How Important is FT3? Elaine, Others?

[Guest guest]

Hi Barb,

The lab tech may actually be a phlebotomist, that is, someone who draws blood,

or they may be a lab assistant.

And many labs don't do the TSI but send it to reference labs.

FT3 is important because many patients with GD produce more T3 than T4 or they

convert T4 into T3 at a faster rate. And while we have less T3/FT3 than we do

T4/FT4, we could have a high or low FT3 that is causing symptoms. T3 is also

more potent than T4.

A better question is: why is your doctor running the T3 uptake when it's an

obsolete test. It does not measure thyroid hormone. T3 is used as a reagent;

it's added to your blood to see how well your binding proteins hook up with

thyroid molecules. At one time we had to do this test to calculate about how

much Free T4 someone had. Now that we have tests to directly measure FT4, the T3

uptake is considered obsolete. Most labs no longer run it. Same with a thyroxine

(T4). There's no need for a T4 if you're having an FT3.

Hopefully, now that patients are asking questions, this will generate some

interest among doctors. Many docs are used to running the tests that were out

back when they trained, and they don't really understand their meaning. some

docs mistakenly think that the T3 uptake measures T3. Good luck, Elaine