I know many doctors tell us we mustn't have a suppressed TSH. And that's a story in itself, as many of us taking T3 have a suppressed TSH. And we also know it's the T4/T3 levels that count and not the TSH
BUT - what is the exact definition of 'suppressed'? Is there a paper or link somewhere defining this?
I think I've read somewhere that it's not just a level below the TSH reference range.
I think jimh111 may be able to help answer this. He mentions 'subnormal TSH' in the last para of his comment here healthunlocked.com/thyroidu...
Most doctors would say below range TSH is “suppressed” but 0.49 would be mild suppression and <0.01 = undetectable.
This video was highlighted to me previously & I think it explains it well.
It depends who you talk with!
Even when you get a definition of that, you then see mention of "very suppressed TSH", or "incomplete TSH suppression" or "fully suppressed TSH" or "markedly suppressed TSH". Go back to the start...
“When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’
’The question is,’ said Alice, ‘whether you can make words mean so many different things.’
’The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.”
Which is master?
And, in context, is it the level of TSH that matters? Or the levels of thyroid hormones which result in those levels of TSH? Hence, if the TSH to thyroid hormone linkage is broken, does TSH mean anything at all?
I imagine someone who has no thyroid but good levels of T4 and T3 (due to tablets, of course) and seems perfectly well. But, because their TSH is low you decide to inject TSH hormone. It cannot have any impact on the non-existent thyroid. But are they any better off having non-suppressed TSH?
The following are quoted strictly for the precise wording re TSH suppression. Not for any merits of the papers quoted in themselves.
Suppression is defined as a level below the reference range, and there are several different levels of TSH suppression: Mild suppression: 0.1 to 0.5 mU/L. Moderate suppression: 0.1 to 0.01 mU/L. Severe suppression: below 0.01 mU/L.
palomahealth.com/learn/pros...
TSH levels below the normal range, maintaining normal levels of serum free T4 (FT4) and free T3 (FT3). Based on TSH levels, suppression is mild when TSH is maintained between 0.1 to 0.5 mU/L, moderate when TSH is maintained between 0.1 mU/L to 0.01 and severe when TSH is below 0.01 mU/L.
ncbi.nlm.nih.gov/pmc/articl...
A suppressed TSH is a way to refer to a condition in the body in which the TSH is lower than it should be under “normal” conditions.
TSH suppression occurs as a result of taking too much thyroid medication but is also secondary to certain medical conditions which cause hyperthyroidism (such as Graves’ disease).
restartmed.com/suppressed-tsh/
Overtreatment, however, resulting in a markedly suppressed thyroid-stimulating hormone (TSH < 0.1 pU/mL), has been shown to lead to osteoporosis and cardiac toxicity.
jabfm.org/content/jabfp/11/...
The last link refers to research dated 1998…. Perhaps latest research might allay one’s fear regarding cardiac toxicity ? I have a feeling I did read an article suggesting this… but cannot remember where I read it. Sorry it’s not useful. You always seem to be aware of the latest research works.
NIKEGIRL
Read the restartmeds link shared by Helvella 2 comments above :
In fact the whole post is interesting:
Check out the video :
I like this one:
A suppressed TSH is a way to refer to a condition in the body in which the TSH is lower than it should be under “normal” conditions.
Being hypo cannot possibly be classed as 'normal' conditions! Can it?
And does anybody mention the pituitaries role in all this, and the fact that it, too, can be messed up and non-functioning?
Undetectable is another story. If your TSH is undetectable, all your bones will break and your heart will immediately go into AF and you will soon die. Thus spake the numpteys of the endocrine world and their words echo still as they struggle to raise the TSH of so many by reducing doses.
Sometimes they succeed although levels of FT4 and FT3 fall at an alarming rate and their patients struggle to live their lives with any sort of normality.
It would appear that this is irrelevant as long as the objective has been reached.
“Whoever said ‘Winning isn’t everything’ was not fighting Hypothyroidism”
Anon
Historically "suppressed" is used to mean a TSH that is below the lower limit of detection with a tacit understanding it didn't apply to central hypothyroidism. This became increasingly meaningless as assays became more sensitive. So, a TSH below e.g. 0.5, 0.1, 0.05, 0.01 might be definitions if "suppressed" as time goes by.Doctors still use the term "suppressed" to refer to a TSH that is either below the lower limit of detection, or below the lower reference limit. Two quite different levels.
I dislike the term "suppressed" and prefer to refer to a "low TSH", at least until we are sure whether it is low due to genuine suppression or insufficient secretion from the pituitary.
I see lots of people on the forum with low normal TSH, fT3 and fT4 (all three). This is not normal, it's not really central hypothyroidism so I call it subnormal TSH secretion. This can happen when there has been a period of thyrotoxicosis from e.g. Graves' or taking too much hormone.
There is evidence that TSH stimulates deiodinase. So, if you have subnormal TSH secretion you will have conversion problems. and a little thyroid hormone will push TSH down even further reducing conversion even more. I don't believe T3 always suppresses TSH, it depends on the dose. However, many of the patients who need T3 have a subnormal TSH that will fall more rapidly than normal. This could give the impression that T3 suppresses TSH
Tony Bianco is giving a talk at the Thyroid Trust in London in November, I will try to kobby him to do research into TSH stimulating deiodinase as I think this js much more important than most doctors assume.
So the story about the thyroid/body being able to "decide" to secerne more T3 than the usual ratio (10:1?) to preserve T3 levels, is actually about the increased deionidase promoted by the high TSH?
A high TSH gets the thyroid to secrete proportionally more T3 and of course this can't happen if the thyroid is kaput. A higher rate of deiodinase within the thyroid and other tissues contributes also. This is one reason I feel a subnormal TSH is bad news and it is so often overlooked.
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