I recall reading somewhere on here that the TSH level when on liothyronine only is not accurate as a diagnosis for increasing/decreasing doses. I have been searching on here for info, to no avail. Can anyone help please.
Is blood test for TSH level when taking liothyr... - Thyroid UK
Is blood test for TSH level when taking liothyronine only skewed?
Written by
DandyButch
To view profiles and participate in discussions please or .
Read more about...
35 Replies
•
Jaydee1507Administrator
When on T3 only one would expect your TSH to be very low indeed to fully suppressed - 0.01. That's just what T3 does as the pituitary no longer needs to call for more thyroid hormone.
So then you need to look at FT3 as you're not taking any T4 so FT4 is also useless.
It's very important to show stable blood levels of T3 by taking your last dose of T3 8-12 hours before the blood test. If you usually take T3 all in one dose then split it the day before the test and take a portion 8-12 hours before the blood draw.
in reply to Jaydee1507
Jaydee1507 May I ask, why do we split the T3 the day before the test?
I take my T3 & T4 as one dose when I wake. I then have my blood draw the following morning before I take my meds again, so I can see my levels at their realistic lowest before I take my medication. Why does forum recommend otherwise?
I can't speak for the rest of the forum but it makes sense to me to capture an average FT3 as opposed to the highest or lowest point.
FT3 after dose
in reply to Jaydee1507
OK, I find that a bit nonsensical but I don’t want to stress either of us out by going into it 😂🙏 I have been collecting my bloods the same way for so long it wouldn’t make sense for me to change my method anyway as none of my comparisons would make much sense now.
Because T3 doesn’t stay stable more than 12 hours in the blood….though it stays in cells longer
Lalatoot in reply to
I don't agree with splitting the dose the day before a blood test. I feel that it gives an unrealistic picture of levels.I try to stick to my normal dosing routine so I can see the levels I really have to work with each day.
As long as you interpret your results in the knowledge of the gap you left between dose and test then all is well.
You are correct in saying you are measuring your levels at their lowest and I'd stick with that.
in reply to Lalatoot
Glad I am not alone in my logic, it would be strange for me to see my bloods when I take T3 at night because I never do that, so I don’t really care to see that result.
I feel consistency must surely be most important above all, as none of my other results would be much use to compare if I changed it up at this stage. I’ve been collecting results for 10 years, T3 has been involved for 3.
Lalatoot in reply to
I dose 6am and 10 pm both for levo and lio. The biggest gap between doses is 16 hours. By accident I fell into a routine of testing levo 16 hours after a dose to give the lowest ft4 and 8 hours after lio dose giving average ft3. I do my test at 2pm as this lets me take my morning lio as normal and I take my levo after the test .
radd in reply to
dfc,
Are you on T3-only?
in reply to radd
No - 150 t4, 20 t3 bith taken in the morning
radd in reply to
dfc,
My pinned post regarding meds and test timings states. ...
'Liothyronine (T3)
Not many are prescribed T3-only, but are self medicating or under the care of a specialist who recognises the effects of T3 on TSH. Therefore, forum suggestions become less relevant' ... healthunlocked.com/thyroidu...
I fully agree with you regarding combo meds.
in reply to radd
My asking was kind of academic but I am glad you agree. If I had to cut up my thyroid-treatment-decision pie it would be symptoms 50%, signs 40%, bloods 10%.
But I’m lucky I feel confident to self-treat if I have to, I don’t have a GP I’m interested in placating.
Hello, thank you for your prompt reply. I am currently on 10mcg x 2 daily. My next endo appointment is at the end of October but I need to book my blood test before.She said I may need an increase.
How long does it take to feel 'normal '
Again. Up until February last I felt like death, fatigued, anxious, depression, brain fog , hair loss,
Insomnia, but exhausted, heavy beating heart when exerting. Etc etc...
I am still experiencing same symptoms, although not quite as bad.
From February to June this year I was on 5mcg x 2 daily. Since June 10 mcg x 2 daily.
Its very variable as to how long it takes to feel normal. There are also other factors such as low/deficient vitamins to consider and get to optimal by supplementing. Have you had bloods done for ferritin, folate, B12 & D3?
Yes, some, but about 18 months ago.I'm with the NHS, so they don't test for much and their normal ranges are very low.
If you can persuade your GP/Endo to test you then great. If not then try a private test which most members here do to feel well. Post your results here when you have them for comments. Most members buy their own supplements.
See link for companies offering private blood tests & discount codes, some offer a blood draw service at an extra cost. thyroiduk.org/help-and-supp...
There is also a new company offering walk in & mail order blood tests in London, Kent, Sussex & Surrey areas. Check to see if there is a blood test company near you. onedaytests.com/products/ul...
Only do private tests on a Monday or Tuesday to avoid postal delays.
T3 doesn't always suppress TSH. It depends on the dose. Liothyronine is about 3x as potent as levothyroxine in suppressing TSH ncbi.nlm.nih.gov/pmc/articl... .TSH suppression depends on the dose. Some people have a subnormal TSH to start with and so it may be suppressed more easily. I also suspect that one dose a day (compared to three) may lower TSH to a greater extent.
It is clearly wrong to state T3 always suppresses TSH although many people who need T3 may need suppressive doses.
Thankyou for your information. Anything will help me be armed when I speak to my endocrinologist.
Ideally you wouldn't let your TSH go low but sometimes it is unavoidable if we are to overcome hypothyroid signs and symptoms. It's the endocrinologists' job to find out why and about time they put in the effort to do so.Do you have TSH, fT3 and fT4 results from before you started taking hormone or when you were on low doses? This would give an idea of pituitary performance.
jim,
I thought to medicate enough T3-only meds, TSH would always be low?
Is the FT4 level important when medicating T3-only?
And also isn’t there an element with t3 only medicating that we actually want our TSH suppressed to stop any t4 causing any pesky issues!
I can't see how a little T4 can cause problems but possibly that remains to be discovered. I think we need to identify the people who find this happens and categorise them with a view to identifying possible reasons.
Beau55,
I think the low TSH is a consequence of medicating T3 and not necessarily to prevent release of T4 (should there be remaining thyroid gland tissue).
T4 is generally only troublesome when an excess is medicated or produced (as in stimulating Ab’s) that is superfluous to normal requirements. But then it’s not a good idea to have an excess of any hormone.
On T3 only I don't think TSH would always be low. It looks like single or possibly twice daily doses of T3 pushes TSH down and it is slow to recover. So, perhaps bolus doses of T3 behave differently to a steady dose during the day. The only study, the one I cited, used three moderate doses per day.There is a fair amount of evidence that TSH stimulates T4 to T3 conversion. I discuss it here ibshypo.com/index.php/subno... . If someone has a TSH that is lower than average (for given fT3, fT4) it will be suppressed much more easily. Also, to achieve normal levels of T3 in tissues that rely on local conversion of T4 higher serum T3 will be needed and of course this will suppress TSH.
If on T3 monotherapy T4 will be very low. There may be actions of T4 we don't know about so it seems reasonable to include a little T4 just in case.
Hello again,I was on levothyroxine in increasing doses for over 18 months and I gradually felt worse, and worse. I stopped taking it in the end, because no-one would help me and I felt so ill, I became suicidal, and ended up in hospital.
Therefore, I am reticent in taking it again.
I think they should always o TSH, fT3 and fT4 initially. For many patients just TSH and symptoms will be enough from then on. It seems daft not to get a baseline as the tests are very cheap, at least for the NHS.I had in mind adding some T4 to T3 therapy. For people with poor T4 to T3 conversion levothyroxine (T4) reduces type 2 deiodinase, conversion of T4 to T3. In these cases, where there is some residual thyroid function levothyroxine monotherapy just makes things worse.
jim,
Yes, it makes good sense that a T3 drip feed approach stands best chance of raising TSH and an approach I followed myself when medicating a synthetic combo.
Bianco believes TSH has no other known essential usefulness except for encouraging production and conversion of thyroid hormones, so do T3-only medicaters require TSH when they don’t need conversion?
I used to think taking TSH out of the HPT equation must have some sort of ongoing repercussions with the balance of other hormones (even outside the immediate cascade) but I can’t find any evidence of this.
There is good evidence that TSH stimulates T4 to T3 conversion, specifically type 2 deiodinase. This is important because the brain gets 80% of its T3 by using D2 to convert T4. This allows the brain to have different T3 levels to the blood. Thus, if D2 is not working properly restoring blood T3 levels will not be enough for the brain. It drives me nuts that endocrinologists including Bianco can't figure this out.I and other patients need higher than average serum fT3 to achieve reasonable cognitive function. It is likely that this is too much hormone for other organs such as the heart. So trying to keep a normal TSH is important but not always possible.
Ah, thank you Jim,
So do you know how someone medicating T3-only meds achieves the right levels of T3 in the brain if they don't have the D2 conversion to control levels?
A formal study is needed. I think brain response to T3 could be measured by sleep EEG monitoring as I find I get good refreshing sleep with vivid dreams when I'm on the 'correct' dose of LT3.
I find I need around 45 mcg LT3 to sleep well and have a functioning brain the next day. This gives an fT3 around 9.0 which is well above average. This is undesirable but there is no alternative. This is why I encourage people to try to avoid having a suppressed TSH because if it is suppressed for a long time it often never recovers.
We need some decent research and doctors with enough scientific skills to work out what is going on.
I am deffo someone who has a lower than average TSH. On levo only, my T4 was well above range, my T3 was bottom and quite often under range and my TSH was always suppressed. I am now on combo therapy. My Levo was dropped from 138 a day to 75, and 20 T3 was added
Like others here, I prefer to take my T3 all in one go in morning. Reasons being, it’s difficult to split the pill, a pill cutter just disintegrates the pill, and I often forgot the second dose. I am like Hidden , that I have been testing my thyroid levels for years so find it odd to split and have an average T3 rather than a low T3 reading!
On my new dose and testing routine, my TSH is now as low as it can possibly be but still before my endo would panic. But funny enough, my T4 is now below range and my T3 is only slightly higher than before. I probably need a slightly higher dose as I still have hairloss, but I feel 100 times better and have my life back.
So a couple of times I tried the suggested testing protocol where I split the T3 dose. Both times my TSH was suppressed, my T4 very low and my T3 in the upper quarter. This prompted the conversations about reducing the dose, so I have reverted to all in the morning again. The downside of this is I am very tired in evenings, to which my endo suggested to split the T3 and rewrote the prescription of 20mcg of T3 to 2x10 mcg. But of course, the pharmacy continues to order 20, so I remain taking it all in the morning!
Hello, no , gp on NHS only do TSH, sadly.
I agree and use my own test results as evidence. Last test TSH was 4.24 (usual range) and my T3 is at the top of the range but not over, and FT4 is low. I take 35-40 mcg per day and currently splitting doses 3x per day with 25 mcg take at night. I have also tried taking it all in one dose and I don't really feel the difference.
Hypo signs and symptoms are minimal. Best I've felt in my entire life, having been hypo (undiagnosed) since childhood with my mother and all five sibling with hypothyroidism.
See first reply to this post for some papers discussing how T3 lowers TSH relatively more than T4 does : healthunlocked.com/thyroidu....
Not what you're looking for?
You may also like...
TSH levels blood test only
this helps with aches & pains and energy levels. I must admit reading some of the blogs on here...
Skewing Blood Test Results FT3 and TSH.
suppressed TSH. Sooooo, does anyone know how long I would have to be off T3 to get a TSH that is...
Blood testing when on T3 only
recently wrote on here about whether to have a private blood test when on T3 only, and I know some...
TSH only blood test
tests including TSH and T4 as they don’t generally test for T3. To my surprise only the TSH test...
Timing of blood test when on T3 only
take my T3 in two doses - first thing in the morning
and then about 2.30pm. Could anyone tell me...
Blood test result from Tuesday. Result called be skewed
when to take thyroxine for 11am blood test?
timing blood test when taking levo @ bedtime
When (if?) to take levo before blood tests please?
Latest blood tests - is my TSH now at a “good” enough level to be satisfied? 
