvella]

To further complicate matters, none of our lab's reference ranges were established on unquestionably healthy people. Typically, only when a doctor suspects possible thyroid problems does he or she send them for testing. So it is much more likely that the truly healthy top of the TSH scale is closer to 2 than to 4 or 4.5.

[Hidden]

That is discrimination. We demand equal rights for humans!!!

Of course, the average cat does think itself superior to us 😂😂😂

[helvella Administrator in reply to Hidden]

I don't get that concept - an average cat???

[Hidden in reply to helvella]

Oops. Should have said ALL cats

[RedApple Administrator in reply to Hidden]

It's often been said in this forum that vets are so much better at sorting out thyroid issues in animals than doctors are with humans.

[Hidden in reply to RedApple]

When my son phones this afternoon for his usual weekly chat,it is going to be fun.

He has two hypothyroid cats!🙀🙀

How do I compare I wonder ? 🤔

[bantam12 in reply to Hidden]

Are you sure the cats aren't hyperthyroid as that's very common in cats but hypothyroidism in cats is very rare so to have two would be extremely unusual.

[Hidden in reply to bantam12]

I may well be wrong ....I will reply after I have spoken to my son 😊

[Hidden in reply to bantam12]

My last cat became hyperthyroid. The vet didn't help much, I was the one who eventually guessed what the problem must be. He went very scrawny (worming didn't help) and had a ravenous appetite. The vet said he had a "Slight heart murmur". By the next visit his heart rate was so fast it was impossible to measure. Only then did the vet follow my suggestion and check the thyroid. But by then it was too late, and I still had to pay for the tests, medications and having him put to sleep when the meds didn't work

[bantam12 in reply to Hidden]

Sorry to hear that happened, we had 2 hyper cats, no problem with getting the diagnosis but both had partial surgery which didn't work so both needed the very expensive Thyronorm meds, luckily my daughter is a vet !

[Hidden in reply to bantam12]

Yes, it was sad, but happened 20 years or so ago, so one moves on...

[Hidden in reply to bantam12]

Would cat thyroid meds work on humans?

[bantam12 in reply to Hidden]

No idea and I wouldn't like to try !

[helvella Administrator in reply to Hidden]

They have the same active ingredients so, fundamentally, yes.

However, it is all too easy to miss an important factor such as an excipient which is OK for humans but not cats - or vice versa. Or, as a USA vet did, take her dog tablets and mistake the dose (took ten times as much as she should have done). Or maybe carbimazole isn't OK for cats but methimazole is?

[Hidden in reply to helvella]

"as a USA vet did, take her dog tablets and mistake the dose"

Oh dear, she must have been very ill after that!

[helvella Administrator in reply to Hidden]

She was!

Accidental Thyrotoxicosis Caused by Inadvertent Ingestion of Levothyroxine “Dog-Tabs” by a Veterinarian with Hypothyroidism

amjmed.com/article/S0002-93...

[Hidden in reply to helvella]

Even within a species what suits one may not suit another. I read for example that a normal human dose of paracetamol could kill a lion, yet someone told me they gave paracetamol to her cat and it was OK

[helvella Administrator in reply to Hidden]

She, and the cat, were very lucky:

Paracetamol: Cats are extremely sensitive to paracetamol toxicity. The feline toxic dose is 50 to 100 mg/kg. One regular strength tablet may be toxic to a cat, and a second ingested 24 hours later may be lethal. The signs of toxicity are brown gums, difficulty breathing, blood in the urine, jaundice and swelling.

agriculture.vic.gov.au/pets...

[TSH110 in reply to Hidden]

OMG!

[TSH110 in reply to helvella]

I wonder why dogs need c10x what we do and why some people can get away with taking a week’s T4 at one go so they don’t forget it. The link does not get me to the article perhaps she took a weeks worth of her dog’s meds or it was combination therapy?

[Hidden in reply to TSH110]

Here's the link to the original report. It does seem that dogs need a much higher dose than humans: amjmed.com/article/S0002-93...

[Hidden in reply to TSH110]

Oh, just realised it's the same link. Works for me. Strange

[TSH110 in reply to Hidden]

Eventually got to it it dumped me in a mobile version that refused to download but I decided to try the full site instead when I was offered a button to it - and there it was. I am on an iPhone 🙄

[Hidden in reply to TSH110]

Good. I was wondering whether to paste it on here. I use the desktop as much as possible - easier to see than a phone (Need new speck, lol)

[TSH110 in reply to Hidden]

Usually on the hoof iPhone is a museum piece but it struggles on and the cost of a new one makes me wince plus I wouldn’t be able to work it most likely....tho I’m sure I’d Eventually get the hang of one after all I mastered txting!

[Hidden in reply to TSH110]

Know the feeling. I have an android and couldn't even get it to start up at first. Kept pressing the button on the right, per instructions and nothing happened. Eventually found out I was holding it upside down!!!!

[TSH110 in reply to Hidden]

😂🤣😂 that’s so funny!

[LAHs in reply to Hidden]

I think so, my little hyper is on methimazole - a med used for humans. Of course you would have to step up the dose (human ~ 10 stone, cat ~ 10 lbs).

[TSH110 in reply to bantam12]

Is she better on thyroid issues than your doctor?

[bantam12 in reply to TSH110]

I'm afraid I can't answer that as I don't know, she is a large animal farm vet so doesn't treat dogs and cats, I have no problems with my GP.

[TSH110 in reply to bantam12]

Great you have a good doc 😉

[Hidden in reply to bantam12]

Yes,my mistake !! My son's cats were hyperthyroid which was diagnosed when they started losing weight...........not my problem!! .....most definitely Hypo.☹️

[RedApple Administrator]

Clinicians might improve the diagnosis of thyroid disease by establishing baseline concentrations of T4, free T4, T3, and TSH for individuals (ideally when healthy)

Knowing what we know now, this seems so very obvious doesn't it. Lumping everyone into a standardised range and classing that as being healthy regardless of any other evidence to the contrary is both non-sensical and cruel!

So, we should test everyone's TSH, FT4 and maybe antibodies too, early on in adult life (e.g. age 18 or 21 perhaps) as a matter of course, and keep that info permanently on record. This gives a baseline to compare with if/when thyroid tests are done at any later date. This baseline record would then be taken into account when assessing subsequent thyroid test results, alongside symptoms, to make a more accurate diagnosis of whether thyroid disease is or is not an issue.

Recognising that we are all unique individuals is fully accepted and encouraged in so many other aspects of life, and yet when it comes to thyroid disease, we're all supposed to fit into a standardised category.

[diogenes Remembering]

This sentence in the Abstract took my eye:

Clinicians might improve the diagnosis of feline thyroid disease by establishing baseline concentrations of T4, free T4, T3, and TSH for individual cats (ideally when healthy) and applying reference change values to subsequent measurements.

The obvious question arises: Why not humans too? We have exactly the same variation in the population.

[wellness1]

Thanks for posting this. I can't read about feline thyroid disease without feeling upset about the role of endocrine disrupting chemicals in their, and our, thyroid health. (fyi, below links discuss cats, chemicals and thyroid disease)

acs.org/content/acs/en/pres...

healthunlocked.com/thyroidu...

[DippyDame in reply to wellness1]

....and the possible role of EDCs in (human) Thyroid Hormone Resistance. Much research still required here...

The endo I saw briefly refused to believe I could have RTH despite the fact that my (current) dose of 137.5mcg T3 causes no symptoms of overmedication and has greatly improved my health. When questioned he could not offer an explanation other than offering a suggestion that it was like getting in a car.....mostly you arrived safely but sometimes you might crash!! I kid you not!

His comment, "Since it seems to be working perhaps you should maintain the status quo", and then added the caveat, "but that wouldn't be my advice".

I left ...never to return!

The cause may not be genetic as he claimed (no test) but he dismissed the possibility of any other cause.

No wonder over a 100,000 people have arrived at TUK looking for help after medics have failed them.

So yes....I'm not surprised we consider a visit to the vet as a preferable option. They have opened their minds...and here I refer to diogenes comment above, "Why not humans too?"

TUK has succeeded where the medical profession has failed!

Thank you.

[wellness1 in reply to DippyDame]

Yes absolutely, much research required on health impacts of chemicals and much research still required on several aspects of thyroid disease.

As for the suggestion, "...that it was like getting in a car.....mostly you arrived safely but sometimes you might crash!!", would he recommend people not drive cars? It's a shame you've not been more supported, but wonderful that you've found something that works for you, with the help of this forum, such a wonderful resource.

[TSH110]

Cute cat

[LAHs]

Oh, that's one beautiful pussy cat!