There appears to be so much disagreement about the role of rt3 and its consequences for optimal thyroid health. Is it important to have it tested to get a full picture of what is going on? My Endocrinologist, who has been very good so far, says that to address rt3 issues involves taking high levels of t3 and he believes that would be contraindicated for my Atrial fibrillation. I have heard that this aggressive therapy isn't the only way but it's all academic until I do a test to find out if it's an issue for me. Basically I'm asking is testing for rt3 important and should I pay for it to be done? Has anyone benefitted from having the test? I think it may well be the final piece in the jigsaw puzzle but want to be as sure as possible before I commit. Thank you
Reverse T3 testing?: There appears to be so much... - Thyroid UK
Reverse T3 testing?
marlathome
Basically I'm asking is testing for rt3 important and should I pay for it to be done? Has anyone benefitted from having the test?
High rT3 can be caused by a build up of unconverted thyroxine (T4). Increasing Levothyroxine dose is likely to make it worse.
Usual advice to reduce rT3 is to switch to Liothyronine (T3) only for 3-4 months.
However, there are other causes for high rT3.
Things that can cause high reverse t3 include selenium or zinc deficiency, cortisol issues, stress, dieting, chronic illness, inadequate or low iron, chronic inflammation, high cortisol, or liver issues and any other chronic health issues. and probably several more things.
Conditions that contribute to increased Reverse T3 levels include: Chronic fatigue, Acute illness and injury, Chronic disease, Increased cortisol (stress), Low cortisol (adrenal fatigue), Low iron, Lyme disease, Chronic inflammation. Also selenium deficiency, excess physical, mental and environmental stresses. Also Beta-blocker long-term use such as propranolol, metoprolol, etc. Physical injury is a common cause of increased RT3, also illnesses like the flu. Starvation/severe calorie restriction is known to raise RT3. Diabetes when poorly treated is known to increase RT3. Lyme disease. Cirrhosis of the liver. Fatty liver disease. Any other liver stress Renal Failure. A fever of unknown cause. Detoxing of high heavy metals.
So testing can tell you if your reverse T3 is high but not the reason why.
I can tell you what my experience was.
I tested reverse T3 because I was desperate to get to the bottom of my problem and tested everything I could think of.
At the time, because I already knew I had a conversion problem, I was taking Levo plus T3 and my FT4/FT3 were 62% and 82% through their ranges. My rT3 came back at 22 (10-24), so within range but at the higher end.
I was still tweaking doses of Levo/T3 to find my optimal doses and 6 months later, out of curiosity, I repeated rT3. My FT4/FT3 were 35% and 75% through their ranges and my rT3 came back at 29 (10-24). Obviously it was nothing to do with my thyroid, if it was my FT4 would be high.
Looking at the list of possible causes of rT3 I can pick out some that apply to me.
So I have come to the conclusion that it's not worth spending money on testing rT3 because you'll have no idea what's causing it.
This is just my experience and my opinion, I am not medically qualified and others may have a different opinion.
All an elevated RT3 level tells you is that you have an elevated RT3 level, but not why - it could be the result of taking a beta blocker such as propranolol that reprioritises conversion to RT3 over T3, or another drug that does the same, it could be because you are dieting/restricting calories/malnourished, or because you have a non-thyroidal illness, or are taking too much T4, or taking too much T3, or suffering chronic stress, or, or, or ....... It used to be thought - wrongly - that RT3 blocked T3 cell receptors but now it's known that isn't true. So it's difficult to know how measuring your level might be of practical help, and for myself, I don't see it as a 'final piece in the jigsaw' as discovering that it is high doesn't give you an answer nor tell you what, if anything, needs to be done about it.
I totally agree with both Susie and Maisie. And, I would just add that rT3 is inert, and only stays in the body for a couple of hours before it is converted into T2. So, unlikely to be any sort of a problem.
Thanks greygoose. That's the first time I've heard that about rt3 - I would be so grateful if you would provide a link that explains this in more depth.
I'll see what I can find. But, I think diogenes has posted some stuff on rT3, if you care to look through his posts and responses.
For me, the answer is yes and no. 
No, most of the time. Yes, a year ago when it rounded out the picture. I was very unwell, and my other labs did not really explain it. In fact, they looked better than they had in the recent past and yet I was unwell. I'm not sure that the RT3 explained it either, but it did show that it wasn't all in my mind. Later, when I had my dose adjusted and started to feel better, I couldn't justify testing it again.
For me, in that instance, well worth it. Regularly, not worth it. For me.
For me, I had an inkling that I was not converting T4 to T3, but only when I tested reverse t3 was I fairly sure that was what was happening.
My free t3 and t4 were middle of the range but rt3 high and I was not feeling right. Therefore, I decided not to just take more ndt to get the t3 and t4 higher as likely to keep pushing up the rt3 too but increased the t3 and reduced t4.
Time will tell if it makes a difference and will test the rt3 again to see if changes or not. But probably not test often as the others have said. Rt3 does not tell you why the rt3 is high, but does suggest something is wrong which you can investigate and/ or adjust treatment.
Thanks AKatieD. I know for a fact that I have genetic t4 conversion problems and yet the Endo I am seeing is prescribing NDT and thyroxine. It sounds as though you're proactively addressing your conversion issues - I'd be interested to know how you get on.
Yes, I did the genetic test too. Almost switched to t3 so will try to remember to post when I work out whether it has made a difference.
If your FT4 was only mid-range, then it wasn't the cause of your high rT3. Plus, if you were taking NDT, there is no way to tell how well you convert. You need to be on T4 only to get an idea of that. The rT3 test does not tell you that.
The rT3 only comes from T4? Is that correct?
Thanks, greygoose.
I did the genetic test which suggested conversion issues. Then the blood test, after reducing my meds gradually over time, still showed high rt3 and modest t3 and t4 (around half way through the range) .
I just meant if my t4 was not high through too high dose ndt, then it was not that causing the high rt3 directly. The conversion issue is likely to be correct as otherwise my t3 level would be higher and rt3 lower if the t4 was converting better.
Then rather than increase t4 containing meds, which were likely to increase rt3 further but not necessarily improve t3 levels, it seemed more sensible to increase t3 only to get towards optimal levels. Do you agree?
I just meant if my t4 was not high through too high dose ndt, then it was not that causing the high rt3 directly.
That is true. So, then, you have to look for one of the other causes. Your dose of NDT has nothing to do with it.
The conversion issue is likely to be correct as otherwise my t3 level would be higher and rt3 lower if the t4 was converting better.
But, no, that's just not true. If your rT3 was caused by high cortisol, for example, it wouldn't give you any indication of how well you were converting. There's no connection. And, no, you cannot in any way tell how well you convert on NDT, you just can't, because of the T3 in NDT.
Then rather than increase t4 containing meds, which were likely to increase rt3 further but not necessarily improve t3 levels, it seemed more sensible to increase t3 only to get towards optimal levels. Do you agree?
I do agree that if you can't convert well there no point in increasing T4, but taking NDT doesn't increase your T4 much because of the T3 - that lowers your FT4. But, it all depends how badly you convert, and how much T3 you need. It's really not that simple. First, you have to establish how well you convert by being on T4 only. Then, you have to know how much T3 you need - NDT often doesn't contain enough T3 for some people, so for that reason, it's a good idea to add T3 to the NDT. But, none of that has anything to do with rT3.
Can I throw something else into the mix? What is pooling?
An invention of STTM.
I'm never sure what people mean by 'pooling', because they all seem to mean different things. But, to me, 'pooling' would be T4 or T3 building up in the blood and not being used, for whatever reason. But, due to their respective half-lives, they cannot to that. They both have a limited time in the blood, and are excreted when that time is up. They can't build up into a pool.
So, as far as I'm concerned, 'pooling' just doesn't exist. And, even if it did, why would that be a bad thing? Thyroid hormone in the blood doesn't do anything. It has to get into the cells to have an effect. So, why worry about 'pooling'? If they mean that the hormone isn't getting into the cells, that would be some form of thyroid hormone resistance, so why can't they just say that? It all leaves me a little perplexed.
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