FREE T3 AND FREE T4

Hi,

   Could someone explain what Free T3 and Free T4 are.  I had my blood work done as advied by the board T3, T4 and TSH.  Is there a difference between T3 and T4 and Free T3 and T4?  Is that what is actually produced by the thyroid?

Liz

[AR-10]

T3 and T4 are hormones. The thyroid manufactures and distributes them along with T1, and T7, and some other Ts as well. Hormones that your body uses. The T3 is absorbed into cells, and the T4 is converted to T3 as needed.

A lot of the T3 and T4 get bound up while in the blood by enzymes or something small and pertinant, and is not available, or useable. Only what the body thinks it might need is left "free" in the blood, to be used as needed. This is a normal regulatory mechanism that eliminates excess hormone.

So measuring Total T4 is very different from measuring Free T4.

Modern test use TSH, Free T4, and Free T3 tests. The "free" tests are considered to be more accurate than the total T4 and the T3 uptake tests.

I think.
I could be wrong.

[stella5349]

You're not AR -- you are totally correct. I wish our doctors treating us could be so informative.

The free T's measured are much more accurate to assist in any problems when a full blood panel is done.

The only thing is the T3/T4 tests help determine if the patient is having trouble with any conversion process.

[Liz1900]

Thanks for the answers on the Free T3 and Free T4.  I got my blood work results and it shows that I am still getting too much thyroid.  Just trying to understand.  Doctor changing me from Armour to Synthroid....hope it works.

Liz