So, long story short(ish). (More in my bio). Diagnosed as hypothyroid after many years battling with a 'mystery illness'. Primary hypothyroidism diagnosed via ultrasound and secondary hypothyroidism diagnosed by multiple NHS and private blood tests over a period of a year.
Trial on levothyroxine 50 mcg by GP in June 2024. (NHS endocrinologist still adamant not thyroid problem). Private endocrinologist (specialist thyroid) believes central / secondary hypothyroidism. Told me to immediately double dose to 100 mcg.
Been on 100 mcg levothyroxine for five weeks. Feeling great improvements - energy, skin, eyesight, digestion - the lot. Best I've felt in a decade. Feel this vindicates the diagnosis of hypothyroidism. Definitely not hyperthyroid on this dose and no side effects.
Having my follow-up appointment with private endocrinologist next week so had blood tests at the GP surgery but also decided to have private blood tests at a clinic near me.
I've been using this same private clinic and having occasional NHS tests over the last year. There is a pattern of the NHS tests being different to the private clinic test results. The private clinic uses a lab that is also used by the NHS.
The NHS blood test results have consistently shown higher thyroid hormones than the private clinic blood test the differences were not huge but significant enough for me to finally get diagnosis. (I have tabulated all these results and will attach in my bio).
BUT ... Now this! I'm completely shocked by these results. Which is right?! These tests are only one day apart. How do you dose adjust based on these?
NHS fasting 10.30am. 2/09/24
TSH 0.06 0.35 - 4.94 minus 6.3%
Free T4 16.4 9-19.1 73.3%
Free T3 5.2 2.4-6 77.8%
PRIVATE fasting 12pm. 3/09/24
TSH 0.046 0.4 - 4.05 minus 9.7%
Free T4 16 10-28 33.3%
Free T3 5.4 3.5-9.46 31.9%
Absolutely unbelievable! One indicates not to increase dose and the other indicates an increase of levothyroxine is necessary. My GP called me and was about to reduce my dose to 75 mcg. Luckily my private endocrinologist had said in a letter to the surgery that the aim was to get my FT4 to 19 or 20. Obviously, 20 will be outside the range that the NHS blood test specifies above 🙄 The endocrinologist did not mention the range or percentage when saying our aim was 19 or 20.
My GP didn't ask how I was feeling or about my symptoms but I reminded him of the endocrinologist letter. He is leaving me on 100mcg.
I'm seeing the private endocrinologist next week. What do I do about the huge difference in blood test results? I feel like the private tests are more reliable based on my severity of symptoms over the last year and the private blood test results.
How terribly unscientific and what a complete mess the diagnosis and treatment of thyroid dysfunction is! On the face of it both tests show FT4 as 16 and 16.4 - but how different percentage through range and how different the treatment would be! These laboratory ranges are incredibly different. Why?
Which do I show to the private endocrinologist? I feel I need to follow this up but not sure how. I think I should go with how I feel symptom-wise but GPs seem to act on the blood test results alone...
Very annoyed and very confused 😕 This TF blood test madness needs to end. There needs to be standardisation of reference ranges across all labs. *Deep sigh*.
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Agitator23
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Yes. I was a bit concerned about doubling the dose due to what I'd read on here but the endocrinologist was insistent.
It's been a brilliant experience so far. I can't believe the difference. The brands are the same - Teva just a different dose.
The problem is the vast difference between the FT4 reference range used by the GP surgery - 9 to 19.1 - and the private UKAS laboratory, 10 to 28! The pmol/l analysis is almost identical, FT4 16 and 16.4, but the choice of range makes decisions on dosing impossible. How can I be 33% and 77% for FT4 at the same time?
Both tests were just over 24 hours after last dose.
My GP writes "central hypothyroidism" with that punctuation in my medical notes. Not sure why. Still not in my medical record that I'm hypothyroid.
He is listening and he is trying to do the best he can. I can feel his unease at stepping outside his comfort zone. He's also feeling that he's missed this diagnosis for the past decade... He did in that time, however, send me to every consultant under the sun - except an endocrinologist!
One of my FT4 was tested twice by the same lab from the same sample and both had different results (it was via my GP too). It’s not unusual. Hormones and their blood tests are very fickle.
I agree. I'm rather shocked by the choice of reference ranges, though! The actual measurements in pmol/l seem accurate but the choice of range is all over the place 🙄
The results are virtually the same, they simply have different reference intervals. The private lab has very wide intervals which suggests they don't screen their reference population very well. The percent figures shouldn't be used to give a false indication of precision, they tell you more about the reference group than the individual patient.
My GP is going on the NHS lab saying I'm too high and my endocrinologist wants me at 19 or 20 for my central hypothyroidism... I foresee an ongoing conflict!
Your GP is going by TSH because that's what endocrinologists have told them over the years. If your endocrinologist says you have central hypothyroidism then get them to write to the GP saying this and telling them they should disregard TSH.
The tops of the reference intervals for the free hormones at the private lab look to be VERY high.
I'm not convinced that percentages make any sense for TSH below bottom of TSH reference intervals. And my view is that the difference between 0.06 and 0.046 isn't that great.
Rather than appearing as reflecting the known and expected variations between labs, that private lab appears to have extended the top ends of the reference intervals for FT4 and FT3 by a considerable margin compared to other labs.
They might think they have a justification for this, but I am sceptical that their results can be compared on a percentage through range basis. Given that your actual numeric results are fairly similar, that reinforces the appearance of their tops of ranges being high. Possibly unwarrantedly so.
And you are quite right, doctors across the universe tend to talk of targetting numbers without any apparent appreciation of different labs, ranges, etc. I suspect they simply bring to mind whatever they most often see.
If I were you, I'd avoid basing anything on those high top of range numbers. But I would contact the lab and ask them:
What analyser they are using;
What their historical reference intervals have been;
How they justify their ranges being so different to other labs and their advice on how to compare results. (They might duck this with respect to other current results. But if their ranges have changed, it is entirely reasonable to expect an answer with respect to their OWN historical ranges.)
Great idea to contact the lab. I also think 28 as top of the range is too high. I think I'm going to go for the NHS reference range from just a few years back, 9 to 24. They used this in a 2014 blood test I had. However, this situation with ranges now means my private endocrinologist, who wants me to get to 19 or 20, is going to be at odds with my GP who is using the 9 to 19.1 range. (Apparently, for Central Hypothyroidism they try for a higher FT4 than usual).
We generally feel best when on T4 monotherapy when the T4 is up in the top quadrant of its range at around 80% with the T3 tracking just behind at around 70% :
On the NHS test your T3 is higher than your T4 -
do you feel as though your metabolism is running a little fast ?
The Private blood test has your T3 and T4 the right way round but much lower in the ranges.
Maybe start monitoring your blood pressure, pulse and body temperature AM and PM just to try and understand what your body is doing ?
Once the T4 is up / towards, the top quadrant of its range, the accepted conversion ratio is said to be 1 / 3.50 - 4.50 - with most people feeling at their best when they come in this ratio at 4 or under.
So on the NHS test we are looking at a conversion ratio of 16.40 divided by 5.20 = 3.15 :
With the Private test with a T4 at 16.10 divided by a T3 of 5.40 this makes a slightly faster metabolism at 2.98 - say - 3.00 :
So not much of a difference - but maybe you are running a little faster ?
Thank you for the advice. I'm a bit hazy on the ratio side of things. Don't feel I'm running fast. I think I'm naturally nearer the top of the range (whatever that is!) I'll keep a check on pulse and blood pressure.
Just your T3 and T4 results. T4 a bit more percent through range than T3. 70/60 or 80/70 type numbers the wise ones on here are good.
If your T4 is 100% and T3 at 10% your not converting.
How you feel is more important than numbers, glad you are progressing.
I remember being desperate to be well again.
There is a genetic test too for T3 conversion but if your blood levels are bad then it just conforms that you are more likely to be a bad converter. It is not a yes no indicator.
T3 that is measured is not in your cells though. It is all a bit subtle.
Better if your are not autoimmune type I think in terms of chances of not converting well and less likely to have to avoid gluten and even lactose ....
The long and short of it is, neither are wrong and neither are right. The numbers have their limitations so you need to be guided by a series of consecutive tests and symptoms as far as possible.
Other than that, consider them a round about figure and a snapshot in time.
Honestly, as I’ve learned, it’s not worth a second thought. When you need to be certain in order to change treatment, have multiple tests from different laboratories.
At this stage as you have only been on levothyroxine for 5 weeks, those results are almost meaningless.
Thanks. I'm going to stick with 100 mcg for longer and seeing what happens. So, maybe the appointment after next make a decision. My main problem is that my GP is working on a range that's not going to work for me. I'm going to be in a constant loop of saying I'm fine when they test my bloods and use 9 - 19.1.
Yes, I'm taking 28 as too high as top of range for FT4. I'm going with 9 - 24, which used to be the NHS range until relatively recently. Not sure why, who or when that changed.... That makes me 46.7% through range.
I recently had quite different fT4 results from GP, and MonitorMyHealth. I did side by side comparison as i have suspected for a long time that my GP results are tending to exaggerate my %'s when fT4 results are near the top end.
GP : (veinous draw~ NHS hospital lab @Lancaster)
TSH 2.65 [0.57 -3.6]
fT4 15.7 [7.9-14] 128% which is over range enough for GP to consider reducing dose.
fT4 22.1 [12-22] 101% ... dose is quite likely to be left as is.
The blood samples were taken just 45 minutes apart (same day).
(however , unless we are comparing results taken from the same blood draw , we don't really have much of a leg to stand on when complaining about it , as it is perfectly possible that that the fT4 levels were indeed different )
Wow! These ranges and the TFT interpretations from them are really all over the place. My background is in science and laboratory work and I can't believe how unscientific it is. It really rankles. And it's affecting people's lives each and every day.
I want to know who decides the range and why they're always changing these ranges. It is interesting that the NHS seems always to flag fT4 too high through range and wants to decrease dose and not vice versa occasionally. (Unless others know otherwise). Just wondering why that is....
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