My TSH is 0.99, T4 is 10.9 (free plasma). I can't find a range for FT4 of 10.9 but result say 'free plasma'. Is it total T4?

[Elsa1509]

I am very confused by the results as if my FT4 is 10.9 isn't that hypothyroid? However, if it is Total T4, I am nearer hyperthyroid. I have had very bad intermittent pain in my thyroid gland and under alot of stress.

[helvella Administrator]

It is unlikely to be Total T4 - almost all tests in the UK are Free T4 rather than Total T4.

You cannot say where a value of 10.9 lies without knowing the reference range. That is because the reference range for FT4 (in particular) various quite considerably from one lab to another.

In order to make proper sense you simply MUST get the reference range. Anything else is a guess.

Also, the units are different for the two tests:

Total T4 is usually in units of nmol/L.

Free T4 is usually in units of pmol/L.

Rod

[Elsa1509 in reply to helvella]

Thank you very much for your response. I will definitely get a reference range now that I know this, but I still can't understand why there are not standard reference ranges.? The one FT4 range I found that was close to this score was 10 to 18 which means I was on the borders of producing too little T4. However, my TSH is ok, so I was confused. Thanks once again.

[helvella Administrator in reply to Elsa1509]

It would be much better if they were standardised. However, for now, they are not.

There are some FT4 ranges which start between 6 and 7 - others start at 12 or higher!

Rod

[Elsa1509 in reply to helvella]

Thanks Rod. I found out the range for my FT4 test and it is 7.5 to 21.1. I've never seen that range before! I guess that means my FT4 is on the low side, but not low enough to warrant further investigation. However, with my TSH at 0.99 I am still not clear if this makes me completely normal, or slightly hypo or hyper? I am thinking hypo. A few years ago my TSH went up very high (to over 7), but I was showing all the signs of a hyperactive thyroid. I never went on meds and it sorted itself out quickly. Recently, I have had bad intermittent pain in my thyroid gland which is why they checked for thyroiditis with this recent test. Anyway, if you are able to clarify my results that would be so good. Many thanks. Roz

[helvella Administrator in reply to Elsa1509]

A TSH of 0.99 could very well indicate you are fine. But an FT4 of 10.9 in that range looks distinctly low.

A TSH of 7 is out of range high - but we see enough people with very much higher numbers. Did you have an FT4 test at that time?

It is perfectly possible to have an inappropriately high TSH which will then cause excessive T4 to be produced and released - hence hyperthyroid symptoms. The cause could be a pituitary issue. Was that ever investigated as a possibility?

Rod

[Elsa1509 in reply to helvella]

Hi Rod. Thanks very much for this. As my high TSH was many years ago and at a different gp surgery, it would be difficult to obtain the FT4 test (if one was done), at that time. It just seems a strange mix in my result of normal/low TSH, but quite significantly low FT4. I just hope it is not a precursor to my thyroid going haywire again. No one ever mentioned pituitary issue, but have done some research in last few days on thyroid results and there is mention of pituitary issues with TSH and FT4 on the low side. Maybe I'll just have to see how things go as my GP said my results were "satisfactory". Thank you! Roz

[helvella Administrator in reply to Elsa1509]

This link:

thyroidmanager.org/algorith...

is to a "flowchart" of what could cause some odd thyroid test results.

The rest of that same site has a huge amount of very heavy-going information!

Rod