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Thyroid UK
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Differences - synthetic T3 vs. natural hormone?

Hi all. I've as some may know been trialling differing regimes including a higher proportion of T3 in an effort to improve a persistent lack of energy which has been affecting my work. Also in the hope of improving a tendency to high blood pressure, and getting off the stack of medication (4 types) it requires to control it.

I had about 15 years of quite severe but undignosed hypothyroidism caused by problems in converting and using the hormone i was producing, with attendant auto immune issues.

Starting T3 after a thyroidectomy in 2005 transformed my situation for the better, but no matter what I do there seems to be some shortfall of get up and go.

Increasing the proportion of T3 has definitely helped, but i seem to do better if i maintain no less than 100mcg of T4 in the mix. (it overcomes a tendency to get very tired in the evening)

There's a persistent tendency to low vitamin D for which i've recently started another round of this time much heavier supplementation. The endo mentioned nothing else as being out of whack following the last visit, but I've not seen the results.

I've often wondered about natural hormone, and am wondering if it's worth a trial. On two grounds:

1. Synthetic T3 is almost but not quite chemically identical to the natural variety.

2. Natural hormone contains some additional sub hormone of to my knowledge unknown function.

One issue is that I don't believe natural hormone is available on our local public health system, but it would still be worth it if it did the business.

I'd appreciate your thoughts.

Thank you


11 Replies

So far as I am aware, both synthetic T4 and T3 are the sodium salts of the thyroid hormones. However, I have understood (but am willing to be shown wrong) that by the time it is in your bloodstream, it has had the sodium atom replaced by hydrogen.

Nonetheless, once whizzing round your system, I do not think you can in any way identify one molecule of T3 or T4 as having come from synthetic, desiccated thyroid, or even our own thyroid.

There is also the possibility that the hydration level has its own set of effects? Or that it is mixed up with and, possibly, bound to proteins from the thyroid?

But what else about desiccated thyroid makes a difference to people? We have seen numerous claims of T2 and T1 - I am not convinced as I think there might be a simple misunderstanding going on. Calcitonin has been suggested but recent discussion here suggests that it is likely to be destroyed before it could be absorbed. Certainly there is some significant difference which seems to help quite a lot of people.



ian, Rod's comments are accurate and thoughtful, as they always are. We do not really understand the biochemistry of why some people seem to do much better on NDT and I would be willing to bet it could be different reasons for different bodies. My sister was doing just fine on NDT when the UK banned it around 1978. Synthetic T4 turned her world upside down. When they moved to Scotland around 1982 she finally got a referral to see an endo. He spent three years trying syn T4 and syn T3 alone and in every possible combination to no avail. This is unusual because quite often T3 ends up being what works for many people who are having a difficult time with T4 or NDT. He finally gave up and said, "You just don't seem to get along with this stuff" and wrote her a script for Armour. He did not really have any idea why her body reacted the way it did. Almost thirty years later and we still don't really understand much about why people can react so differently to the various thyroid medications. I've read many of your previous blogs and as I remember you have covered the adrenals already. It always seems to come down to the fact that people have to find out what works in their own body through experimenting and observing the results. For some this turns out to be fairly simple, for others much more complicated. Don't give up. PR


Ta PR, Rod. Ditto on reading your own, Rod's and others' posts - you're way ahead on the biochemistry and the science.

I should have mentioned too that natural hormone clearly makes a world of a difference for some like your sister.

One of the very clear perspectives that have become clear to lately is just how personal an optimised replacement regime is likely to be. It makes a total joke of the one size fits all protocols beloved of the system, and that so many professionals treat as dogma.

:) Sounds (as is often the best move - the body is the most honest arbiter of these things i've found) like it's a case of see if it's possible to dig out a supply of natural hormone and give it a try.

I'm actually doing pretty well on synthetic hormone - my situation is pretty good these days. It's just that having got fairly close to normality (and had flashes of what may be it) it's hard not to reach out to try to take that last step.



ian, I'll mention one unexplained curiosity we came across. We sis got the script she called me for help in tracking down a source of NDT. After some research I called the plant manager for Rohr's manufacturing facility in Puerto Rico where Armour was being made at the time. It was not the first call he had gotten since the UK banned NDT. All he needed was a script and some money and he would ship it to sis direct. This was the first time that sis had ever gotten Armour direct from the factory and when she tried the first batch, WWHHHEEE,

something in there really agreed with her system. Whatever it was seemed to slowly fade over the next 6 months or so. At that time given the shipping and so forth sis was ordering a years worth at a time. We jokingly labeled whatever it was as 'Factor X'. A year later when she got the next batch from the factory, she got the same effect again, and again it seemed to fade after six months or so. She did not think it was the T4 or T3 that was diminishing but something else. This happened every year for the 4 or 5 years she was able to get it direct.

I should mention that sis has a Masters degree with a minor in chemistry and did a chemistry experiment for her masters thesis. She was the proverbial chemistry lab rat. So her observations were not without some chemistry background and training. We, of course, have no idea what 'Factor X' could have been other than it may be something they just haven't figured out yet. When Rohr got sold the situation changed and we had to go back to the regular supply channels. She did not get the effect when she purchased Armour from the regular supply channel. We just chalked it up to one of those little mysteries in life that we will probably never have an answer to, but it was and still is a curious thing. PR


Interesting story PR. This might relate to something similar.

Having had a thyroidectomy that left me totally dependent on not just a supply of hormone but the supply of so far synthetic T3 i need to function - and seen the vagaries of the supply chain and the lack of concern with which pharmacies trot out the 'oh we won't have any for weeks' line (doctors, public bodies and the like meanwhile like to say that it's something to talk to your pharmacy about) - i've a tendency to try to build up a little reserve stock of hormone every chance i get.

That's fine, but about three years ago after years of stability i ended up very hypo indeed. It crept up slowly, which meant that as sometimes happens i didn't figure what was going on until i was buggered.

It took several weeks for me to realise that i had used some (Goldshield) hormone that was perhaps 18 months old. Switching to a fresh batch sorted the problem instantly.

Their product had been rock solid up to that point (notwithstanding a seeming potency issue that started for me in Autumn 2011 and ran intermittently to switching to generics early this year), so i concluded that most likely it was a shelf life issue.

I don't have a reference, and can't remember the details, but i seem to recall that some digging at the time established that hormone (especially T3) has a somewhat variable but potentially pretty short shelf life.

Maybe it was the fresh stuff from the factory that was making the difference to your sister?



ian, yes, the freshness definitely made a difference but we both think it was something else besides the T4 or T3 that was wearing off. Again there was no way to prove anything at the time so it is just conjecture. There is also the problem of when T4 and T3 start declining in potency. I've always ordered my NDT monthly in an attempt to get fresh stock but that is not always guaranteed. Sis also had a TT. I don't have any proof but just from general reading on the forums it seems like NDT quite often seems to work better when you have had a TT. There are always exceptions to every rule in the thyroid world so as we mentioned already, it always comes back to figuring out your own body and what it needs.


On NDT working better after a TT PR. I've a recollection that some on the Thyca group back around 2005 may have held that view - but can't remember properly.

That could point to its containing something that matters - that is less critical while you still have a thyroid because you produce it yourself....



I have the same symptoms as yourself Ian, (thyroidectomy 2003). T3 has has helped a lot of symptoms, but the continuing fatigue is relentless. I am now on 60mcg, of T3, maybe I should be taking more. I have just ordered some Armour, am considering taking 1/2 a gram alongside the T3, and upping to 1 grain to see if it helps fatigue.

If you find the missing link Ian, please let me know, and I will do likewise.


Thanks Margo. It's just so hard to get the last few % to get back to 100%, isn't it? Will do.

As elsewhere i've stepped up to 40mcg of T3 and currently 75mcg of T4 - i've been easing up the T4 without reducing the T3 to see if it might ease the peakiness (feeling fine for a few hours after the T3 kicks in, but fading in a few hours, and evening tiredness) that more T3 seemed to bring.

The extra T3 has improved lots else. Especially gut function, motivation and thinking. I'm actually feeling pretty well provided i don't have to work too hard, but i still find high intensity even light work very tiring. i.e i can handle a day, but feel very tired the next.

The small amount of extra T4 seemed to help, but i'm not sure if it's stable. There's maybe some potential for it to trigger negative responses after a while like production of reverse T3.

Increasing the proportion of T3 even more is next on the agenda, and as you are trialling some natural hormone.

It takes such a lot of time and costs a lot - and money is a bit tight. I'd love to be able to hightail it over to London and spend a load on testing with some of the more holistic services specialising in metabolic illness - by now i don't even trust the (occasional) test results i can persuade out of the system over here because they have been wrong so often.

My vit D has been very low and is currently being boosted with a heavy dose of D3 too. No obvious effects yet though from that. Not sure about ferritin and B12 - will have to chase the endo for those at the next session.

I need to read T3 Paul's book 'Recovering with T3' properly too, there may be a few clues in there...



Glad you mentioned B12 Ian, I don't know how I managed it, as my memory is awful. But for the past year or so I have been having regular B12 injections every month. However, I can't say that I feel any different on it, but it might be the missing link for you. I am sure I read on this forum somewhere, that people with thyroidectomies are often low on B12/Pernicious Aneamia. Just a thought!


Thanks Margo



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