Yes, yet another paper that trashes TSH as sole test. Also, further questions the assumption that everyone who is "old" is expected to have laboratory results consistent with being hypothyroid.
The fact is that there are some medics who understand that - but far too many who do not. And labs refusing to do FT4 and FT3 compounds the issue.
Clin Case Rep. 2018 Oct; 6(10): 1953–1957.
Published online 2018 Aug 21. doi: 10.1002/ccr3.1694
PMCID: PMC6186879
PMID: 30349705
Subclinical hypothyroidism or central hypothyroidism—The danger of thyroid function misinterpretation
Oluwaseun Anyiam,1 Billy Cheung, 1 , 2 and Samer Al‐sabbagh 1
Correct interpretation of thyroid function tests is critical to providing appropriate care to patients with suspected thyroid disease. It is particularly important to distinguish central hypothyroidism from other types due to the potential of concurrent secondary adrenal insufficiency and thus the need for immediate steroid replacement prior to commencing thyroxine.
Thanks for posting. Why is it, that doctors who're supposed to be the 'experts' are not expert at all and seem to not read up-to-date research? I also doubt that they are aware of "Subclinical hypothyroidism or central hypothyroidism".
It comes to something when the patients are teaching the doctors. But given that lab staff are also implicated then something needs to be done about their training too.
Just as a good teacher is more than willing to learn from their pupils, so should good doctors be willing to learn from patients. Sadly this so often doesn't seem to be the case. It seems most doctors have too arrogant an attitude to be open minded enough to revise their out of date med school training. I am less condemning of GPs as they have to cover so many aspects of medicine and cannot be experts in anything. But endocrinologists are supposed to be the experts in this field.
Maybe this is my problem ? But I’ve been left to give monthly blood samples and see the endo in 4 monthly increments . After waiting from January 2018 to finally getting an appointment with him in August he still hasn’t come up with a treatment plan
In simple terms what is the difference between subclinical and central hypothyroidism? I've searched but can't find anything that defines it in a way I can understand the difference.
Central hypothyroidism is when the pituitary does not make enough TSH. That, in turn, means that the thyroid is not stimulated sufficiently to make the needed amount of thyroid hormone.
This could be due to injury to the pituitary or failure of the pituitary to grow properly in the first place. Or a tumour.
One step further back, if the hypothalamus does not produce enough TRH (Thyrotropin Releasing Hormone), then the pituitary will not produce enough TSH. Again, several possible reasons.
Sometimes you will see that pituitary issues are called secondary hypothyroidism. Sometimes hypothalamus issues are call tertiary hypothyroidism. Some, very often, they are lumped together as central hypothyroidism.
The classic lab tests show low FT4, often low FT3, and inappropriately low TSH.
In extreme cases, FT4 and FT3 can be very low, and TSH is still not high, or even positively low.
Sub-clinical hypothyroidism is a theoretical state where the patient has raised TSH but (so medics say) has no symptoms of hypothyroidism. Many of us dispute this, especially as the reason for a TSH in the first place was presenting with symptoms!
The classic lab tests show low (or low-ish) FT4, often low FT3, and slightly raised TSH (but sometimes within range - or at least below the magic 10 at which point it often gets treated).
In central hypothyroidism the relationship between TSH and thyroid hormone levels is broken.
The thyroid hormone levels could be anywhere from very slightly low to extremely low. But TSH, instead of being high to extremely high as should be the case, could be anywhere from very low to only a little high.
In subclinical hypothyroidism the relationship between TSH and thyroid hormone levels works, but the interpretation is broken!
The thyroid hormone levels could be from very slightly low to fairly low, and TSH has risen, but not reached the magic number 10 at which some guidelines suggest treatment should commence.
Hi Helvella thank you so much for your explanation but I would like to add that 18 years ago when I was tested for something else my blood test showed TSH 149, t4 and t3 within range. I had absolutely no symptoms of hypothyroidism.
Very high TSH can occur in many circumstances. If your TSH really wasn't that high, the post below links to a paper which comprehensively reviews the known possible causes of interference with tests.
That's a very interesting article which highlights well some of the conflicting information relating to thyroid conditions and the potential implications of misdiagnosis. I'm very tempted to bring this to my next GP's appointment, as a few persons here have mentioned that I should ask about central hypothyroidism. I thought my GP had requested all the relevant tests to check my pituitary function, but I've learned from this article that there's some more that should be done, including checking if any adrenal insufficiency. Apart from the cortisol saliva test available on Medichecks, I can't see any other tests available for adrenal testing that I can order myself.
"Review of his previous results revealed that his T4 checked a year prior to this was also low (7.6 pmol/L) with a TSH within the normal range (2.5 mIU/L). Moreover, his thyroid function had been checked several times during the previous 2 years demonstrating a similar pattern and he had been given the label of “subclinical hypothyroidism,” for which he was not on any treatment. "
"In contrast, central hypothyroidism (CH) is thyroid hormone deficiency resulting from insufficient stimulation of a normal thyroid gland.11 It is rare, accounting for approximately one per 1000 cases of hypothyroidism."
This man was lucky that the lab actually tested his Free T4 at all. After all, his TSH was in range. For most people presenting with this man's symptoms actually getting a Free T4 measurement is virtually impossible if their TSH is in range.
It seems bizarre to me that the authors of this paper can give statistics on the incidence of central hypothyroidism apparently without being aware of any irony in doing so. It is screamingly obvious (and has been for several years) that current medical practice in the UK makes central hypothyroidism virtually impossible to diagnose because GPs either can't get Free T4 and Free T3 tested or it never occurs to them to try. So how can the statistics on the incidence of the condition be even remotely accurate? And with just a TSH in range, GPs are unlikely to refer patients to endocrinology, and endocrinologists can refuse the referral even if one is made.
The only thing that surprises me is that this kind of paper isn't produced several times a week. I did notice that one of the references [no 25 - another case history] for the paper under discussion was this one :
Lessons learnt from a case of missed central hypothyroidism
The paper above was even more shocking than the one under discussion and I'm surprised the patient didn't die :
"The clinical biochemist reviewed this lady’s blood results and elected to add on a free T4 (fT4) and free T3 (fT3), which were found to be <0.4 pmol/L (normal range (NR): 12–22 pmol/L) and 0.3 pmol/L (NR: 3.1–6.8 pmol/L), respectively."
One thing that hasn't been commented on so far in this thread is that the paper under discussion was written by authors who all work for the NHS. The second case study I've given above also refers to a British case. I wonder if such appalling treatment would or could occur in any other first world country. I suspect it would be much less likely.
I would say, from experience, that these things are all too common in a good many countries, irrespective of how 'developed' or how the medical system is funded. There are very few examples of free-at-the-point-of-care health systems in the world of course, but even in insurance-based systems thyroid misunderstanding is rife.
In America, most health care insurers, including Medicare, work under a system called "capitation." Basically, it pays doctors to work under a system whereby the more patients they see that they do little or nothing to treat the more money the insurance company makes (therefore the more money the insurance group (of doctors) is paid. This is not democracy working, it is Capitalism working, which is what the system is, in reality, in America and always has been, from the slave-owning first presidents right up to the idiot we currently have in the White-house.
I note that your linked paper includes this statement:
Written informed consent has been obtained from the patient for publication of the submitted article and accompanying images.
Quite right and proper that it does. I just want to say that if ever I were asked, I would almost certainly agree so long as the paper is freely accessible and not behind a paywall.
Thank You helvella for another Great and Valuable Post . In my personal thyroid journey I learned that many DR's are oblivious as to how to treat thyroid patients . Far and Few *Get It * . Many are not open minded and go by the *Book* Only . And treat the piece of paper instead of the *Patient* I learned that I have to advocate for myself and read as much as I possibly can and join thyroid communities like this Great One where thyroid patients share Great Information . Knowledge is Power .
For people who don't have internet access and ill-informed doctors I do not know how they cope. Probably diagnosed with an anxiety and given medication for it, rather than a Full Thyroid Function Test and not telling the patient of how to get the best results.
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