I have been reading two books of Paul Robinson's: The Patient's Thyroid Manual and The Recovering from T3 books
The question I have is something he writes about, which is:
If more levo is taken and TSH reduces, then this process has a knock on effect hindering the T4 to T3 conversion.
Therefore, if Levo is used to suppress TSH, will a patient ever feel well or are patients taking levo doomed to fail because of this physiological process?
Thank you.
People who are hypothyroid who don't take Levo/T4 in any form have no fallback option for their body if they can't get T3 or can't get enough of it. So it is "safer" taking T4 which can be converted to T3 in the body. But since many of us on this forum don't convert very well our best bet in the long term is taking both T4 and T3, or NDT which contains both T4 and T3.
People will stay alive a little longer in an apocalypse if they take T4 and have plenty of it on board, compared to people taking T3 only who could run out within a few days. 
Note, although I don't have any numbers, I am sure that people with very low thyroid hormone levels can stay alive a long time without them. But such people used to end up in mental asylums, so it wouldn't be much of a life.
There is a very old article you might find of interest. It was published in the BMJ in 1949 :
ncbi.nlm.nih.gov/pmc/articl...
I took T3-only for several years because I couldn't tolerate Levo. The problems I had which I am convinced caused my intolerance were low iron and ferritin (iron stores), and high cortisol.
Throughout the time I was improving my iron and cortisol I tried taking T4 every so often but it kept making me feel worse.
Eventually, one of my experiments actually improved how I felt and nowadays I take T4 and T3. I still don't feel great (I have other health problems besides thyroid issues) but I feel better than I did on T3 alone.
It is a bit scary on T3 only as you say, a storage of T4 will be helpful in dire circumstances.
I am going keep mine in a cupboard just in case, with all that is happening in the world, it is scary.
I often think about the current war torn situation and how on earth people are managing / managed without medical supplies.
I too don't seem to tolerate T4, I have tried so hard to try and make it work. It seems that I am a poor converter too. My T3 levels do not budge despite upping my dose, zilch! It hovers at around 3ish.
All I want is bog standard levo, but my body doesn't respond, I feel so frustrated and fed up of feeling poorly.
Thank you for taking the time to reply and I will look at the link that you have sent. 😊
I too am a poor converter of T4 to T3. Robinson''s book contains a way of showing this (you have to be on T4 only, to use this calculation):
Divide your FT3 by your FT4. If the result is over 0.26, you're a good converter, under 0.22 and you're a poor converter. The point is that if you're a poor converter, it doesn't matter how much T4 you take, you'll never have enough, you need to add T3.
Yes this seems to be my experience; the more T4 I have taken (in the hope of more T4 being available to convert,) the worse I have felt; the outcome being that my T3 levels did not improve.😫
Sorry, I'm not clear what you mean by, 'only go[t] the T3 not improve'.
Sorry...just edited my response!
Okay, so now you have the issue of getting T3 and figuring out the ratio of T4 to T3, good luck with that!
So, my latest bloods (May 24) have my T3 @ 4.0 and my T4 @ 20.3, which gives me 0.197, thus I'm a poor converter. Ideally, I should also be taking T3 but I can't get it prescribed by the NHS, I've been trying for 14 years. I could buy it privately but can't figure out what the T4 plus T3 should be. Note that the TSH level is pretty much irrelevant (it's 0.04: range 0.35 - 4.94 mLU/L)
I found the 1949 article for which you gave the link absolutely fascinating. For example, how they diagnosed hypothyroidism and the doses of 'thyroid' (NDT) they gave which were upto 8 grains (8×65mg).
There is a strong possibility that the size of doses and the way they were made is different to the NDT made today.
helvella would probably know if that is the case.
One of the articles referred to 1 grain and said in brackets 65mg. Another referred to 'thyroid'. You're right though, the make-up may have been different.
One grain and 65 milligrams are, effectively, identical. The difference to the 60 milligram equivalence used by some makes is not sufficient to be important except for an individual taking it.
But there is a huge issue in comparing what you see there as "8 grains" and what would nowadays be meant by the same dose.
Thyroid, BP was a different (lower) potency to Thyroid USP. And, the paper having been written in the Middlesex hospital, that paper would have been referring to Thyroid, BP.
While I can be confident that the potency of Thyroid, BP was lower, the different definitions used make direct equivalence impossible to determine - at least historically.
If you scroll down to the History Pages in my blog index, there is lots more detailed information available. Though it can be tough going!
helvella.blogspot.com/p/hel...
And this:
helvella - Desiccated Thyroid - DTE vs NDT vs Glandulars
A discussion about the history of desiccated thyroid and the terms used for it.
Clarifying what is meany by Desiccated Thyroid Extract (DTE), Natural Desiccated Thyroid (NDT) and Glandulars and how the names came about.
Direct link to full document:
dropbox.com/scl/fi/ypun0yes...
Last updated 02/08/2024
Link to blog:
Afraid that link doesn't work!
Try this:
Myxoedematous madness.
ASHER R
British Medical Journal, 01 Sep 1949, 2(4627):555-562
This link should be static:
doi.org/10.1136/bmj.2.4627.555
This link finds the paper in EUROPEPMC and lets you download it:
europepmc.org/article/MED/1...
That's odd. I just went to the link I posted and it works for me.
Oh well - a mystery.
Working for me too - now!
I've had intermittent problems with various US sites which show scientific papers and articles, with my searches claiming that links that I know exist, actually don't.
I've found one way of getting access back again (until next time). I have to flush my DNS. I first started having occasional problems a year or two ago.
The aim of taking T4 - or any other form of thyroid hormone replacement - is not primarily to reduce TSH, that is irrelevant, but to increase FT4, and thereby FT3. And in some people, that can be done without reducing the TSH too far.
Some people manage to convert T4 to T3 without much in the way of TSH. And many, many people do well on T4 monotherapy.
Some people taking T3 feel better when they have high-ish levels of FT4. Others feel better when there's none at all.
So, I think the answer to your question, as for many other hypo-related questions, is: depends on the person.
Thanks Greygoose. I wish I was one of those that do well on levo.
My friend does really well on it and is so active, she reports no problems at all....I wish!! 😊
My understanding of reading Paul Robinson's books is that he says that as TSH falls, T4 to T3 conversion decreases. He doesn't say T4 to T3 conversation stops. It is also well documented that as TSH rises, T4 to T3 conversion increases on an effort to defend T3 levels.My experience proves that as you increase T4, you get less T3 out of each mcg of T4, but given enough T4 you can get T3 at a decent level. However to get my T3 to this level, my T4 level had to be dangerously high.
I agree.
And the critical extra bit - we are all different. While one person might manage to convert T4 into sufficient T3 without T4 reaching the stratosphere, another might not.
yes , BB001
a) we are all individual ,
and
b) conversion abilities within an individual can change significantly over time, eg. see changes in my results over several yrs here : healthunlocked.com/thyroidu...
top of range/ over range fT4 , used to give me fT3 40-60% , and TSH 0.05ish
recently that has deteriorated to fT4 91% (through range) giving fT3 of only 13% with TSH up at 5.3 , despite top end fT4 .
I managed to get my FT3 to 5.2 last year, but my FT4 was 21.4, nearly top of the range 12-22, and I was taking 200mcgs of Levo. I wasnt comfortable with those numbers so I self sourced T3 and added it to a lowered dose of Levo.
I can understand you self sourcing T3 in those circumstances.
Test Results - Is my Levo working ?
Have I come to the end of the road with Levo, feel awful no improvement despite increase.
GP stopping levo, starting T3 at same time... help please!
TSH at 0.02 is this too low?
Is this a silly question about taking Levo ?? 
