T-4 Thyroxine Reference Range units

[minlou7]

Is there more than one type of range

i.e.  value from one lab is 1.870 and reference range is 0.800-1.900
       next month, different lab, result is 9.00 w/reference range 4.50-12.00 ug/dL

Please explain

[AR-10]

Different labs use different ranges for Free T4 and Free T3 tests.

My local lab uses a range of 0.58-1.64 for a Free T4 test.
The lab my Endo uses (in a different city) uses a similar range, but it is not exactly the same.

It's also possible the second test and range you listed is a Total T4 test rather than a Free T4 test.

A Total T4 test is a different test than a Free T4 test.

I have seen Free T4 tests that use a range similar to the second example you gave, though.

The first test result and range you list is a Free T4, without doubt.

The reasons there are different ranges used are several; type of machine used, how the test is processed (on the equipment being used), and a little bit of "what range shall we use?" in meetings, which throws a bit of arbitrariness into the mix. Different manufacturers of the machines calibrate them in different ways, and I imagine there are factory recommendations on what range should be used with their equipment, as well.

[kitty9309]

Wow- AR! I thought I was the one who worked in the lab! I think you are onto a new career.

I agree with AR and could not have said it better. I especially like the "what range shall we use?" comment!

I was also thinking that maybe one of those tests is a free t4 and the other a total, like he said.

[AR-10]

I learned it from you, kitty.
:o)
Thanks for checking my reply.
Wanted to be sure it was correct.

[Tihow]

My last results were: T4 = 14; TSH = 3.2 I also have thyroid auto-antibodies.

It's all gobbledegook to me and I'd love to know if these results are normal or not.

Thanks

[Barb135]

As noted in posts above, different labs use different ranges and some even use different units of measurements for T4 and T3.  

Your TSH is slightly over the range of 0.3-3.0.  I can't say about the T4, because you don't say if it's Free T4 or Total T4, nor do you give the lab range.  

If you will repost with the lab range, that would help members comment more fully on your question.