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Thyroid UK
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If FT3 is high in range, FT4 is low but RT3 is slightly elevated & I've still got hypo symptoms, should I reduce T4?

Hi everyone, I would appreciate any help or advice in regards to dosing.

I've read that elevated RT3 can cause hypo symptoms & I'm wondering whether this is the reason I have lingering hypo symptoms despite feeling better since adding T3 to T4. My current dose is 50mcg T4 & 50mcg T3 (25mcg taken in the morning & 25mcg in the afternoon).

My results are as follows:

TSH - 0.29 (0.3 - 5.0)

FT3 - 3.21 (1.5 - 4.0)

FT4 - 0.55 (0.8 - 2.0)

RT3 - 35.2 (25.0 - 35.0)

I feel hypo symptoms slowly getting worse so I know my doses need adjusting but I'm not sure what to do. My iron, B12, Vit D3 levels are all within range. I've read several times that when RT3 is elevated, T4 needs to be reduced but my T4 is already low so which way should I go? Any help is greatly appreciated...thanks : )

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I very much doubt that FT4 is causing high rT3. Is it possibly you have, or have had, some sort of bug or virus? If so, it could be the bug causing your increase in symptoms, because rT3 doesn't cause symptoms.


Thanks for your reply. No I haven't had an illness that may have caused it. Do u think its the low FT4 that's causing hypo symptoms? Should I increase the T4 dose from 50 mcg to 75 mcg? I'm just worried it will also increase RT3...


It doesn't matter if it increases the rT3. What do you think it's going to do to you? No, I don't think the low FT4 is directly causing the hypo symptoms, except in as much as it's not enough to convert to a good level of FT3. Your FT3 could be higher, and that will be what is causing the symptoms. T4 is a storage hormone. :)


Thanks so much greygoose. Sounds logical but there's so much conflicting information out there! I've read that you should reduce T4 to lower RT3 as elevated RT3 can cause hypo symptoms. I've also read that when on T4/T3 combo you should aim for T4 to be mid range & T3 in upper range.

So I'm not sure which way to go to to relieve my symptoms!! I understand that we're all different & that we have to experiment with our doses but I'm not sure whether to increase T3 or T4. I know for sure that I've felt better since introducing T3 & I don't mind pushing it up a bit more so it's higher in range but I'm worried about the low FT4 & the high RT3...any advice? : )


There's so much conflicting information, because research is always finding out new things, and not all the information is up to date.

Yes, normally, to reduce rT3, you lower your T4, but yours isn't high. It's not the amount of T4 you're taking that is causing your rT3. And, if you lower your T4, your FT3 will go down, too. That's not really what you want. Besides, your rT3 isn't that much over-range.

When taking T4+T3, it doesn't matter where the FT4 is, it's where your body wants it to be. I wouldn't mess with it, myself.

My advice is forget the rT3, it's a red herring. If you're sure that everything else is in place : optimal nutrients, etc. - then increase the T3. That should get rid of your symptoms.

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Thanks soooo much : )


You're welcome. :)


Your Free T3 isn't particularly high in range. It's 68% of the way through the range. Personally, I wouldn't call it high in range until it was 85% or 90% of the way through the range. :)

With reference to reverse T3, you might find this link helpful :


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Good article on RT3 humanbean-very clear.

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'since this hormone in excess will bind to your thyroid receptors and start to prevent T3 from getting to your cells'

Except that they've now decided it doesn't block the T3 receptors.

'your Free T3 is extremely low–the result of excess RT3 blocking the cell receptors from getting T3. Very common.'

Surely if the rT3 was blocking the cell receptors so that the FT3 couldn't get in, the FT3 would be high in the blood, not low. This defies logic.

'having pooling aka a high Free T3 due to adrenal or iron problems. i.e. the high free T3 doesn’t cause rising RT3, but both can eventually happen in tandem for many.'

Ahhhhhh... The famous 'pooling'. High T3 doesn't cause high rT3 anyway. Physically, it can't. And, it would be a bit strange to have both high FT3 and high rT3 all from the same amount of T4. Wouldn't it? Doesn't that defy some law of physics about matter cannot be destroyed, or something? I'm no physicist but that doesn't ring true for me.

So, there I stopped reading. I'm afraid this article hasn't improved my opinion of STTM.


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