I have just recently had a blood test undertaken at a London Hospital - where my levels of T4 have halved but TSH has stayed the same. I now see that the consultant has requested another test (at a totally different hospital) which has come through entitled - Thyroid Interference test - where the levels have dropped again.
Can I ask is this test due to the original lab having a problem with their equipment - or are the consultants looking for something else - it is strange that the TSH has not risen and I am suspecting as I mentioned to the consultant - Atrophic Thyroiditis - where an antibody blocks the TSH getting into the cells. Any ideas - would be grateful. Many thanks.
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posthinking01
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Some analysers are affected by factors which do not affect other analysers.
One classic is if you have antibodies to TSH. Some analysers seem the combined TSH+antibody (called macro-TSH) as if you have lots more TSH than you actually have.
There is the potential to have antibodies to T4, T3, mouse (which matters in some cases), and several others.
Another classic which has only been appreciated in recent years is high levels of biotin - often from people with multiple sclerosis who have been trialling biotin against MS. That can make some results appear high, and others low. And varies by analyser.
So it isn't something wrong with the specific analyser machine - but with every analyser which uses that technique.
Of course, machine issues are theoretically possible. But interference is when a factor causes results to be affected.
No, I doubt the original lab has a problem with its equipement. Just with testing your blood. Your blood could contain antibodies that don't react well with the testing method, so he has requested testing at another lab, with another testing method, to be sure. I know this isn't exactly the same as your problem, but diogenes explains it in another post:
There are about 8 major suppliers of diagnostic tests for thyroid. They can use several different methods to produce the test result. Some of these have a problem if a patient has antibodies (say against mouse and sheep proteins) pre-exsting the blood. These can artificially raise the TSH measurement by interfering in the test. In a case where a patient has normal to high-normal FT4, and high TSH, these circumstances should be examined by measuring by several methods. Such a combination is very suspicious,
it is strange that the TSH has not risen and I am suspecting as I mentioned to the consultant - Atrophic Thyroiditis - where an antibody blocks the TSH getting into the cells.
I think you may have got a little confused, there. Not sure I can sort that out. Which cells do you mean?
TSH is a pituitary hormone that stimulates the thyroid to make more hormone when the pituitary senses low levels of T4/T3 in the blood. It doesn't affect any other cells in the body. A TSH test just detects the amount of TSH in the blood.
Atrophic Thyroiditis, as I understand it, is like Hashi's without the goitre - it's what I have. And, my TSH pretty much always corresponds to my thyroid hormone levels in my blood.
I wonder if you're confusing it with Central Hypo, where the pituitary doesn't react to changing levels of thyroid hormone in the blood for some reason - and there can be several reasons. They are two different diseases.
Hi there thanks for reply. This is what I mean that the antibody would not allow the TSH to reach the thyroid - I perhaps used the wrong word in cells but there again this would need to get to the cells eventually.
You are right that TSH receptor blocking antibodies would prevent sufficient TSH getting into the cells of the thyroid and stimulating production and release of thyroid hormones.
A simplistic approach would expect TSH to rise if that were the case. But Tania Smith does explain that TSH can be detached from T4 and T3 levels.
This is NOT what an interference test is about. You need a TSH receptor antibody test. Ideally one which can see the difference between stimulating, neutral and blocking forms - which is not common.
OK, I see what you mean. But, if that were the case, the TSH would be high, not low, compared to thyroid hormone levels. So, I don't see there's a connection between Atrophic Thyroiditis and your problem of TSH not rising. The TSH test does not test what's got into the cells, but what is in the blood. And, your problem would appear to be more with the pituitary not reacting to thyroid hormone levels, and therefore Central Hypo.
But if TSH is being blocked by an antibody then maybe it would not rise as the system not working properly - bit confusing I must say - but that is how I read it - that TSH is not getting to the thyroid or at least not showing in the blood test results which has happened to me for years - my blood were always Ok but they weren't - they were being hit by an antibody not showing the true picture. When I hear from the consultant I will let you know so we can put out the info.
Your problem is not that your TSH is not getting to the thyroid, but that the pituitary is not making enough of it in line with the level of thyroid hormones. If the problem was that the TSH wasn't getting to the thyroid, the FT4/3 would be much lower and the TSH much higher. I think that, with your line of reasoning, you're in danger of confusing your consultant! lol
TSab ~Stimulating ones, fit into the TSH Receptors on the thyroid , where they act just like TSH and stimulate the thyroid, causing T4/T3 production to rise. (while TSab dominate, you get Graves Hyperthyroidism, with high T4/3 and low TSH)
TBab ~ Blocking ones, fit onto the top of TSH receptors on the thyroid (like a cap), so they block any TSH from acting in the TSH Receptors, the thyroid then lowers its T4/T3 production. TSH production continues to rise in response to the low T4/3 ( while TBab dominate, you get Hypothyroidism, sometimes called 'Graves hypo' , with low T4/3 and very high TSH )
If an untreated (no levo) hypothyroid person had large numbers of TBab that were blocking their TSH from acting on their thyroid.. then you would expect to see: Low T4 /3 And VERY HIGH TSH ~ because the hypothalamus /pituitary have detected the low T4/3 levels and are producing more and more TSH in response .... but that TSH still can't get into the TSH receptors on the thyroid, so the T4/T3 stay low ....and in response the hypothalamus /pituitary continue to make TSH go higher and higher... ( i'm still struggling to figure out what would happen in a treated person who got loads of TBab . but probably their results and dose would go all over the place as their levels of TBab fluctuated)
Many currently used tests for TRab count both stimulating and blocking antibodies and the 'result' is both 'TSab and TBab added together', but they are more sensitive to the stimulating sort, and not so good at counting the blocking sort. They were designed to test mainly for TSab (to confirm Graves Hyper).
One older method of testing TRab is called a TBII test (not commonly available in labs anymore) .. this also counts both stimulating and blocking , but is much better at counting the blocking ones... so a very high TBII result means lots of TBab were counted, and this coupled with low T4/3 and very high TSH, is the biggest clue to someone having high levels of TBab.
A TSI (Thyroid Stimulating Immunoglobulin) test, counts ONLY the stimulating sort (TSab)......but I don't think there is a commercially available test that can count ONLY the blocking sort (TBab)
The lack of a goitre does not necessarily mean we have lots (or any) of the blocking sort, but i think they are more frequently found in 'atrophic' patients than 'true' hashimoto's patients.
... to suspect TBab were involved ,we would also need to see a history of fluctuating and very high TSH levels (and preferably a very high TBII result).
But TBab can be hard to catch unless testing is done at the right time... levels of TSab and TBab fluctuate .. if you have both ,then whichever is dominant at the time will have it's effect... either Hyper or Hypo.....and for long periods of time they may even balance each other out.. making it look like you no longer have a thyroid problem.
So if you want to know if you have TBab then you need to find a lab that can still do do a TBII test (Thyrotropin-Binding Inhibiting Immunoglobulin ) AND test when they are high! ....this post is from someone who has has apparently(?) had one recently , but i don't know where they live . Bhattinsami healthunlocked.com/thyroidu...
TBab are not the sort of antibodies they are looking to rule out in an 'interference' test .. these can be eg HAMA (Human Anti Mouse Antibodies) !
Full explanation of what they are looking for in 'interference tests' is here :
" Funny thyroid function tests - avoiding the pitfalls… - RCP ... rcplondon.ac.uk › file › download PDF Mark Gurnell. University of. Cambridge. Cambridge University Hospitals. NHS Foundation Trust. "
Copy the above into search engine (without the "s ) to download a power point presentation used for teaching.
(some of it is to do with proving noncompliance with taking meds , but a lot is to do with antibody 'interference' or other causes of incorrect results )
This paper explains the same stuff in written form:
Hi there - thank you for that - I know when I try to find answers for people in trouble it takes a lot of time - so I thank you very much - this is very very useful. As my TSH has NEVER been high - I am now wondering what the heck is going on. I still haven't heard from the consultant who by the way is my Lupus/Renal consultant - trying to help me hit endocrinology with tests to prove my symptoms ARE endo related.
You're welcome . i had to try and get my head round TBII testing yesterday for someone so i thought i'd write it out again while i still remember what i think i know ... as it will have gone fuzzy again all too soon. Hopefully the interference testing will prove helpful in some way... fingers crossed.
p.s . you should also add a "probably" , "usually" or " in theory" in front of all of my "very high TSH " comments because real life is way more messy than nice neat theory.
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Which cells do you mean? 
Will this interfere with my underactive thyroid?
Testing tomorrow - DHEA interference?
Antibody interference in thyroid assays: a potential for clinical misinformation
Thyroid function tests 
Assay’s interference 
