An hypothesis about RT3 – did you know you might have a hidden pool of it?

Everyone makes Reverse T3 (RT3)–an inactive thyroid hormone. It’s a way to clear out excess T4 when your body isn’t needing that extra storage hormone. i.e. instead of the T4 converting to the active T3, your body (and specifically your liver), will convert it to RT3. If someone without a thyroid problem gets the flu, up goes the RT3 to conserve energy. If someone has a bodily injury, up goes the RT3 to conserve energy.

And thyroid patients seem to see their RT3 go up in the presence of low iron or a cortisol issue.

But if you think about it, why doesn’t it go down faster when we decrease our T4? T4 has a half life of one week, yet it can take 8 – 14 weeks for RT3 to go down....

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19 Replies

  • CC, I think the theory is that rT3 blocks the T3 receptor cells and it isn't reducing T4 that clears excess rT3, it's stopping it for 8-14 weeks.

    I don't know whether rT3 and build up of T4 are the same thing as I didn't test for rT3. I do know that 8 weeks off T4 and trying varying doses of T3 did nothing and it wasn't until I'd been off T4 10 weeks and T3 2 weeks that my 'T4 poisoning' symptoms abated. After 4 weeks off meds I resumed T4 and symptoms started within hours. I doubt I had any rT3 at that point. Adding T3 calmed the adverse symptoms and I'm fine on T4+T3 now.

  • Thank you Clutter, could you list some of the T4 poisoning symptoms?

  • CC, T4 poisoning is my term, not a medical diagnosis. Symptoms were: constant palpitations including at rest, racing and pounding heart, severe internal tremors, parasthesia, tingling and numbness in hands, fibro pain preventing me lifting my arms to comb my hair and wash my back, breathlessness (COPD later ruled out), inability to stand for more than a few minutes before greying out and having to sit with my head between my knees for 10 minutes to recover, suicidal depression, anxiety, despair, weight loss, loss of appetite, severe carpal tunnel pain in left arm/hand, cold to the core, body hairloss, thickened dry skin, head hair shedding, nausea, vomiting, diarrhoea several times daily (coeliac ruled out).

    It was amazing how quickly they dissipated in the 2 weeks off meds. I could raise my arms, walk down stairs without holding onto the bannister rail with both hands and best of all breath easier without the racing heart and palpitations.

  • Hi Clutter, thank you for taking the time to list them. I don't think I have RT3 in that case. Am anxious, depressed but always have been.

  • CC, that's the problem, some things preceded thyroidectomy but were improving on T3 and then got worse again on T4 plus a whole shed load more of problems. My problems may have had nothing at all to do with rT3 and simply been adverse reactions to T4 which are now calmed by the T3 I also take.

    I did ask endo about rT3 testing but he said it wasn't available on the NHS which isn't entirely true as one or two members have had NHS rT3 and I think Southampton has been trialling it. Mind you my endo totally dismissed any chance that T4 was causing my symptoms but I proved it was, to my own satisfaction, anyway.

  • Thank you. I'm sure you've already read the following, shaws posted on another thread, how T4/T3 is assimilated:

  • CC, yes, Dr.Lowe had great understanding because he was himself hypothyroid and his death is a sad loss.

  • I will second that, he was great, can you imagine having him as your Endo? He has left a legacy, but even he himself was shunned. They do not like it when you do not conform with their gold standard TSH test, it panicks them......

  • Thanks cc120 for link to dr Lowe - is there a way to access more of his articles directly from web?

  • I don't know Jacs (anyone?) but I do believe they use his teachings in articles on .

  • Thanks for taking the time to send me all these links clutter - I look forward to reading them. I find his articles interesting to read and hugely informative. I was tempted to buy his book but see it's around £150 (although I'm sure it would be worth it)

    Thanks again

  • Jacs, check whether it is available via TUK's library.

  • I have asked for the rT3 test at least twice with two separate Endos and the same reply, we don't do it. Is that because they don't even know what it is. I have often wondered about the RT3.

  • Marmaris, If they say "we don't do it" I imagine they do know what it is otherwise they'd say they hadn't heard of it.

  • Yes I agree, just like the labs always try to get out of doing the T3 test, they know it is important, but always avoid it.

  • My rt3 went down rapidly, according to labs, when i would lower my t4 meds.. it would go down every 4 weeks.

  • Thanks for posting, cc120. Some very insightful information to help with the piecing together of the jigsaw, and even through the various links onto other websites, and the blog entries.

    I think it's helpful to understand that during illness (no matter how minor or major) there has to be a mechanism to reduce metabolism and rT3 seems to be the key to this. Whether there's a pool of it or not, it would need to be available, even in an ad-hoc way, to slow the body down at a time when energy stores need to be preserved. Injury and illness put a lot of strain on our adrenals, so our bodies need to slow down in order to provide a sustainable amount of energy and resource for recovery. If T3 isn't produced through conversion, after a while metabolism has slowed or stopped and our bodies start to lose all sorts of reserves for sustainability, resulting in the well-known symptoms.

    There's a great deal of information out there by some very generous people who genuinely want to help people with thyroid problems. As there is also on this forum.

    Kind regards


  • Yes, is a very helpful forum.

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