How the body deals with T3

[Puddleperson]

I've searched everywhere but I can't find what I'm looking for. I'm either going completely mad or I'm sure I read an article, some time ago, explaining how the body deals with T3 by using what it needs and converting the rest to more inactive forms before excreting it completely. Is this true? Does anyone have a better filing system than me and can actually retrieve it?

[helvella Administrator Thyroid UK]

I do not have a full picture, but there are several things that can happen to T3.

It can be converted to T2 (two different forms can be produced), or glucoronidated (add a sugar molecule), or sulfated (add a sulfate group).

I don't see the T3 pathways as dealing with an excess of T3 readily. After all, many people really do notice the tiniest change in T3 when they take it. It looks to me to be the standard pathways that it follows.

I suspect you might have been remembering this:

thyroidpatients.ca/2021/08/...

[Puddleperson in reply to helvella]

Thanks, helvella. This isn't the same article but possibly contains much of the information I'm remembering. I'll need to find a quiet time to read it all carefully as it looks pretty complex. The basic premise of the one I think I'm remembering is that T3 isn't the dangerous medicine that the medical profession would have us believe as the body simply converts and harmlessly expels any excess it doesn't need. Maybe it's just me wishful thinking?...

[DippyDame in reply to Puddleperson]

Apologies for asking but are you by any chance confusing T3 with rT3?

On one hand I guess it depends on how much T3 is transported from the serum into the nuclei of the cells where it becomes active.A form of hormone resistance causes this....my problem.

It causes low cellular T3...and health problems.

The "extra" T3 that remains in the serum ( still inactive) will be "broken down" and excreted via bowel and bladder.

Is this perhaps what you have read?

Or this...

Excess T4 on the other hand is converted to rT3 and is eventually excreted.

T3 is a powerful hormone and has to be used with care and understanding,...medics don't always understand this.

When used correctly it is not a " dangerous medicine" but when wrongly used it most certainly is.

Having a high Free T3 because of untreated hyperthyroid or through taking so much thyroid medication that you are overmedicated, resulting in a racing heart, shaking hands etc is what is dangerous.

I need high dose T3-only to function so have travelled this road!

Just a few thoughts.

[helvella Administrator Thyroid UK in reply to DippyDame]

Reading Puddleperson's response with yours, I wonder if it is the binding of T3 in the blood that is being asked about?

A huge proportion of the T3 in blood is bound to a protein. Thyroid binding globulin (and others). That means that very little is available to be taken up by cells.

As Free (unbound) T3 is taken into cells, more T3 is released from being bound. That means the Free T3 level is far more stable than if there were no binding step.

[DippyDame in reply to helvella]

I bow to your much greater knowledge!!Something about PP's question puzzled me. ...

[helvella Administrator Thyroid UK in reply to DippyDame]

Yes - it reads more like how T4 is handled - as in it doing little or nothing until it is converted to T3.

Hopefully Puddleperson has enough here now. And, if not, will let us know what else is needed.

[Puddleperson in reply to helvella]

Thanks all for your replies. I've certainly learned a bit more. My question was never meant to be technical. I'm just always looking for ways to defend myself if I'm ever unfortunate enough to have to consult a GP. Perhaps foolishly I have been honest with them and told them that I take T3. Perhaps especially given that they don't accept there's anything wrong with me (TSH in 2009 was a mere 3.4 and debilitating symptoms meaningless) they, of course, strongly disapprove. I'm told that my heart will give out and bones crumble away to nothing the latter, of course, being nothing to do with any other possible cause - even the omeprazole they happily prescribe. So the article I was searching for told a very different story. The gist being, yes of course you need to be careful if taking T3 but it really isn't the dangerous drug the medical profession portray it to be. It's unquestionably given me a much happier healthier 13 years than I would have had without it so crumbling bones (which I don't have) and failing heart (which I also don't appear to have) I shall continue to take it. Maybe as I have failed to find the original article, or indeed anyone here who can remember it, I'm either imagining it or it was a load of rubbish that's been binned and forgotten!

[helvella Administrator Thyroid UK in reply to Puddleperson]

Well-being is a very strong sign!

[Hidden in reply to helvella]

Do you know if T3 that comes from conversion is bound or unbound?

[helvella Administrator Thyroid UK in reply to Hidden]

As I understand:

When it is formed by conversion, it will initially be unbound (free). If it gets released from the tissue in which it was converted, then it will be subject to the same dynamic equilibrium between bound and unbound as all blood-carried T3.

Some tissue, e.g. hair follicles, appear to convert solely for their own use. Others, such as liver, parts of brain, and thyroid itself, can release T3 back into the bloodstream.

[Hidden in reply to helvella]

Ok, thanks! It is not always easy to understand how it works...!

[jimh111 in reply to helvella]

Thanks for posting this link. It's an amazing piece of work, the amount of effort that has gone into compiling it is enormous. I've done my brain in recently so will just file this document away for a (very) rainy day!

It shows how lazy some doctors are when a hypothyroid patient can do all this research and writing and have a full time high power job.

[helvella Administrator Thyroid UK in reply to jimh111]

That article is what I wanted when I first started reading about thyroid hormones.

Plus the article I posted yesterday, or day before, about exactly what thyroid hormones do. (Would be nice if that one had clear inforgrams as well.)

[jimh111 in reply to helvella]

Yes, I downloaded that paper last month but haven't got around to reading it. I was interested because it refers to the integrin receptor and cancer.

[Yostie in reply to helvella]

Thank you for this.

[helvella Administrator Thyroid UK in reply to Yostie]

It is Tania (the author of that blog) who really deserves the thanks!

[DippyDame in reply to helvella]

Tania comes to the rescue again.That kicks my attempted explanation into the very long grass!!

[humanbean in reply to helvella]

I suspect you might have been remembering this:

thyroidpatients.ca/2021/08/...

According to that article :

T3 (Triiodothyronine): The most active thyroid hormone metabolite, usually more abundant than Reverse T3. It is created from T4 via deiodinase type 1 (D1) and type 2 (D2) enzymes.

Can I just check... The author is talking about Total T3 being more abundant than Reverse T3? Yes or no?

I got my Reverse T3 measured three times back in 2013/2014 before I found out it was a waste of money. In each case my Reverse T3 was orders of magnitude higher than my Free T3. I have never had Total T3 measured.

[helvella Administrator Thyroid UK in reply to humanbean]

I think it is referring to Total T3.

I just grabbed some reference intervals for the three obvious tests.

RT3 10 to 24 ng/dL

Total T3: 75–195 ng/dl

Free T3: 0.2–0.5 ng/dl

RT3 much lower than TT3 but higher than FT3.

I think in my earlier reply, I didn't emphasize that T3 produced within a cell doesn't contribute to TT3 or FT3 until it is exported from the cell.

[humanbean in reply to helvella]

Thank you.