T3 and it's impact on conversion of T4 to T3...

[joey82]

Hi,

When on combination therapy does the amount of T3 you take impact the conversion of T4 to T3?

For example, if you was on 75mcg T4 and 20T3 would the conversion of the T4 be worse if you increased the T3 to 30mcg of more?

I know lots of factors can impact conversion but I just wanted to know in isolation whether T3 has an impact on conversion.

Many thanks in advance.

[greygoose]

I'm not sure anybody really knows. I don't think much research has ever been done on that sort of thing. And once you're taking T3 it's almost impossible to tell how well you convert.

There is a theory that taking T3 improves conversion. But it is just a theory and I don't see how you could prove it one way or the other.

[Teddyandolive]

One theory is that taking T3 reduces TSH and a lowered TSH is, in effect, among other things, a signal to downregulate the conversion of T4 to T3.

So, yes - the amount of T3 we add to our T4 can impact the conversion rate of that T4 to T3.

And this seems to be my experience of adding T3

[joey82 in reply to Teddyandolive]

thank you both. I have just compared my only two Rt3 tests I've ever had done on combination therapy.

125t4 / 10t3 = RT3: 0.17ng/ml

100t4 / 45t3 = RT3: 0.13ng/ml

So my Rt3 was less on the higher dose of T3. I know many things can impact Rt3 but I thought these results were interesting, and Greygoose's theory stands correct in this case.

My TSH was heavily suppressed in both blood tests.

[Teddyandolive in reply to joey82]

With a suppressed TSH and altered doses of not just T3 but also T4, it’s difficult to see how any conclusions can be drawn there.

Altered doses of T3 taken alongside a steady dose of T4 would surely prove more informative?

As with all things thyroid related though, we all seem to differ.

For me, adding T3 demonstrably reduced my TSH without altering levels of FT4 or FT3 - suggesting a reduced bang for my buck when it comes to the amount of T3 derived from my Levo

[joey82 in reply to Teddyandolive]

Teddy, you are correct, and I agree. Not much to be taken from here.