I've been reading helvella 's comments on dosing in his dropbox and there is something I don't understand. Could someone please explain how the impact of a small dose on TSH might reduce endogenous production? Wouldn't this only happen if the small dose was sufficient to totally supress TSH (in which case a dose increase not needed). If the T4 dose is insufficient then wouldn't the pituitary still send out TSH and any endogenous capacity to produce T4/T3 would continue?
My question is how does a low dose suppress endogenous production?
Thanks.
This is the quote:
'At the other end of the scale, prescribing 25 or 50 micrograms and leaving for six to eight weeks seems similarly poor practice. As soon as a hypothyroid person starts to receive that dose of levothyroxine, their bodies will start to re-adjust. But with such small doses, the entire dose is likely to be used up within hours, and the impact on TSH might actually reduce what little thyroid hormone they themselves can produce. Careful, considered titration with very frequent reassessments seems vital for those who have to start on very low doses. As soon as the person needs, they should receive a dose increment.'
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Pearlteapot
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I'll try to explain what I mean. But be warned - the discussion below is simplified to the extreme. It is only meant to illustrate - not be a predictor of what would actually happen.
If we take a TSH reference interval of 0.4 to 4.0.
And a patient with a TSH of 100. (And correspondingly low FT4.)
And, assume that the person will eventually have a non-functioning thyroid and so will need 150 micrograms a day. That equates to 6.25 micrograms an hour.
The problem is that the pituitary has been pumping out more and more TSH, but the thyroid has not responded adequately.
With a small dose of levothyroxine, 25 or 50 for example, that TSH might drop significantly.
The person takes their levothyroxine, let's say at 08:00. That means, on 25 micrograms a day, their bodies would use the dose up in four hours. Or on a dose of 50, they'd use it up in eight hours.
But the only reason the TSH got to 100 is that the thyroid simply couldn't make enough thyroid hormone.
If we now drop that TSH, even a little, it will tend to reduce the output of the thyroid.
If that reduction in thyroid output is more than 25 (or 50) micrograms, then the total of thyroid hormone produced by the thyroid and what is taken by tablet won't rise - it will fall.
Or, a different approach, which is very simple. If the failing thyroid can only produce 100 a day, but the body needs 150, any amount of levothyroxine taken that is less than 50 simply cannot, ever, reach the needed 150 a day.
If the amount of levothyroxine taken has any effect at all in reducing TSH, and that reduces the thyroid's output, then - even when they reach 50 - there will still be a shortfall.
Any dose which reduces the thyroid's output has to be greater than that loss of output in order to be beneficial.
And, a small dose in a body which has been severely deficient can have the effect of letting that body start to react more like it should do. If every morning at 08:00 you take a dose, but you have used it up by 12:00 or 16:00, your body will be flip-flopping between "just about enough to keep going" and "severely hypothyroid" - every day.
If that makes any sense at all, it is a miracle.
The reality, as far as I understand anything, is massively more complicated.
And if all I have done is confuse further, I apologise.
I’m trying to understand this 🧐. Does that mean that as you start to take T4 your thyroid stops working and you eventually ( as you increase the dose) replace all your thyroid output with Levo (and/or T3 ) ?
In some people, that is pretty much what seems to happen.
But not all. I am on 112.5, and have been for quite some time. If my thyroid was not producing any thyroid hormone, that wouldn't be enough. (I am a fairly substantial chap almost six feet tall.) So my thyroid must be making some thyroid hormone.
Nowadays, my TSH is typically low within reference interval.
I really don't think there is sufficient understanding of what happens as we approach adequate thyroid hormone dosing.
We see many people on here who’s TSH does not respond appropriately for how hypothyroid they actually are if you look at Ft4 and Ft3
Increasingly only TSH is tested by GP’s and dosing by TSH will leave thousands upon thousands of patients under medicated
some people find it better to take 2 or 3 smaller doses of levothyroxine spread through the day ….even though “in theory “ levothyroxine is a storage hormone
SlowDragon 'better to take 2 or 3 smaller doses of levothyroxine spread through the day ….even though “in theory “ levothyroxine is a storage hormone'
I don't think the need for multi dosing is about the 'storage' aspect of T4, but about the peak in the blood level following absorption from the gut. Some people seem to be much more sensitive to this than most.
But most medics are of the view that it’s a storage hormone and that we could, in extreme circumstances, even take a full dose once a week (wouldn’t recommend it.)
As lau99 has found, taking full dose for week in one go, while doing this under medical supervision, it’s not a constant dose. Post about this here
Medics frequently seem dumbfounded that many patients find they need to split levothyroxine tablets
It seems more accepted by medics that liquid levothyroxine is often better split into 2 or 3 smaller doses spread through the day
Naturally our thyroid wouldn’t put full day’s output in one go, so it’s not surprising that it might give better, smoother more even result splitting the dose
Obviously it’s more inconvenient and important not to forget to take each dose
If someone is fine and well on a single dose, why bother
But if still struggling, trialing splitting the dose of levothyroxine is worth experimenting with
'Medics frequently seem dumbfounded that many patients find they need to split levothyroxine tablets'
Absolutely. The fact that it has an effect before it gets 'stored' seems to be unfathomable to many medics. As so often, they've been 'trained' to believe it's completely innocuous at this stage.
I understand this perfectly , not having a thyroid now and having addisons disease..I used to work as a herbalist and started eating foods and taking tablets to help my thyroid? ..
But this threw the pituitary gland and it thought my body is getting enough hormones to produce what ever I needed for the day so it stopped working ..
I then became very ill so I had to stop everything I was taking from Holland and Barratt and just carry on taking thyroxine ..
I totally get this. I think it explains what happened to me. In the beginning, I was prescribed 50mcg and left there for over two months. My energy plummeted in this time and I felt a lot worse than before diagnosis. Even moving me to 75mg, on which I stayed for a year, was not much better.
This article is very interesting indeed and draws my full attention ! Helvella, would you mind saying from where you got this info…or is it what you have worked out yourself? It’s hardto get to grips with..though have a vague idea…
It sort of makes sense.but…
Can you explain why..bearing all this in mind and accepting as right…
Why over so many years I struggle with it all …despite trying to raise? I’m in this very pit of being under medicated…feeling pretty awful…
And over the years my tolerance of ANY and ALL types of thyroid treatment has decreased ..and now I’m only on 25..mcg Levo…
About ten years ago I was on 75….it always became not enough so up it went to 100..and within a short time would be too much..
This pattern has simply repeated itself in every and any form….
Went on to NDT…and then last two years back to Levo and with little T3…
But can’t seem to cope with anything much…
I’ve put it down lately to low iron levels so trying to build it up .
But I’m curious..naturally ..about what you’ve posted here…
Am about to embark…very gingerly indeed ..on Metavive. .in the hope…🙃
To add to what helvella has said. TSH also plays a small part in stimulating conversion T4 to T3. If your TSH drops then not only will your T4 output reduce but your conversion can be affected too.
If the T4 dose is insufficient then wouldn't the pituitary still send out TSH and any endogenous capacity to produce T4/T3 would continue?
if the dose was insufficient , then the pituitary will still send out TSH ...yes
But it would send out less TSH than it did before the insufficient dose was added... so the thyroid would be 'asked' to produce less.
I think it's fairly safe to assume that even with '0' TSH .. there is still some sort of 'base rate' of secretion of T4/T3 from the thyroid .. it's a gland after all ,and that's what glands do... however unlike most of the other glands in the body , the thyroid gland also has a clever 'boost' function (TSH).... which makes things very complicated, but also makes it very adaptable and responsive to all sorts of changes in demand.
@helvella thanks so much for taking the time out to explain that to me. Miracle or no, it does make sense to me.
* My experience has been exactly as you describe. The mornings would feel okay but by teatime I felt much worse than I ever had prior to diagnosis and medication. I never previously had such extreme brain fog, swollen ankles, fatigue, dry skin. The way you have described it that was because the Levo had all been used and my thyroid was not producing even the amount that it did before diagnosis because even a partial drop in TSH is enough to stop endogenous production from a damaged thyroid. This makes me feel better about my decision to press my GP to let me go to 100mg instead of enduring another 2-3 weeks on 75mg.
* I hope I will be like you and have thyroid that continues to produce a bit rather than stop completely. I have been holding onto a hope that once the source of my hashimoto auto immune inflammation has been addressed the remaining functional part of the thryoid would be 'saved' from further lymphocyte destruction and I might be able to reduce medication to encourage more endogenous production which might be more effective once the lymphocyte attack had jogged on. Is that a fantasy? It’s what Isabella Wentz did, as I understand her.
That truly is a miracle - not on your behalf, but that I managed to pull some words together that make some sense.
You know, I find it helpful when people ask questions that are somewhat challenging. Wouldn't be the first time a question has had a significant impact on how I understand things.
Sadly, I am very sceptical about those who appear to have recovered from autoimmune thyroid disease/Hashimoto's. In the fullness of time, possibly some will be fine but others might have to go back onto thyroid hormone medicine.
Although most members have an autoimmune issue, I don't think I do. My hypothyroidism is pretty much unexplained.
Hi, SlowDragon interesting, why might a split dose increase the conversion rate?
I've been on 100mg for 3 days now and not having the same afternoon crash. In fact I went for a swim in the ponds today which was very good for the soul and I did not crash afterwards. Here I am at 10.45pm still reading HealthUnlocked! The change from 75mg to 100mg feels, so far, like a good decision. On the other hand I am having more swollen ankles and pins and needles in hands - I never had those symptoms before diagnosis. Definitely retaining a lot more fluid. Hoping the water retention/carpal etc is a result of having been on only 75mg till a few days ago and that those things will start to improve as this higher dose settles in.
Jazzw you make him sound like the Doormouse in a teapot. `You might just as well say,' added the Dormouse, who seemed to be talking in his sleep, `that "I breathe when I sleep" is the same thing as "I sleep when I breathe"!'
Im glad the increase to 100mcg of levo is helping. It does take time for the full efects of the body to be addressed, hence the usual gap of 6-8 weeks before dose adjustments called tiltrations. I doubt the pins needles ankle swelling is a consequence of the dose increase. Far more likely these symptoms occurred because of your thyroid failing and how much you needed to start on a higher dose......there is always a time lag. Levothyroxine (T4) is the storage form of thyroid hormones. The body converts T4 into the useable form of T3. The effects of treatment take several weeks to fully impact on the body.You might find it helpful to read Dr Peatfields book called Living with your Thyroid.
Most likely thr pins and needles are caused by the swelling you describe impinging on the nerves. The swelling will go as your treatment takes more effect. It should be reviewed in 6-8 weeks to see if you need a further increase. Your GP will test the TSH (thyroid stimulating horomone) but really you need the thyroid hormones level assessing too (Ft4 & Ft3). You may have to get these tests done privately unfortuante as the NHS increasingly does not test the actual thyroid hormone level, relying just on the TSH.
The pins and needles could also be a sign of low B12. This is commonly low in hypothyroidism so just to be sure I would ask your GP to do a blood test for B12. Folate, ferritin and vit D. Getting these optimal will help in your recovery.
waveylines thanks I will get the book. I agree that the swelling etc is probably due to having been under medicated till now (in the way that helvella describes). Hopefully it will begin to improve now that I’ve gone upto 100mg. This time I will allow the dose proper time to settle but so far I have no regrets at all at having gone up from 75mg after only two weeks. I felt like my brain was liquifying. It was horrendous. Couldn’t think, couldn’t work. Thanks all.
Oooh poor you. Oh no am not suggesting you shouldnt have increased at all. Clearly it had been started at too low a dose for you. Doctors are advised to start the initial dose by weight of the person too rather than just starting at the bottom dose which so many do. So for you it sounds like a good call! Hope you feel better soon. X
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