High rt3 and adding t4: If you had high rt... - Thyroid UK

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High rt3 and adding t4


If you had high rt3 levels wouldnt you make problems worse by taking more t4. You would create more rt3 that would block t3 from getting to the receptors, right? I haven't had rt3 tested but I felt great starting out on 25 mcg of levo but then I got worse and going up to 50 mcg didnt help. Then I got my blood test and of course my free t4 levels were normal and if that's normal than your tsh will be normal, right? Or does your tsh respond to t3 in the blood? Just trying to learn more about this process.

31 Replies

RT3 is a red herring. It doesn't stop t3 getting to the receptors. That was old thinking. TSH does respond to FT3 levels in the blood.

It is quite usual to get a surge of well being at the start and then hit a brick wall. 50mcg is a starter dose. If you post your results here with the ranges then we can try to help.

Once you are on levo you will usually be best when your tsh is 1 or lower.

I put my lab results in my profile. So can high rt3 cause hypothyroid symptoms or is it just an indicator that you cant convert t4 to t3 well, or both?

Rt3 coverts to t2 and plays a different role. It is low or high Ft3 that causes our symptoms. To judge if you have a conversion issue you need to look at tsh, ft4 and Ft3 levels from the same blood draw. However if you are taking armour you cannot judge conversion as armour has t3 in it. Conversion can y be looked at on t4 mono therapy.

But you should feel better taking t3 if you dont convert t4 to t3 well. Or you will probably have to take a very large dose of levothyroxine to make up for the large amount of t4 that is converted into rt3, right?

It is an individual thing. Some people are fine with low ft4 levels. Others need higher levels. It is a case of trial and error. Most people do however need their FT3 well over halfway through the range usually in the top third. Once you are on combination therapy it is a case of tweaking levo and t3 until you reach a dosage of each where you feel well.

Please don't get hung up on rt3 - it is not particularly useful as a measure. You should concentrate on Ft3 levels.

Many here resort to private blood tests because their doctors don't test Ft3.

There is no magic pill. It takes months and maybe years of adjusting medications until you find the right spot. Just because you have started taking t3 does not mean you will feel better right away. It will take time for your body to adjust to the different hormones again particularly if like me they have been lacking for many years. You need to start slowly with low doses of t3.

What have you tried.? Maybe we can help with dose adjustments.


"The take-home message is that the precise meaning and significance of rT3 are still being teased out. At the current time, there are no standardized guidelines with respect to interpretation or treatment planning based on rT3 alone. Rest assured, however, that TSH, T4, free T4, T3, and free T3 levels are adequate indicators of your thyroid disease severity and management."

There's no such thing as 'normal'. It just means 'in-range'. But, 'in-range' isn't the same as 'optimal'.

It would be very surprising if you were 'optimal' on 50 mcg levo. That's just a starter dose. 25 mcg is a starter dose for the very old, the very young, or those with heart problems.

And, no, just because your FT4 is in-range, doesn't automatically mean that your TSH will be. And, once you're on thyroid hormone replacement (levo) the TSH doesn't mean very much, anyway. It's a very bad indicator of thyroid status because there's no direct connection between the the levels of the Frees and the TSH level.

In any case, wherever the TSH is, it doesn't make you feel anything. Symptoms are caused by T3 being too high or too low. On just 50 mcg levo, your FT3 is probably pretty low, which is why you don't feel well.

The most important thing is ft3 and my doctor doesnt even test for it. What are they teaching these fellas?

Not a lot. Not about thyroid, anyway. It's a growing universal trend to not test FT3 - goodness! If they all tested FT3 and knew what to do about it when it was low, we might all get well, and that would never do! Big Pharma would go bankrupt!

Can too much t4 in the blood cause hyper symptoms? Or is that only when t3 is too high?

It might possibly cause some symptoms, but not necessarily hyper symptoms. But, it would probably have to be pretty high.

Yes slushy47 for me it did. And the definition of ‘too high’ is subjective. Mine never went out of range but was almost at the top of range and yet my FT3 was still extremely low. I did experience hyper like symptoms, anxiety, unable to sleep/switch off. So for me upping my Levo was never going to work. I’m a poor convertor.

Thank you. So I assume you started taking t3?

And you probably stopped taking t4.

My T4 was lowered and I added T3. Then my T4 was too low and so I raised my T4 again. I actually have a high T4:T3 ratio. 7.8:1 but it works for me.

Makes sense. Hope you're feeling good now. I'm kind of a strange case I guess. I deal with high anxiety and depression when I'm not taking anything. Gluten or dairy makes symptoms much worse. I was not on anything when they found out I was hypo. I was having bad anxiety and depression at the time. I started taking levothyroxine 25mcg and my symptoms initially dramatically decreased but came back in like a week. That was like the best week by farI've had since I came off of zoloft like 6 months ago. It seems logical for me to think that most of my symptoms are coming from the thyroid but maybe that is wishful thinking. Maybe my body needs more t3. I'm not sure my doctor never tested for t3 but hes going to test it next time. I've heard of some patients with major depression getting much better on t3. I'm on armour now and I seem to be doing okay but not much difference from when I was on 50 mcg of levothyroxine.

Sorry if that's kind of off subject. I'm just stressed out trying to make decisions about all this.

Mine was a really long reply 😬 sorry 😐

Listen lovely and listen well! You are not crazy to think EVERYTHING is thyroid related. In my view EVERYTHING is. My doctors made me think it was all in my head, they wanted to put so many labels on me. They were even suggesting bi polar, fibromyalgia, then as I moved into my 40’s they were taking menopause, I’ve had MRI’s and heart scans 😩 sheesh the list!

I basically had the lowest opinion of myself, I was tired all the time and couldn’t be bothered with anyone, I had anger issues, I was moody, sad, tearful. I would get an increase in Levo and feel good for 6mths and then the cycle would start again. So so many symptoms that i didn’t Even recognise were Hypo. When I found thyroiduk and saw the list of symptoms, I ticked every box and thought shit! Why am I so Hypo when my results are in range? I was ‘lucky’ that I’ve always been allowed to have my FT3 tested, its just that my GP didn’t know how to interpret the results and just relied on TSH.

Luckily the members on the forum educated me, I spent 3mths reading Hypo everyday.

T3 was my saver and now I know I’m not a lazy, moody, angry person, I was unwell for 12yrs, but probably since childhood. I’m genuinely a happy, bubbly person. Now I think I’m annoying because I enjoy life.

Don’t dismiss your symptoms. It’s quite common for a small increase to my make you feel good and then you feel like you’ve gone backwards but it’s just that your not on a high enough dose yet. Get all your ducks in a row. Private blood tests are the quickest way forward. Make sure T4 is high enough, check it in relation to T3, to see how your conversion is. You’ll need to build up a history of full tests, every time you increase your Levo get a test, this could go on for 6mths before you’d get a full picture. Also Vits and mineral levels are very important.

When you’ve tried all that then and only then is it time to talk about T3.

I hope I’ve haven’t just taught you how to suck eggs 😬 when strangers talk on the net it’s impossible to know where any individual is at with their understanding of their condition/health. I need to learn more about Vits and minerals, that’s my next goal on this journey.

Thank you for your insight. It's very honorable for you to hang around here and help people out even though youre well. If I started feeling well again I'd probably want to get away from all this for a while and actually enjoy life for a change. I need to find myself again. Ive lost touch with who I am as I'm just constantly focused on getting healthy. I'm living in a fog right now and its heartbreaking. I tried increasing to 75 mcg of levothyroxine and my heart started beating out of rhythm all the time but I may have increased too fast. Now I'm on armour 30 mg. Maybe a small dose of t3 would give me hint that I need more t3. I'm on day 4 since switching from levothyroxine to armour and maybe feel slightly better but I feel a little on edge as well.

The thing about being well is that you have time for everything, I’m still so fascinated by the thyroid and I hate that others are still so unwell. At this time in my life I’ve started a new job, I’m at college, I’m renovating my house, I’m planning my daughters 18th, Im still mum to four teenagers, I just have time for everything 😊

So did you just stop T4 and start armour? Do you know your a poor convertor? Do you know that your vitamins and minerals levels are good?

I'm glad you're happy 🙂. My b12 was low normal last time I checked but I've been supplementing. No I dont know if I'm a poor converter. My doctor didnt test for t3. He wasn't going to raise my levo since my t4 levels were near the upper range so I asked if I could try something different. He is testing for t3 next time though since I convinced him to. So I'm just hoping t3 is the answer and I dont convert well. What is the average dose of t3? I think 30 mg of armour is like 24 mcg of t4 and 6 mcg t3. I feel a little better since I got on armour. I was starting to feel miserable and high anxiety again on 50 mcg of levothyroxine.

cazmania7 in reply to NWA6

Wow. Inspiring. I really hope T3 works for me, too. I’d love to be annoying because I enjoy life lol

dragonfly76 in reply to NWA6

Hi do you just take T3 medication, no T4?

I'm taking armour 30 mg.

dragonfly76 in reply to NWA6

Do you take T 3 only ? Thanks

No I dont take t3 only.

It may take quite awhile to find your right dose. I had to raise mine a tiny bit every 6-8 weeks (each time I hit a wall) for almost a year. You may just need more raises and more time.

Appreciate the help 🙂

It would depend on the reason for the high rT3. If it was purely because FT4 levels were too high, then yes, it wouldn't help. If it was because of chronic disease or low calories, for example, maybe it would help. rT3 does not block t3 from getting to receptors as the receptors are quite different. It USED to be thought that they were the same but modern research has disproved that. T4 is converted into mostly rT3 and some T3 (av 60/40) by everyone, but under certain conditions, the %age conversion to rT3 increases (or decreases). No blocking involved.

Thank you all for posting things like this! I find it all so helpful. I added Synthroid to my NDT earlier this year and my RT3 went from 9 up to 19. I feel really good. So I was puzzled by the RT3 result & have been trying to figure out if it even matters. These posts are awesome!

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