Normal TSH low T3 - initial diagnosis / lab error?

[muppetme]

When I first had hypo symptoms (raging hypo, and I knew what it was, but GP's said not) my T4 & TSH were normal, but my T3 was borderline bottom of the range. It was another 9 months or so, with worsening symptoms, before my TSH went above the range, my T4 started to drop and I had both types of thyroid antibodies.

My results in July 2018 were:

T4 15.7 (range 11.0 to 26)

T3 3.8 (range 3.9 to 6.8)

TSH 4.11 (range 0.35 to 4.5)

I now believe that those initial results showed I had poor conversion, hence the raging symptoms - is that correct?

Am I right to say that my TSH was still normal at that time because it was registering that I had enough T4.... hence TSH would seem to be completely irrelevant as a method of monitoring if poor conversion is the issue?

Does a TSH measurement distinguish between T4 & T3 in any way?

I am looking for ammunition to take into battle for my next endo appointment - is there a relevant piece of scientific literature on the pointlessness of a TSH measurement in the face of what I believe is poor conversion?

(I source my own T3 & take in combo with T4 - I've been stable for 5 years. I'm going back through my history to see if I can make a persuasive argument so my endo prescribes T3 without first having to take me off it to prove I need it 🙄)

Separately, second question:

I had follow up tests in September 2018 -

T4 16.2 (range 11.0 to 26)

T3 4.6 (range 3.9 to 6.8)

TSH 3.89 (range 0.35 to 4.5)

When I first received this second set of results I received them in a typed letter so I had for a long time assumed that the T3 & TSH results had been confused and were the other way around (ie. just above range TSH & borderline low T3) as that would have been consistent with the initial July results. I have since obtained the original lab report (Nuffield Health) and it shows the stated results which don't appear to be consistent.

Is there any way that the lab could have got the results confused & the wrong way around? Is reporting of results automated (and therefore likely correct), or manual & therefore subject to potential human error?

[TiggerMe Ambassador]

The way I'd read the first results suggests a feedback loop issue as both fT3/4 are low and the TSH doesn't really reflect that... ratio isn't terrible just not enough of either and often when there is a shortage the body creates more fT3 to survive

TSH 4.11 mIU/L (0.35 - 4.5) 90.6%

Free T4 (fT4) 15.7 pmol/L (11 - 26) 31.3%

Free T3 (fT3) 3.8 pmol/L (3.9 - 6.8) -3.4%

T4:T3 Ratio 4.132 

You say you have both raised antibodies which means your results could be all over the place depending on autoimmune activity.... but are actually surprisingly similar

Better levels...

TSH 3.89 mIU/L (0.35 - 4.5) 85.3%

Free T4 (fT4) 16.2 pmol/L (11 - 26) 34.7%

Free T3 (fT3) 4.6 pmol/L (3.9 - 6.8) 24.1%

T4:T3 Ratio 3.522 

A functioning thyroid does produce fT3 and fT4 so it's more important to look at conversion when on levothyroxine only