Free T3/T4

[Minimouse1]

Hi, could someone explain why my doc should do free T3 & T4 as well as the usual T3 & T4 - or is it included as part of the same test?? I'm taking 100mg of levo for hypo (hashis), but my doc hasn't yet tested for T3 although he will do so in my next blood test. I was wondering what the free T3 & T4 is about??

[greygoose]

You have two types of thyroid hormone: Free and Bound (to carrier proteins). The Free hormones are the ones your body can use straight away. Those bound to carrier proteins have to be unbound first.

So, you have two types of tests: FT4/3 and TT4/3 (sometimes just written as T4/3). FT4/3 tests the Free hormone available for your body to use - which is the most important to know. TT4/3 stands for Total T4/3, and it tests all the T4/3 in the blood: Free + Bound = Total. So, with the TT4/3 test, you have no idea how much hormone is available for the body to use, and how much is still bound to carrier proteins. So, the TT tests don't give you much useful information - especially not the TT3 test.

[SeasideSusie Remembering]

As you are in the UK, it's very likely that Free T4 and Free T3 are the tests that would be carried out. England and Wales do those, I think I've seen results from members in either Scotland or Ireland that show Total T3.

Your GP may ask for Free T3 to be tested, but it's the lab's decision as to whether or not it is done, they often only do it if TSH is suppressed. I'm in Wales, my TSH is always suppressed and my FT4 and FT3 get done every time, but that doesn't mean to say that every Health Board will do the same.

[Minimouse1 in reply to SeasideSusie]

My GP sent a request for advice to the endo consultant at the hosp. The consultant replied saying I was not on enough meds yet & that they should increase levo, then re-test in 6-8wks with T3. So that's why I'm expecting them to do this.

[AmandaK in reply to SeasideSusie]

What happens if the GP/endo poo-poos the testing of FT3, as I've experienced, stating that it isn't a useful test and is unreliable? Others might experience the same so need to be prepared as to how best to respond.

[SeasideSusie Remembering in reply to AmandaK]

My GP poo-poos everything except TSH. She's one of the "TSH is the only test that matters" robots. I don't know how we educate them. I just ignore my GP, dodge as many tests at the surgery I can, and I've sorted myself out and do my own tests to keep an eye on my levels.

[AmandaK in reply to SeasideSusie]

Minimouse1 seems to have a much more enlightened GP, which is rare!

[SlowDragon Administrator in reply to AmandaK]

But lab is still likely not to do FT3 test!