A case for the rt3 ratio?

A case for the rt3 ratio?

I started on ndt in July and have my first lab results.

Please see photo for ranges/details.

fT3 dropped from 2.6 to 2.1 and fT4 dropped from 1.2 to .68

So, you would be thinking how dreadful I must feel now? But I feel great for the first time in a long time!

The ft3/rt3 ratio went from 13 to 24. So, I'm sold on the ratio being a big part of the equation. I know that there is disagreement about this, but this is my experience.

Oh, and endo is upping my dose to 2.5 grains...

25 Replies


It's common for FT4 to be lower when T3 dose is increased but FT3 dropping indicates undermedication. I'm surprised you feel so well with lower FT3.


You are surprised because you don't believe that the ft3/rt3 ratio can cause hypothyroid symptoms.



I am surprised because FT3 is so low. I don't have an opinion about FT3/rT3 ratio. I don't know enough about it.


You should find out more about it. You are giving opinions without knowledge.



Don't tell me what to do. I haven't given an opinion about FT3/rT3 ratio.


Actually, you did give an opinion regarding rt3 in my first post on this forum.

You said that I don't have an rt3 issue because my rt3 was mid-range.

Please do not respond to my posts if you are unwilling to do the research.


rT3 is mid-range so you don't have a rT3 issue.

TSH was suppressed, FT4 is less than halfway through range and FT3 is only 25% through range but FT4 and FT3 will change now you are taking NDT. FT4 will almost certainly drop, perhaps even below range but as long as FT3 is good around 3.4 - 4.4 it is fine. FT3 in the upper range usually means TSH will be suppressed.

B12 437 is unlikely to be deficient but if you have symptoms of deficiency in b12deficiency.info/signs-an... go to healthunlocked.com/pasoc for advice.

VitD 37ng/ml is sub optimal. Optimal is between 40-60ng/ml so you may want to supplement 1,000iu D3 daily.



What is it you don't understand about "I have no opinion about rT3/FT3 ratio"?

Interpreting a rT3 result within the lab ref range as normal is not the same as interpreting rT3/FT3 ratio.

I remind you that "This is a patient to patient forum and no one, including the Admin team, on this community should be assumed to have medical training of any sort.

Everyone is only speaking from their own experience, that of friends/family or other people they may have spoken to."

Please remind yourself of posting guideline #6 when you respond to members.


You may be assured that I will not be responding to your posts other than in my capacity as administrator.


Oh dear. Is this an adult forum or a school playground? I know that the admin staff have no medical training etc but I must admit that one or two do give the impression of superior knowledge.

If, in general, we are claimiing that we should be medicated according to how we feel, not to a set of numbers, squabbles like this need not arise.

1 like

I guess that was all I was saying. I feel good at these low numbers, which seems counter-intuitive. The title of my post had a question mark. There are certain ideas that are not as welcome here, evidently.


I'm sorry to say that you are correct.

People will insist on quoting the views, experiences and opinions of every man and his dog as fact.

I am quite concerned by the 'facts' being advanced. You cannot mitigate the folly of this with a disclaimer about your medical background and qualifications. I recently left the forum because of this issued. I then rejoined with a different name as I thought perhaps it was me being over sensitive.

To my amazement one person posted a completely contradictory statement about my medication to that which she'd made to my other name.

The forum is very supportive to many people and I for one have been very grateful.

However this adamant and rather arrogant desire to be right is what gets internet fora a bad name.

1 like

I am confident enough in what I have read and experienced not to be swayed by a title after a name. (Dr, MD, admin, etc)

I thought that my experience might benefit many others who have a similar issue.

I agree that the forum is very useful because of patient experiences. And there are many very helpful admins that give solid advice. The big thing I've gotten out of this forum is to make sure that your iron, B12, D, etc are all good, and that everyone has a crappy doctor/endo, which is comforting:)

I think what happens is that the opinions or perceived opinions of the actual medical professionals that contribute to this forum are fiercely defended.

The irony of this schoolyard fight is that it got this post into the top posts for the day and got it more exposure. Amen to that, lol...

1 like

Scott, could you please explain the figures within your table:

Is 76 and 18 levo doses ie you've added NDT 2grains + 76 mcg of Levo? and later this was reduced to 18 mcg Levo + 2 grains of NDT?

1 like

Sorry, the 76 is the t4 content of the 2grains of NDT. 18 is the t3 content.

I switched from levo/cyto to NDT.


Great! Thanks, Scott. Just what I needed as a clarification.

The short answer to your question is a big YES!

I looked at your RT3 levels in July. 19 is a very high level and indeed you'd feel awful with those levels.

Rule of thumb: when we look for the optimal T3, the levels ought to be at the higher end of the range.

The same is reversely applicable for RT3. They ought to be nearer to the lower end of the range.

In general, as you probably know, in the event of too much T4 circulating in the blood, RT3 acts a break to protect the body from a surge of T3.

Previously, 104 mcg of Levo + 10 mcg of readily made T3, as your daily dose, was way more than what you needed and have prompted high RT3.

By lowering your dose to 2 grains of NDT (lower T4 and lower T3 from before), you have lowered the substrate of T4, and accordingly, your total circulating levels of T4 dropped as well.

Now, with the new levels of RT3 being under 9, your body is relieved and has ceased to be in the fight mode (RT3 increases Cortisol) as when it was on the higher dose and was able to flush the excess of RT3.

By doing so, your T3 levels however they may have been reduced, they are now actually reaching your cells whereas before all high levels of RT3 were sitting on the receptors and preventing the T3 from entering the cell.

You are on the right track and the little increase to 2.5 grains will hopefully make you feel even better.

Finally, if I may add, to maintain low levels of RT3, you have to have good circulating iron in your blood. Low iron or anemia will cause your body to make more reverse T3 than T3.

Low levels of Vitamin D, B6, B12 selenium, Zinc, and inflammation can all cause High Reverse T3 as well.

I hope this helps for now!


We are definitely on the same page on this. Just a couple of comments.

I have made sure that my D, B6, B12, selenium, zinc, and iron are being adequately supplemented. I have had problems converting for a long time and made every effort to eliminate these causes.

As for the change to 2 grain NDT...My ingested T4 went from 104mcg to 76mcg, which is a reduction. My ingested T3 went from 10 mcg to 18mcg, which is an increase.

My lower serum levels of T3 may be attributable to an overall reduction in converted T3 + ingested T3. Or possibly, as you mentioned, now that T3 is actually able to occupy receptors previously occupied by my former abundance of rT3, serum levels drop because those molecules are taken out of circulation. Yippee!

Everything you said is spot on. Now, is there any cold hard research that we can back it up with?


Did you take the labs for each med at roughly the same time of day? For example, did you take 10 mcg T3 one morning with your levo, and then test the next morning, 24 hours later? And same with the NDT? If not, what was the difference in lapsed time from taking your dose to testing?


Labs were done late morning in both cases, no fasting.

Levo and 5mcg Cytomel taken 7am the morning prior, and 5mcg taken at noon the day prior. (so, almost 24 hours from last dose of anything)

As for the NDT, the whole dose was taken at 7 am the day prior to labs.


Yes, plenty is out there. This resume is a synthesis of lots of reading and analysis.

I will do that extra mile for you and we'll try to compile a few easy readings and direct message them; only to for you to rest assured.

How about that for a deal/help? :-)

Keep up those levels checked and topped up when needed. Have you been taking any selenium? something for you to consider adding to your daily cocktail if you have not been doing so.

As for your additional comments.... it is the too much of T4 that is the problem and causes RT3. Other than the conversion issues, it is a major reason as to why many patients do not do well on T4 alone. Overall, NDT is also known to reduce RT3.

You are on the right track with your endo! Keep him/her :-)

1 like

I have read extensively on the subject.

I do not subscribe to the theory that rt3 blocks receptors for lengthy periods of time. It doesn't need to, as you body keeps making more each time you too much t4 in your mouth.

But it does make sense that rt3 competes with ft3 for receptors.

Then it is a simple matter of math as to what your chances of getting energy to your cells is. (depending on the affinity for receptors, which is being debated?)

But there are people out there that believe that rt3 does not occupy t3 receptors...that rt3 has receptors all its own. (in the liver, but that's a whole different subject)

There are people that believe that rt3 is simply a disposal pathway for t4 and that it has no other negative impact on cellular activity than the absence of the t3 it didn't become during conversion.

So, how do you handle those objections?


From what I have read, I have reasons to challenge that.

1/ RT3, a biologically inactive ‘mirror image’ version of T3. Note the use of 'mirror image" and make your interpretation.

2/RT3 binds to membrane receptors and produces hypo-metabolic effects.

3/ RT3 inversely correlates with physical performance scores and the T3/RT3 ratio is a useful indicator of tissue levels of thyroid hormone.

4/ Reverse T3 is an excellent marker for reduced cellular T4 and T3 levels not detected by TSH or serum T4 and T3 levels.

I hope this is helpful!

1 like

Very much so!

And I got your link to the article written by the person they were quoting. Ha, ha...that's too funny.



Glad to be able to help!

You are welcome!


rT3 is NOT a mirror image.

It results from a different position iodine atom having been removed to the one that results in T3.

The obvious mirror image of what we usually call T3 would be D-triiodothyronine.

The images here show more clearly than words alone:


1 like

There is a post below challenging the mirror image assertion. Just wanted you to see it...


Thank you, Scottbnk.

I saw it and I also saw the assertive shout that is NOT!

It appears that this has become a bit personal and let me prove it.

If you looked at this link


Greygoose, 20 days ago, presented some accurate and similar information:

“This is done by removing the 'wrong' iodine atom, so that the rT3 molecule is a mirror image of T3 - hence the name: reverse T3.

The rT3 molecule cannot get into the cells, meaning that the body has less T3 and therefore has to slow down. This is a normal safety procedure to preserve life.”

Separate from that here is my reply and I shall use exactly the same tool/link presented by the previous poster.

By definition, a "mirror image" or object which is identical in form to another, but with the structure reversed, as in a mirror. (Note the word reversed).

Now, let's examine the molecular structure of T3 and RT3 provided within helvella's link.

Actually, as you can see for yourself, this came to confirm that RT3 is the "mirror image" of T3 rather than refuting it, and I will not comment on the other information that he/she has also presented.

I shall stop at that and present everyone with all the best wishes for a lovely weekend.

1 like

You may also like...