Thyroid peroxidase is an enzyme which is produced in the thyroid gland and is important for converting T4 to the biologically active T3. If I produce antibodies to thyroid peroxidase I understand this indicates that the body's immune system is attacking the thyroid gland and impairing its function.
So, in layman’s terms does this mean, if I have higher levels of antibodies that I convert less of my T4 to T3 (or is that either too simplistic, or even wrong)?
I had many symptoms that resolved since taking T3 as well as T4, but I am wondering when/if I may need a higher dose of T3.
My peroxidase antibodies dropped initially when taking T4 and T3 (2022) but appear to be climbing again (still taking T4 and T3 in same amounts).
Any insights much appreciated.
Written by
Mothebear
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Thyroid Peroxidase antibodies don't mean anything to do with conversion. They signify that you have autoimmune thyroid disease/Hashimoto's disease.
Antibodies will fluctuate naturally throught the course of your life regardless of what you do although some say that eliminating gluten from their diet has reduced antibodies. Taking T4 and or T3 will not affect antibodies.
Higher levels of antibodies mean your thyroid has been attacked by your immune system more recently.
To assess your bodies ability to convert T4 to T3 you would have a genetic test looking at the DIO2 gene.
To assess if you need a higher dose of hormone you would do a blood test.
Recommended blood test protocol: Test at 9am (or as close as possible), fasting, last levo dose 24hrs before the blood draw, last T3 dose 8-12 hours before blood draw & no biotin containing supplements for 3-7 days (Biotin can interfere with thyroid blood results as it is used in the testing process)? Testing like this gives consistency in your results and will show stable blood levels of hormone and highest TSH which varies throughout the day. Taking Levo/T3 just prior to blood draw can show a falsly elevated result and your GP/Endo might change your dose incorrectly as a result.
Thank you Jaydee. I have done the Dio2 test and that underpinned my getting T3 prescribed. I also do my blood tests strictly as advocated on this site. My blood levels as recently tested by NHS and Medichecks are looking fine.
My question thus referred to the antibodies as possibly being a marker of a shift in the status of my thyroid and I take from your answer that they are not, so thanks again,
I have tested positive on Dio2 and so have been prescribed T3. I conclude I just need to monitor my bloods regularly as any shift in T4/T3 needs will show there.
Regenerus - £80 or so. Saliva test, results take a couple to three weeks. Fed back by their doctor £60 more, letter sent to GP - just your time. GP in my case had no idea all gene tests must be fed back by a medically trained individual and she had no idea what it was about. I just said print out the results for me and I will explain. Once I started explaining, her eyes glazed over and she said ‘you obviously know more about this than me’ I took the sheet and left, but it was the basis for my getting T3 prescribed by very angry endocrinologist! ‘This will cause a landslide’ she said, ‘I haven’t prescribed this for 7 years!
I don't have a thyroid due to papillary cancer. Surgery was 10 years ago. No radiation.
Thoughts on still running TPO and TSI labs? The levels have never been raised since surgery. Just wondering if there is ever a chance that these antibodies can ever show up/increase down the road in my type of scenario.
I don't want to keep spending money on these tests if I don't need to. (I do still test Tg and Tg antibodies yearly which I know is important to keep monitoring for cancer recurrence.) Thank you!
Just to clarify your first sentence, you don't know of a valid reason to continue running the TPO and TSI labs, correct? (Just wondering for knowledge sake, if it's ever possible for these antibodies to increase after a thyroidectomy.)
Also, I think it's interesting that Quest Diagnostics Lab here in the US gives the normal TSI lab value as <89. It seems like such a large window. Are all labs like that for TSI?
Correct. Even if you have antibodies, it's not clear they would be affecting anything.
Antibody ranges are odd. They can vary hugely.
Having a "normal" level of 100, then they might dilute and test again. If positive again, that would mean >200. But they wouldn't then go to 400, 800, etc. It really doesn't add any useful information.
(The units for some antibody tests are entirely arbitrary - sometimes they even put "AU/ml" meaning literally arbitrary units.)
I find it interesting that everyone challenges my assertion of the link between T3 and T4, and I only quoted from the explanation Medicheck gives with the feedback on T3! 🤷♀️
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