T3 or Ft3?

[nara8]

Hello everyone.I'm reading the ATA guideline for managing hypothyroidism. I've noticed they mentioned tsh, t3, and ft4 to be checked. My endo only orders TSH so I want to ask another doctor to test thyroid hormones. Should I test T3 or Ft3? And I watched one of Dr. Bianco's videos on youtube and he said he always checks t3 not ft3. Now I'm confused.

[helvella Administrator]

The problem with Total T3 is that it is influenced by the amount of binding proteins in your blood. And those are affected by many things.

The problem with Free T3 is that the actual tests are challenging to design such that they are consistent and accurate.

And it is often claimed that Free T3 is too variable. But many research studies actually show it is more stable than TSH and nothing like as variable as claimed.

But I'd go with Free T3.

[nara8 in reply to helvella]

Thank you helvella. Is it right that those accurate methods of measuring Ft3 are only used in research settings and not in routine tests for patients?

[helvella Administrator in reply to nara8]

No. At least, I don't think so.

The accuracy isn't the absolute issue with research vs patient tests. It is more due to being less sensitive to interference by anything that affects the immunologic tests.

And all tests require a degree of scepticism. None is perfect in all circumstances.

[nara8 in reply to helvella]

Thank you. I hope my mistakes in English haven't bothered you.

[helvella Administrator in reply to nara8]

I didn't notice any!

[DippyDame]

I would go by FT3 then you can compare like with like.... FT4 with FT3....to establish T4 to T3 conversion status

High FT4 with low FT3 = poor conversion

[nara8 in reply to DippyDame]

Thank you very much DippyDame.