Is a suppressed TSH harmful to health?

My TSH has been suppressed over the last couple of years to keep my T4 levels at the upper end of the reference range throughout two pregnancies (it's normally in the region of 17-18). My TSH has been circa 0.01. I was taking 125mcg Thyroxine and feeling well. Since having my baby in April my dose has been reduced to 100mcg and I still feel well (latest results TSH 0.05 and T4 17.7). I have a telephone app booked in with my GP on Thursday and I know she will tell me to reduce my dose as my TSH is 'too low' and I'm now at risk of osteoporosis etc.. My question is, does anyone know if a suppressed TSH is bad for you? I was only diagnosed as having Hashimoto's in early 2011 and have only felt well when my TSH has been suppressed and I have been at the upper end of the T4 reference range. I don't want to reduce my dose now when I feel well? Any advice/thoughts would be much appreciated. Thanks...

15 Replies

  • Iam curious about your ft3 lvls are they in the upper range too?......i dont know the answer to your question......t3 is an active hormon, t4 has its benefits too, some said for the brain etc and it converts mostly in the liver to active t3 but in other tissues as well, localy, so it is relevant.......if you are feeling good with t4 therapy only consider yourself lucky:-) and not so ill......

  • Thanks for your reply. I don't know what my T3 levels are, I've never been told them. I suppose as I've felt well, I've never investigated T3, but I do know this is more important. I take it these aren't checked as standard (T3 that is) when thyroid function tests are done by the GP, I think it's just T4 and TSH that is looked at routinely? I might bring up the subject of T3 then if a decrease is suggested but I can already imagine how that conversation will go!

  • Just freaking amazing, how can anyone exclude ft 3 which is the ACTIVE one:-) and every doc knows this...and i would even agree they exclude it if they can explain to me the link between ferritin and t4 and how t4 converts to t3 and why i have lower ft3 now then before taking t4......i have not found any answer to any of the excluding active hormon from labs just amazes me:-)

    In the end i think they feel helpless , they dont give combined therapy here in croatia! So no reason to measur eit if there is no help for it...this sort of reasoning can only explain why overlooking the ACTIVE hormon!

    Endocrinology is in stone age!

  • Ivy, I would disagree that every doctor know that T3 is the active hormone. My doctor - Henri - doesn't even know what T4 is! I tried to explain to him about T4 and T3 and he just brushed it aside. "All that is for hyperthyroidism, not hypothyroidism!" he bellowed. lol

    I know he's a dinasaur, but I'm sure he's not alone. There must be a lot more like him out there!

    But it would seem that in England - I live in France - it's the labs that decide what tests they are going to do, not the doctors. And I doubt they know much about the subject! It's a strange state of affairs when laboratories are a law unto themselves and can over-ride the doctors orders. I just don't understand why those bullyboy doctors put up with it. They're quick enough to tell their patients what's what, why don't they do the same to the labs!

    Hugs, Grey

  • My understanding is that if your FT4 and FT3 levels are within range, then a suppressed TSH is not an issue.

    This is the issue I have with my GP, who wanted to reduce my dose when my TSH was suppressed, but my FT4 was only 14.1 (9-26). I refused. In fact I increased it by another 25mcg and now my FT4 is 24.8 (9-26), my FT3 is 5 point something (2.8-7.1) and I am feeling very well.

  • This is my goal those sort of ft3 ft4s i think we should all share our numbers and feelings with it and we may come to conclusion that your numbers are the goal!! Lucky you:-)

  • My husband takes NDT and has done for 8 years his TSH is non existant /totally supressed

    he also has central hypothyroid so it would be very low anyway

    Since he is a pretty fit 72 yr old who had had graves then Hashis from youth i reckon a supressed TSH cant be harmful

    For him and our daughter and grandaughters its levothyroxine and T3 that are imeasurably harmful

  • There is a great deal of information on TSH testing at

    -- see Current best method to diagnosis ---"Simply relying a TSH to determine the thyroid status of a patient demonstrates a lack of understanding of thyroid physiology and is not evidence based medicine"

    You could print this off for your GP. Beware, there are 118 references!!

    Good luck with your GP.

  • This is sooo good article!! Thank you bomap!! I can not even test reverse t3 in my country they dont measure it lol:-) ......the only thing i miss in the article is what therapy they use what sort of t4 /t3 ratios, from some naturopath docs i heard it can even be 2 to 1 ratio! My doc gave me 4 to 1 now , eagerky waiting for tablets to arrive, and will report

  • You are most welcome.

    The Deiodinases section on can explain it much more succinctly and better, than I can. Look under Deiodinase type II (D2) where they quote --

    “Changes in pituitary conversion of T4 to T3 are often opposite of those that occur in the liver and kidney under similar circumstances. The presence of this pathway of T3 production indicates that the pituitary can respond independently to changes in plasma levels of T4 and T3…Given these results, it is not surprising that a complete definition of thyroid status requires more than the measurement of the serum concentrations of thyroid hormones”.

    If any tells you that the article is too old remind them of “Doing New Research? Don’t Forget the Old, Nobody should do a trial without reviewing what is known” by Mike Clarke. Citation: Clarke M (2004) Doing new research? Don’t forget the old. PLoS Med 1(2): e35.

    Happy reading.

  • No, a suppressed TSH isn't 'bad' for us. If we feel well our dose should be left as it is. Even Dr Toft of the British Thyroid Association says in an article from a Pulse Online article:s:-

    The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range – 0.2-0.5mU/l.

    In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.

    But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.

    This ‘exogenous subclinical hyperthyroidism’ is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l).

    Even while taking the slightly higher dose of levothyroxine a handful of patients continue to complain that a sense of wellbeing has not been restored. A trial of levothyroxine and tri-iodothyronine is not unreasonable. The dose of levothyroxine should be reduced by 50µg daily and tri iodothyronine in a dose of 10µg (half a tablet) daily added.


    If you read the second question (as well as the first) on this link:-

  • Adoc, TSH 0.05 is low but not suppressed ie 0.03. This study finds no significant impact on bone mineral density levels from low TSH.

    If your GP expresses alarm because your TSH is below range offer to have a Dexa scan to check BMD and an ECG if atrial fibrillation is mentioned.

  • Just to say that my wife's TSH has been suppressed for 45 years on T4 only, after a Hashimoto attack, without incident - slight AF occasionally now but that's normal at 75! Her FT4 was always around the 20-22 mark when it was measured but the hospital only does TSH now so we don't bother testing any more.

  • My TSH was 0.01 for about 12 years and I'm still alive and kicking! Well, alive, anyway. Can't lift my leg high enough to kick! But what do you expect at nearly 70! lol

    Last test it was about 0.45 (due to unavoidable circumatances my TSH went up to about 39 at Christmas) and my doc was already having kittens, wringing his hands and wailing 'you're hyper, you're hyper'. When I said so what, he went into sulk mode and said I could do what I damned will liked, it was no skin off his nose! lol

    It's probably back down to its usual 0.01 again by now because I upped my dose after that.

    Hugs, Grey

  • I'm Hyper and I've had suppressed TSH levels since 2008 (less than 0.01 for 6 years now) and will continue with my anti-thyroid meds long term. I've been told that it unlikely to affect my bones joints etc - but I must say that I've had joint probelms since my late teens so not linked to Thyroid issues. I've had some tests recently for arthritis etc and was all clear.

    The best indicator is how you feel, and being lucky enough to have a decent Dr that's able to hold a conversation with you.

    Good luck x

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