It's the Free T4 we need to test because that gives us the most useful information. Free T4 is what is available for the body to use.
The other test is more accurately called Total T4. There are two types of T4 in the blood: Free and bound. The bound T4 is attached to protein carriers that transport it round the body in the blood. The body cannot use that bound T4 until it is freed from the carrier.
The Total T4 test - aka TT4 and just T4 - is just what it says, the sum total of all T4 in the blood: bound and Free.
That said, it's not really T4 that affects how you feel. T4 is basically a storage hormone that doesn't do much until it is converted into the active hormone, T3. T3 is needed by every single cell in your body to function correctly. So, if there's not enough to go round, symptoms can appear anywhere and everywhere.
Just testing TSH and FT4 will not tell you the level of your FT3, so will not always correspond to symptoms. You could have high FT4 but not be converting it into enough T3, so any symptoms you experience will be caused by the low T3.
The NHS will rarely test T3, for various reasons, so it would be a good idea if you could get that done privately from time to time, to see how well you convert.
Thank you Greygoose for taking the time with that. A little like Serum b12 and Active b12 relationship then. So my results all seem in range then…and I’ll continue to keep an eye…much appreciated!
Well, yes, they're in-range. But it's not just about being in-range because the ranges are so wide. It's about where within the range the results fall.
TSH 2.44 (0.27-4.2)
TSH is on the high-side, suggesting that your thyroid is struggling. A euthyroid TSH is around 1.
FT4: 14.9 pmol/l (Range 12 - 22) 29.00%
This is much too low, only 29% through the range. Euthyroid is around 50%.
FT3: 4.5 pmol/l (Range 3.1 - 6.8) 37.84%
This too is low. Euthyroid is usually around 50% through the range, usually just slightly lower thand the FT4. Yours is higher than the FT4, which suggests a failing thyroid.
However, your TSH is not reflecting these low levels - one would expect it to be much higher. What time of day was the blood draw for this test?
Thank you very much for working all of that ..so an effucient thyroid should have higher through range t4 than t3 thank you.. it was done at 7.30, fasting. Fingerprick which took 4 fingers to get blood so not sure if that didn't help!My tsh has been up and down for yrs, up to 6 at one point...them occasionalky under 0.5 another time!
When I look bk on some results to give u a quick tsh overview...
2015-0.42
2016-3.18
2017-4.66/3.21
2018-3.81
2019-3.47
2020-2.54
2[21-1.92
2022-2.57
2023-2.47/1.84
It was 6 somewhere in there,but can't find date of that!
so an effucient thyroid should have higher through range t4 than t3
No, I'm not saying it should, I'm saying it usually does. But there are exceptions to every 'rule', and hypothyroidism is a very individual thing, so we can never say anything is 100% certain. But, as a general rule.
Just looking at a list of TSH results, without the corresponding Free results, doesn't tell us anything much. At best it's only a very rough guide to thyroid status. And, if the pituitary isn't functioning correctly then the TSH is of no use at all.
And it would appear that your pituitary isn't functioning correctly. It is not responding to the low levels of the Frees - either because it has a problem, or because it isn't getting the necessary stimulation from the hypothalamus. This is what we call Central Hypo.
Unfortunately, Central Hypo is considered so rare that it's not even taught in med school. It isn't rare, but if you never test for something, you never find it. And most doctors have never even heard of it, let alone recognise it when they see it.
If you are hypo due to a thyroid problem (Primary Hypo) - Hashi's or other - you will have:
High TSH + low FT4/3
But, if you are hypo due to a pituitary/hypothalamus problem (Secondary/Tertiary Hypo - aka Central Hypo) you will have:
Low/low in-range TSH + low FT4/3
So, that's something to think about/research/discuss with your doctor.
Many thanks again...I see. Well the Dr hasn't mentioned anything about the T4 being lower in range, nor the ferritin at 37 either or mch raised, so I guess it's either keep asking different Drs or as you say research!
Can I ask, aside from a scan? If there are any other ways of sorting out why pituitary gland isn't functioning properly please?
Doctors know nothing about T4 - or T3! - and know nothing about nutrients, so not surprising he hasn't mentioned them. I don't suppose he's even noticed them. Doctor only look at the TSH, I'm afraid, so it's up to you to point them out and insist that there's a problem.
There are many reasons why a pituitary might malfunction. For example, excessive bleeding during in childbirth, a blow to the head, a non-malignant tumour - but that would need a scan. But very often, people never find out why their pituitary doesn't function well. It's just one of those things that go wrong with the human body, cause unknown.
Thank you...I've started a read on Central and it suggests low iodine as a potential cause. I've had an iodine test in past which was very deficient, can I ask your opinion on that please?
Not all iodine tests are created equal. Which one did you use?
I have never heard of low iodine as being a cause of Central Hypo, and I cannot for the life of me see why it would be. Iodine has nothing to do with the pituitary. Can you link me to what you've been reading, please?
That said, low iodine can cause hypothyroidism, of course, because it is one of the ingredients of thyroid hormone - 4 atoms of iodine for every molecule of T4. But you need to be very careful with iodine, and never start supplementing it on your own. It needs strict professional supervision or you can make things a thousand times worse.
Why did you test your iodine? Was it suggested by some sort of doctor?
Hi greygoose, thanks very much for your help and sorry for slow reply.My iodine test was via Genova and 18 ug/L the range bring 100-199.
I remember getting some iodine and putting small amount in water to drink, but didn't do for very long as got a bit concerned the more I read about iodine...so no idea what level is now, just hope I didn't make things a 1000 times worse-?? That was 2017...
I've searched for where I thought I read that info,but no doubt my mistake! I've learnt nos, take a photo as I research, if something is useful,so I know where it came from!
I had a CAT scan for sinuses in past, so guess it wldve shown any pituitary problem from birth? though appreciate anything cldve happened since...
Can I ask, do you think iodine that low should be supplemented please, out if interest? Many thanks...
Thank you...ashamedly greygoose, I can't actually remember if it was a collected urine sample ober period of time , or just from one. Also did an adrenal test at same time there, in which morning was twice the amount it should've been and dhea very tiny amount under which mentions hypothalamic-pituary-adrenal.imbakances. Haven't checked these since though...
Just found littke more info....apparently I did retest iodine 6mnths later & it was 41. Looks like it hadn't improved TSH at time as prior to iodine test was 3.6, and 3.7 after,plus the after was an afternoon test!Looks like Ft4 was 16 prior to.iodine 11 after! Maybe that's why I gave up on that route then went bk to trying to focus on b12 iron side of things as Mch had risen then too. Plus ft4 rose again...
Seems thyroid just keeps swopping abt,so does ft4. Tsh now at 1.5 is lowest its been for long while, but then so is the ft4. Is it usual to keep doing that or just signs of struggling? Thank you...
Thank you...that would explain the jumping about would it? Yes have pinprick tested antibodies quite a lot of times...highest Peroxidase has been is 20.6, but still below range and highest thyroglob is 17, but currently lower than that?
Well, levels do tend to jump around with Hashi's. And not Hashi's people dont always have over-range antibody levels, so it could still be Hashi's. But, as far as I know, that's not the case with iodine deficiency.
Thank you., it says T4 on my NHS App results? I presumed it would say free T4 otherwise? But nothing should surprise me realky:)If so, then can I ask of its normal for free t4 to be able to change quickly please and is it more helpful to be higher in range than mine to allow ample for conversion into T3 as Greygoose explained, providing it can convert ok please? Many thanks.
Thank you, I've been spoilt and greygoose has kindly worked them out too but have made a note of that and must do them myself from now on! Thanks very much...so yes it must be free t4 the Drs checked and not T4 as they recirded! As Jim said.
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I’m fine. Really?
Thyroidectomy or not? Thyroidmegaly and multi modular goiter. 
Teva, Teva, every where, Nor any tab of Venc
Just needing a bit of tlc :)
