FT3 T3 and FT4 T4

[aptucxet]

I am having my blood tested in a few days and would like to know which is more important to have tested ..........the "free" versions of T3 and T4 .........or just T3 and T4. Thank you very much.

[Lalatoot]

The frees. Free in non scientific terms means it is available for use by the body and cells.

[aptucxet in reply to Lalatoot]

thank you, but I want to know which is more important to have tested....... FT3 or just T3

[Lalatoot in reply to aptucxet]

The frees are the ones to test - that is free t4 FT4 and free t3 FT3.

[aptucxet in reply to Lalatoot]

OK.......and thanks very much. So I will have FT4 and FT3 checked..........

[Lalatoot in reply to aptucxet]

Yes. Those are the useful ones.

[helvella Administrator]

The total versions are strongly influenced by the amount of binding proteins in the blood.

Factors that influence those include, for example, oestrogen. Thus total tests are affected by these same factors.

And bound T4 and T3 is simply not available to be transported into cells.

Therefore it is the free tests that are relevant to thyroid hormone getting into cells.

(As with everything else, some will argue that total tests have their uses, or even that in their view, they have advantages.)

[aptucxet in reply to helvella]

Sorry, I'm still confused........which is MORE important to have tested .........FT3 or just T3

[helvella Administrator in reply to aptucxet]

it is the free tests that are relevant to thyroid hormone getting into cells.

If T4 and T3 are not free they cannot be transported into cells. Therefore they are largely irrelevant.

(In the UK, people very often just refer to T4 and T3 because almost always, it is the Free tests that are performed. And therefore often specifically say Total and not just T4 and T3. But it is possible to misinterpret posts because of this.)

[aptucxet in reply to helvella]

OK.......I know I'm a little dense with all the tehcnicals .......but understand that FT4 and FT3 are the ones to have tested. Many thanks