Query about reverse t3

[cjrsquared]

I think this is a question for Diogenes. Following some study for a course I have been thinking about t3. I have always assumed that a free t3 blood result will have a proportion of reverse t3 in the result. Is this correct?

And liothyronine medication, is it formulated with only the active t3 or is there a proportion of reverse t3 in the manufacture in the same way that salbutamol for example has equal proportions of the s+ and r- enantiomer? I haven’t been able to find any papers on the latter question.

The things that your brain thinks about in the small wee hours.

[fibrolinda]

You need to do the @ Diogenes for him to be notified.,, like this 😊 diogenes

[diogenes Remembering]

No to both questions. There is no reverse T3 in T3 medications of any quality. FT3 tests specifically test against FT3 only and the cross reaction with rT3 is fractions of 1% as stated in all pack leaflets as a formal requirement. There is no significant interference.

[cjrsquared in reply to diogenes]

Thank you

[diogenes Remembering in reply to cjrsquared]

Just to say there should be little or no rT3 in NDT, because the thyroid doesn't make rT3. Its only made by body cells as a T4 drain.

[Angel_of_the_North]

As far as I know, free t3 and rT3 are completely different and not included in each others tests. Total T3 includes both protein-bound (unusable) and unbound T3 (usable), but does not include rT3.