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# Can I suppose low T3 from a high RT3 level?

Created October 10, 2011 at 3:24 AM

Thanks to the excellent discussions going on about high LDL both here and at http://perfecthealthdiet.com/?p=4457 I have been prompted to get further thyroid tests to see if that is part of the cause for my extreme LDL.

Despite my doctor's reluctance (given my normal TSH) he requested a test for RT3, fT3 and fT4. What came back from the lab was yet another TSH and RT3 (no fT3 or fT4).

The RT3 came back as 467 pmol/L (range 140-540)

After much googling but with limited success I think I have pieced together that despite the lab range the RT3 result is off the chart. Am I correct?

From what I gather the important thing is the ratio of fT3 / RT3 in that it should be 20 or greater. From what I have found a normal fT3 result is 4.0 ??? 8.00 pmol/L. If that is the case then I doubt my fT3 is going to be 9340 (required to get the 20:1 ratio).

Is my logic so far sound? If so, do I need to bother trying to have another blood test for fT3 or am I safe to assume I've found the problem? I don't fancy having to convince my doctor I need an fT3 test now given he would say my RT3 is in range.

Thanks everyone.

(18696)

on October 11, 2011
at 02:18 AM

That's annoying. Good luck!

(203)

on October 10, 2011
at 09:28 PM

Brilliant. Thanks for the explanation.... looks like I'll need a T3 test now to be sure.

(203)
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(18696)

on October 10, 2011
at 07:00 PM

The oft-quoted ratio of 20 is a bit confusing, because it uses non-similar units. I don't know why they express it like that. You actually want FT3 in pmol/L and RT3 in nmol/L. So the number you would need in your units is 9.34, which is still unlikely, though not as unlikely as 9340.

(18696)

on October 11, 2011
at 02:18 AM

That's annoying. Good luck!

(203)

on October 10, 2011
at 09:28 PM

Brilliant. Thanks for the explanation.... looks like I'll need a T3 test now to be sure.