Can someone confirm, if I take only levo, I have no control over my level of T3. I presume my body extracts what it needs from the T4 to convert to T3. So whatever level my T3 is, is the level my body needs????
Levo and natural T3 levels: Can someone confirm... - Thyroid UK
Levo and natural T3 levels
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fiftyone
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fiftyone,
Well in theory, yes but there is a small subset of people whom medicating Levothyroxine mono-therapy will never supply them with enough T3 for wellbeing. This because of a known genetic converting impairment and the only solution is to medicate a little bit of T3 added to the thyroxine.
Because of the way the thyroid enzymes work the presence of even a small amount of T3 will encourage own bodys conversion mechanisms to function better so the amount of T3 we end up with in the blood stream is often slightly more than the amount we medicate.
Having the impairment even with both sides effected doses not necessarily tell us to what degree, as genes are influenced by multi factors so the only answer is to raise T3 slowly until relief of symptoms. Other factors known to inhibit thyroid meds from working must be addressed first to eliminate them as the symptom causations, and a common cause is low iron which reduces the conversion of T4 - T3. Other nutrients commonly deficient are Vit B12, folate & Vit D.
No, not quite.If you take T4 (levo) only you can still have problems with your ft3 level.
Firstly your body has to absorb the levo correctly to give you the optimum level of ft4.
Then you need to have good levels of vitamins and minerals to be able to process the thyroid hormone properly.
Then the body has to efficiently convert your ft4 into ft3. Some folks have a genetic problem which disrupts this conversion and impairs the ft3 level. Some folks just don't convert well and again their ft3 is lower than it should be compared with their ft4 level.
TSH is also a factor in stimulating conversion. A below range TSH on levo only might play a small part in lower ft3 levels.
A normal thyroid produces about 100mcg T4 and 10mcg T3. Some of us with no functioning thyroid find that we need that extra bit of T3 our thyroid would have produced.
How do you know you have poor conversion?
You need to be on an adequate dose of levo - shown by a TSH around 1 and ft4 well in range.
You need to get TSH, ft4 and ft3 tested from the same blood draw.
You expect ft4 and ft3 to be similar percentages through their ranges. Ft3 often lags just slightly behind ft4.
My TSH was 0.19 (below range) ft4 was 60% through its range and ft3 was 16% through its range consistently - these figures allowed me to put forward a case of poor conversion and allowed me to get T3 liothyronine added to my levo dose on the NHS.
would it be right to say that TSH level just shows how much thyroxine is in the blood and nothing more?
fiftyone,
No, the TSH level shows how much TSH is in the blood and for many people can be a very poor measure of thyroxine levels.
but the level of TSH in the blood is related to how much thyroxine there is in the body and nothing more. If not, what exactly is the TSH level related to?
You mean Ft4 shows how much levothyroxine is in the blood
🤔 Yes SD, it certainly does! But O/P’s referring to TSH & Levo. Absolutely no mention of FT4 😁.
no. Does TSH level indicate whether there is ALREADY a high or low level of thyroid hormone in the blood.
TSH is a 'messenger'. It tells the thyroid what level of thyroxine is required. As far as I am aware, TSH level is a reflection of how much thyroxine is swishing around in the system. So a suppressed TSH would in indicate there is loads of thyroxine in the blood stream and a high number would indicate there is perhaps not enough. So the TSH is just a measure of how much thyroxine is in the bloodstream.
It is not just 'thyroxine' (T4) that affects TSH... T3 also has an effect .
Does TSH level indicate whether there is ALREADY a high or low level of thyroid hormone in the blood.
Yes .
BUT due to the complexities already mentioned .... it can't always be used as a reliable indication of whether T4 and T3 are TOO high or TOO low.
that's what I'm trying to clarify. There is no complexity with TSH. It's simply a measure of how much thyroid hormone is in the blood and nothing else. Hence it's the best argument to give doctors for testing T4 abd T3
No not necessarily
Medics tend to assume it does…..
But we see many members on here who have low TSH and low Ft4 and/or low Ft3
Just testing TSH is totally and utterly inadequate when on any thyroid replacement hormones
Always test thyroid levels early morning, ideally by 9am latest and last dose levothyroxine 24 hours before test
When adequately treated Ft4 is likely to be at least 60%-70% through range in order to get high enough Ft3
Some people need Ft4 even higher, or over range to get Ft3 high enough
You will see many test results from Medichecks, Blue Horizon, or Thriva on here where TSH is below range, but Ft4/Ft3 are low
Random selection of results here
Medichecks
healthunlocked.com/search/p...
Blue horizon
healthunlocked.com/search/p...
Thriva
fiftyone,
Although TSH helps us convert the level can not guarantee how well we convert, or whether we convert to T3 or RT3, or if the feed back loop has become skewed through years of remaining undiagnosed with inadequate thyroid hormones.
Surely the TSH level reflects the amount of thyroxine in the body?? Surely it only stimulates thyroxine production if there is insufficient in the body in a healthy individual.
Therein lies the problem - in a healthy individual.Once you have thyroid problems you are no longer that healthy individual. The dynamics of the very fine feedback loop that is the endocrine system has become disrupted.
Once you start ingesting an external source of thyroid hormones, which you need to do if your thyroid is faulty then, you also influence the feedback loop.
The TSH range must also be mentioned here. If the range for TSH is 0.27 to 4.50 then in theory a TSH anywhere in that range would show that a person has enough thyroid hormones in their blood. But this is not the case. For years my TSH was between 4.0 and 4.50. My ft4 was 15 (range 10 to 25) the medics were happy and I was still very symptomatic.
Then I eventually got onto a dose of levo that led to my TSH being 0.19 and my ft4 19 (same ranges) - I was still very symptomatic. This was because my FT3 was just above the bottom of its range. If the doctor had gone by TSH alone she would have decreased my levo dose given that TSH was below range. What I needed was an increase in levo to get a higher ft4 or the addition of T3 - I got the addition of T3
TSH does much more than just stimulate more T4 production when T4 is low.
It has a feed forward function as well as a feedback function.
It is influenced by T3 levels as well as T4 levels.
It influences deiodinase conversion of T4 to T3 / T4 to rT3/ T3 to T2 etc as well as the thyroidal production of T4 AND T3.
Not all TSH has the same strength of effect .. there's more than one 'sort' of TSH. (i think ?)
There's lots of complexities ...and most of them are in the 'not properly understood yet' box .
fiftyone,
Yes, TSH is secreted in response to low thyroid hormone so has an inverse correlation but this can become blunted or influenced by many other factors.
The fact we need to even medicate thyroid hormone replacement signifies huge change/disruption to a normalised thyroid signalling mechanism, which may be further disrupted by problems within the immune system & low nutritional status induced by the hypothyroidism.
This means with reference to medicating thyroxine if TSH is to always be kept within range there risks a chance of thyroid hormone remaining too low, or alternatively should thyroid hormones be raised (through more meds) TSH will fall below range. This is probably the most common problem seen on the forum as doctors continue to dose by TSH.
Factors effecting TSH may include medicating T3, central hypothyroidism (problem with pituitary or hypothalamus), resistance to thyroid hormone, recent/long term non-thyroidal illness, TRAb's even in the presence of Hashi. Even smoking will result in lower TSH levels risking a patient always remaining under-medicated (not that I advocate smoking, but it is just yet an example of the inappropriateness of using a pituitary hormone to assess thyroid hormones levels.
Th only way to get a proper assessment of thyroid hormone levels is to test the thyroid hormones together with TSH.
EDIT - PLEASE NOTE NO MENTION OF CONVERSION HERE fiftyone 🤣
Isn't my question fairly simple? All these thyroid problems you mention are not the FAULT OF TSH surely. Isn't TSH level merely a reflection of hormone levels in the blood stream and nothing else which is why it is so useless. ( How well thyroxine hormone is used and what affects thyroxine levels in the bloodstream is a separate matter). Perhaps I just haven't understood.???
fiftyone,
No, they are not the fault of TSH but reasons why TSH can not be a reliable marker of thyroid hormone levels.
Your post initially refers to 'T3 and TSH' and as TSH is a contributory factor in conversion it has to mentioned by default.
Your questions then progressed to "Surely the TSH level reflects the amount of thyroxine in the body??' No, it doesn't always. For some people TSH hasn't moved in years in spite of alterations to their thyroid hormone levels.
Members have tried answering your questions clearly and we are all basically saying the same thing but nothing about thyroid hormones is simple. 😊
you seem to be asking "is TSH a measure the same as a petrol gauge" measuring high /low level of petrol (T4) in tank (blood)...... but it's just not that simple.
TSH is more like a measure of torque (?) ... effect /force required.
it takes into account how much power your engine has made from that petrol,
and how steep the hill you were driving up was ,
and it's a measure of how much more you will have to put your foot down ,or to ease up ,on the accelerator to keep the car going at the same speed up that hill.
No.
Consider two circumstances:
First, someone is hyperthyroid (maybe they have Graves' disease). TSH drops, and drops, until it is suppressed. (By which I mean, as close to zero as makes no difference.)
When the Graves is treated (e.g. they take Carbimazole), TSH can remain suppressed for weeks, months, even years.
Second, someone is profoundly hypothyroid. TSH rises to the maximum the pituitary can produce. If that is insufficient, the pituitary can even enlarge (hyperplasia) and, eventually, will produce more TSH. Thus, TSH can rise higher than ever it could in a person with no thyroid issues.
When the hypothyroidism is treated (whether levothyroxine, liothyronine, or any combination), TSH will drop. But TSH will not go directly to the level that person would have had before any thyroid disorder. It will quickly drop a bit, but it can take a significant period of time even on sufficient thyroid hormone, for TSH to approach the original level for that person. And, at least while the pituitary is still enlarged, it will continue to be able to produce more TSH than is necessary. In that state, TSH is rather prone to excess swings.
But, in both the cases above, TSH is affected not only by how much thyroid hormone is in the person's blood, but also by the history of thyroid hormone levels over months or years.
In a person without any thyroid disorder, TSH is affected by the level of T3 within the pituitary - but that T3 comes about from two sources: T3 in the blood and T4 converted to T3 within the pituitary. (It is even possible to have a disorder in which T4 is not properly converted to T3 within the pituitary. Pituitary resistance to thyroid hormone.)
Many factors affect conversion of T4 into T3 (and reverse T3 if there is sufficient T3). These too cause the TSH-to-T4-to-T3 mechanism to be upset and not work as it would in a person with no thyroid issues.
Your original question suggests that sufficient T4 would automatically imply sufficient T3. That can be deeply questioned by considering what happens in someone who takes an overdose of T4. And I mean a significant overdose - such as dozens of tablets.
If T3 did not rise above the level needed, why would such an overdose matter?
What happens is that the T4 level rises based on absorption from the tablets taken. At that point, the person can seem pretty much OK. But around two days later, the T3 level can shoot up. That is pretty much the danger point. Is T3 rises too far, they can die.
(The real danger is a doctor who does not recognize the delay and assumes after a few hours that the patient is fine and discharges them.)
Children, especially young children, seem particularly resistant to T4 overdosing. If you think that the ability of a child's body to convert T4 into T3 will be limited, partly due simply to size and speed of metabolism, that means that T3 is likely not to rise as much as in an adult.
Endocrinology seems to take the idea you ask about as if it were true. But they then lose their nerve when someone wants a small increase in their levothyroxine. If that idea were 100% true, we could all be prescribed relatively high doses of levothyroxine and live happily on them.
I notice the difference between 112.5 and 125 micrograms of levothyroxine a day.
My doctor wanted me to reduce from 125 to 100. For me, 125 was too much, and 100 too little.
I can't explain that if I take your original suggestion as true.
thank you. Never realised there could be such lag between thyroid dose and change in TSH.
Nor do an awful lot of medically qualified people.
The extremes would appear often due to the severity of the disorder as well as how long it goes on for.
"Never realised there could be such lag between thyroid dose and change in TSH."
For example , at diagnosis (after being undiagnosed hypo for 4 yrs):
~ my initial TSH was 6.8 (TotalT4 ~ 29%)
~after 7 weeks of 50mcg TSH 2.9 (TotalT4 ~ 52%)
~ after 5 months of 100mcg TSH 2.5 (Total T4 ~ 68%)
~ after 3 months of 150mcg TSH 2.7 (TotalT4 ~ 71%)
but a year later (after only a week or two of 175mcg ?) :
~ TSH 0.001 (FreeT4 ~ 189%)
I reduced back to 150mcg, but the TSH didn't go back to 2.5 ish ....for the next decade, still on 150mcg my TSH stayed between 0.05 and 0.5 regardless of whether my FreeT4 was as low as 50% or as high as 130% .
Over that first year that i was on 50/100/150mcg Levo , (with increasing Levels of TT4 in my blood) ...my TSH didn't see to move much (apart from the initial drop from 6.8)
And then after TSH had gone 'low' , it didn't comeback to where it was before , despite the same levels of thyroid hormone in the blood as before.
(The change from testing my TotalT4 to FreeT4 is unhelpful , but i'm sure you still get the picture, about the time lag /unreliability of TSH as a measure of blood levels of thyroid hormone)
if it was the case that , assuming adequate T4 supply, the body always continued to convert enough T4 to T3 for its needs, no more, no less... then you would expect the ratio of T4 : T3 levels to be very similar in patients on Levo, to the ratio in people who produced their own thyroid hormones.
But that is not what we find .
In patients on Levo, we usually find a relatively lower level of T3 / higher level of T4 / lower level of TSH, then in healthy people who still make their own.
(in a study of 10 healthy people, half of them had T3 levels that were equal to, or higher than T4 levels , but you wont find this in hardly any of the results people regularly post here from using Levo)
If T3 :TSH :T4 levels in Levo takers were always 'what the body needed, no more no less'... then that would sort of imply that many 'healthy' peoples bodies were regulated by their TSH to make rather more T3 than they actually needed. ie healthy people are 'naturally overmedicated with T3' ....... which is obviously a daft idea.
So there must be something else going on here, and it stands to reason that whatever the 'something' is (from multiple, complex possibilities)... it is likely to be part of the explanation for why some people don't get properly better on Levo alone.
I am not talking about conversion etc. All I'm asking is does the TSH level indicate the level of thyroid hormones in the body, not whether everthing is working correctly. Simple answer anyone??? If the TSH level is suppressed, I presume it is indicating there is loads of thyroxine hormone in the body and if it is unduly high, that there are low levels in the body,
simple answer . No . It relates to T3 level too ( not just thyroxine)
People who take T3 only have below range T4 but they still have supressed TSH.
so TSH level is a measure of thyroid hormone (T4 and T3) in the blood stream (not how well they are being converted or used by the body's cells)????
No . TSH level is a measure of THE EFFECT OF of the thyroid hormones T4 and T3 ( in the blood stream) ON the pituitary gland .
But yes you're right , TSH level CAN'T tell you how much thyroid hormone T4 /T3 is in the cells of for example ,your heart muscle ... or your brain cells .
The pituitary cells might have 'enough' , so TSH stays low. But that doesn't always mean the heart, or brain, or skin has enough .
There was a study on thyroidectomised rats which proved (by chopping them up, it's the only way you can tell tissue levels of T3) that not all tissues achieved 'normal/adequate' levels of T3 when just taking Levo .
But their pituitary gland , (that makes TSH) had 'enough' ( it gets 'served first at the table' ) so if you just looked at their TSH , it would indicate 'we've got enough thyroid hormone' ... but the heart (or something else) might not have enough .
yes that's a slightly different way of looking at it. thanks
In a healthy person it does.In a person on replacement hormone therapy it does not.
The study below is scientific but its conclusion is easily understood
"The data reveal disjoints between FT4–TSH feedback and T3 production that persist even when sufficient T4 apparently restores euthyroidism. T4 treatment displays a compensatory adaptation but does not completely re-enact normal euthyroid physiology. "
In the case of thyroid hormone dosage with either T4 only, T3 only or combination, a given level of TSH cannot and does not reliably indicate a given FT4 or FT3 level. It does so in health, because all the factors work together and maintain health at the appropriate level. If you have no thyroid working at all, then this mutual control flies out of the window. This is because a well-working thyroid produces a certain amount of T3 direct, adding to the T4-T3 conversion in the body itself . This ratio of T3 production (thyroid/body) is unique to each person, and the TSH level required to do this is also unique. As the thyroid dies, then the remainder maintains its T3 production, but can only produce less T4 - the body conversion has less T4 to convert. Thus the TSH will rise, mirroring mainly the depleting T4. But the link beween TSH and FT3 is lost. If the thyroid lost altogether, then there is no thyroidal direct T3, so the patient must take in extra T4 to allow the body conversion to make up the difference. This of course will reduce the TSH, which in this case is only a much l ess important passenger rather than the driver it was in health. So the answer is: in health the relationship betwen TSH and thyroid hormones is set for the individual patient, but has a definite relationship but in treatment not.
All I'm asking is does the TSH level indicate the level of thyroid hormones in the body, not whether everything is working correctly.
Simple answer...Yes it does!
High TSH = low hormone level
Low TSH = high hormone level
TSH is a pituitary hormone not a thyroid hormone. It is a signal to the thyroid to produce more, or less, hormone
BUT..., it does not distinguish between T4 and T3
For that FT4 and FT3 need to be measured
Because those are the important readings
Of the two, FT3 is the more important.
Overmedication is unlikely if FT3 remains in range
TSH was originally designed as a test for hypothyroidism not as an aid to dosing.
The waters became muddied once it was used as a short cut for evaluation of thyroid function/dosing
thyroidpatients.ca/2021/07/...
But I guess that's more than you asked for!
thanks. At last. Why doesn't anyone else understand my question?
You're welcome!
I just answered your rephrased question copied to my reply above.
But, the others did understand....just from a different perspective.
Your original question was a bit difficult to understand and you were given good informative answers to that.
if I take only levo, I have no control over my level of T3
The amount of levo you take and the conversion of that T4, to T3, will help determine the level of T3 in your blood. Your only control there is the dose of levo you take!!
Then you asked...
So whatever level my T3 is, is the level my body needs????
I had difficulty with that one....but no!
The level of your FT3 lab reading helps to indicate whether you need to raise or reduce your dose....or do nothing.
The hormone level your body needs is the one that makes you feel well...in healthy people that will be adjusted by the body's feed back loop.
When people are hypothyroiod the body needs help and the correct level is found by taking replacement hormones ...T4 or T4/T3 or T3-only depending on the underlying problem
We are all different so that will vary from person to person
It's all quite complicated. When I arrived here a number of years ago I'd been diagnosed for over 20 years and had never heard of T3. The internet and this forum helped to change that and the learning process began!
The collective knowledge and experience of members here exceeds that of most medics, so ask away....someone here is likely to have faced the problem already!
SlowDragonAdministrator
Just testing TSH and Ft4 is completely inadequate
On levothyroxine we frequently have low Ft3 ……especially if vitamin levels are low
EXTREMELY important to regularly retest vitamin D, folate, ferritin and B12. These need to be OPTIMAL for thyroid hormones to work well
Very common to have low vitamin levels on levothyroxine, due to poor nutrient absorption as result of LOW stomach acid
Bloods should be retested 6-8 weeks after each dose change or brand change in levothyroxine
How much levothyroxine are you currently taking
Do you always get same brand levothyroxine at each prescription
Many people find different brands are not interchangeable
For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested.
Very important to test vitamin D, folate, ferritin and B12 at least once year minimum
What vitamin supplements are you currently taking
Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water and last dose levothyroxine 24 hours before test
This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)
Private tests are available as NHS currently rarely tests Ft3 or all relevant vitamins
List of private testing options
thyroiduk.org/getting-a-dia...
Medichecks Thyroid plus antibodies and vitamins
medichecks.com/products/adv...
Blue Horizon Thyroid Premium Gold includes antibodies, cortisol and vitamins by DIY fingerprick test
bluehorizonbloodtests.co.uk...
Come back with new post once you get results
From my own thyroid dosing with T4 sole regardless high/lower dose after my TT I experienced many side effects. Palpitations ,anxiety, panic attacks, wired /tired,weight issues,high BP,jaundice, moodiness etc. Adding some T3 either with NDT or synthetic T3 made a huge difference. For some of us T4 does not convert T4 to T3 efficiently. The heart has a big receptor sight that needs T3.For T3 to work well and to tolerate one must have nutrients up to par. Especially Iron, vitamin D, B-12/ folate ,minerals.
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