TSH 1.5 but T4 1.2 (low)

[helenhenry]

If my TSH is normal (1.5), but my T4 is low (1.2), is it possible that I have hypothyroidism?  I have some symptoms, such as inability to lose weight and lack of concentration.  I read that normal T4 starts at 4.5.  Is that correct?

[AR-10]

There are two different T4 tests, and maybe fifty different lab ranges used by various labs across the globe.

There is a Total T4 test, and a Free T4 test. The Free T4 test is more acurate, but you still have to look at the results in relation to the lab limits on the test report.

My lab uses a range of 0.58-1.64 on the Free T4 test, and 1.2 would be acceptable. Your test results need to be interpreted based on your lab report.

A free T4 test may be listed as Thyroxine - free, or T4 - free, or FT4.

A Total T4 test is often listed as T4 - total, T4, or Thyroxine - total.

[estrelinha]

It's very confusing about those values, a T4 of 1.2 as AR said must be a free T4 and that's a normal value...., when you said that normal T4 starts at 4.5 it's correct for a TOTAL T4 not a free T4, so what are your  Lab references???