Reverse T3 dominance could be the reason why you still have hypothyroid symptoms even though you are taking thyroid medication.
Or why you struggle to lose weight even when your thyroid labs are "normal."
Never heard of reverse T3 dominance? Most people haven't, including most doctors.
High levels of reverse T3 could be slowing down your metabolism, reducing thyroid function at the cellular level, and causing multiple symptoms of hypothyroidism.
The purpose of this article is to inform you about reverse T3 - its purpose in the body, what causes it to get elevated, how to test for it, and how to reduce it back to optimal levels.
Let's get started...
The thyroid gland primarily produces T4. That is thyroglobulin with 4 iodine molecules attached to it.
T4 is the inactive transport form of thyroid hormone. In order to be used by the body, an enzyme called a deiodinase must cleave off an iodine molecule to convert it to T3.
T3 is the active hormone that can then interact with cells of our body and turn on certain cellular functions.
However, T4 can also be converted into reverse T3.
Reverse T3 will also bind to the cellular thyroid receptors. However, it doesn't trigger any cellular reactions.
So basically reverse T3 serves as a "brake" to our thyroid system.
The production of reverse T3 is normally not a bad thing. It gives our body another way of regulating our energy production and output.
Reverse T3 production will increase during times of extreme stress.
That makes sense if you think about it closely.
For example, if you have an acute infection such as pneumonia, a kidney infection, or you've had something like a car accident and have suffered multiple injuries, your body needs to turn down the metabolism to conserve energy so it can be used to fight the infection or injuries.
This system works very well for such acute situations.
There is actually a medical term for this condition - Euthyroid sick syndrome.
However, with the onslaught of chronic conditions and resulting inflammation in our society, it has also become extremely common outside of the acute setting of a hospital.
People that are under extreme stress develop this condition which results in a high reverse T3 level, low free T3 level, and a normal TSH and T4 level.
Does this sound familiar? Do your labs look like that?
In 20+ years of private practice, I have never seen this diagnosis given to a patient that wasn't in the hospital.
But if you look at studies like this one, something as common as a calorie-restricted diet can raise reverse T3 levels and lower free T3 levels and cause other symptoms that "resemble euthyroid sick syndrome."
So what is going on? What causes the reverse T3 levels to increase (reverse T3 dominance)?
Let's talk about it more...
From what we have discussed so far, unless you are acutely ill or have suffered a major injury of some sort, you want your reverse T3 level to be as low as possible.
Does an elevated reverse T3 cause any symptoms?
The answer is yes!
The symptoms will be the same as you would think of with someone with an extremely slow metabolism (which is what reverse T3 dominance causes):
If you have any of these symptoms, it's important to get your reverse T3 level checked and follow the treatment instructions that I will discuss below.
What are some of the most common causes of reverse T3 dominance?
If you have one or even more of the above issues, it is important for you to be tested for reverse T3 dominance.
Testing for reverse T3 dominance is readily available but may be hard to get ordered.
You will need to see a doctor that has a full understanding of the thyroid and doesn't just depend on the TSH to determine thyroid health and function.
It is critical that you get a complete thyroid panel. I discuss this more in this article.
This will include the TSH, free T4, free T3, reverse T3, TPO antibodies and thyroglobulin antibodies.
As you can see from this graph, when reverse T3 dominance occurs, the TSH level will remain normal the vast majority of time. So will the free T4 level, which is the other lab test that most conventional doctors will order.
The lab tests that will show an abnormality the quickest will be the reverse T3 level and the free T3 level. You can see that as the reverse T3 levels rise, the free T3 levels fall.
Even though your TSH may be normal, your thyroid is not working well at all!
That is why the reverse T3 and free T3 are absolutely the most important thyroid tests to get when assessing for reverse T3 dominance.
You will also want to check the ratio of reverse T3 to free T3 to get an idea of what is happening in your cells.
Normally you want your free T3 to be as high as possible and your reverse T3 to be as low as possible.
I consider a reverse T3 > 15 to be abnormal.
It is possible to have a normal free T3 level but still have a very high reverse T3. That is why the ratio is important.
To get the ratio, divide your free T3 by your reverse T3. The ratio should be >0.20.
Any number less than 0.20 indicates that you have too much reverse T3 and you need to take steps to lower it.
Okay, so you've gotten the necessary lab tests, and your reverse T3 level is > 15 and/or your free T3: reverse T3 ratio is < 0.20.
What can you do to decrease your reverse T3 dominance?
The single most important thing is to identify the root cause. This is always the primary goal of functional medicine.
If your diabetes is out of control and you don't change your diet and lifestyle, your reverse T3 will not decrease.
If you are in a toxic job or a toxic relationship, you will never get your cortisol levels in the optimal range which will prevent your reverse T3 level from dropping.
I could give several other hypothetical situations, but I think you get my point.
Focus primarily on the issues that you know you have FIRST. Then consider some of the other treatment options I will discuss below.
The quickest way to reduce reverse T3 levels is by using pure T3 hormone.
This includes short acting T3 such as Cytomel or liothyronine, but also sustained release T3 from compounding pharmacies.
This is so effective because you are able to skip the conversion step required with medications that contain T4 such as Synthroid and levothyroxine.
Your body can't make reverse T3 unless it has T4. If you remove the T4, the reverse T3 levels will obviously drop.
When you give T3 only medication, it will result in the free T3 level rising, T4 level dropping, reverse T3 level dropping, and the TSH level dropping.
When on this therapy, it is very important to monitor your reverse T3 levels closely, usually every 1-2 months.
Typically the reverse T3 level will drop below 10 within 2 months (assuming you are on enough T3).
This is by far the fastest way of reducing your reverse T3 dominance, but if you don't identify and correct the root cause, it will just go back up.
By the way, natural dessicated thyroid (NDT) medications such as Armour Thyroid, Nature-throid, and others may not be adequate to lower reverse T3 levels.
They are still about 80% T4, which may still provide too much T4 that can be converted to reverse T3.
If you are on an NDT medication, you may need to reduce the dose for a couple of months and add T3 to lower the reverse T3 levels.
Again, it will be imperative to identify the root cause of your reverse T3 dominance, or else the reverse T3 levels will go back up once you return to your typical NDT dose.
Every patient with a thyroid issue is going to need one or more supplements.
When you have low thyroid you produce less stomach acid which results in less nutrient absorption.
I discuss many nutrient deficiencies and supplements here, but for this article I will only mention those that help with conversion of T4 to T3.
The primary nutrients that have been shown to increase this conversion are zinc and selenium. Increasing conversion of T4 to T3 means less conversion to reverse T3 which will lower its level.
My preferred supplements are below:
Why I Like It
May reduce antibodies in patients with Hashimoto's
Also acts as an anti-inflammatory
May help reduce anxiety symptoms
Helps boost T4 to T3 conversion (helpful in those with high reverse T3)
Who Should Use It
How to Use
My Recommended Brand and Product
Why I Like It
Many people are deficient in zinc
May help with T4 to T3 conversion
May increase cellular sensitivity to thyroid hormone
Has anti-inflammatory effects
How to Tell if You Need It
How to Use
My Recommended Brand and Product
Most hormones in the body work together.
When there is a change in one hormone, it will affect other hormones as well.
Hypothyroidism leads to a state where it is easy to develop leptin resistance and insulin resistance.
Conversely, leptin and insulin resistance slow metabolism and increase inflammation which increase reverse T3 production, which makes losing weight almost impossible.
Very high reverse T3 levels are almost always found with elevated insulin and leptin levels.
That's why you need to request a fasting insulin and leptin level if your reverse T3 is > 15.
You will not be able to get your reverse T3 level down and keep it down if you don't also address the leptin and insulin resistance.
You can read more about how to do that in my article here.
Inflammation is a vague concept.
We all know that excessive or prolonged inflammation is bad, but what do we do about it?
It is hard to measure and even harder to treat.
However, it's important to identify and address because inflammation directly increases conversion of T4 to reverse T3.
The lab tests that we use to measure inflammation in the body are nonspecific, meaning they do not tell us what is causing the inflammation.
If they are elevated, it can still indicate to us that inflammation is high in the body and we need to identify the source of it.
The primary tests that indicate inflammation are:
If you have high levels of inflammation AND high levels of reverse T3, you can safely assume that inflammation if causing or at least worsening your reverse T3 dominance.
The next step is to identify the source of the inflammation.
In hypothyroid patients, the source of inflammation is usually from one of 3 issues:
If your CRP or ESR levels are elevated, you should look closely at these 3 common sources and address them.
If you don't know the source of your inflammation, you can still consider some supplements that help reduce inflammation by improving the detoxification of the body, primarily in the liver:
Just blindly treating inflammation is far from ideal but can be helpful if you can't identify the source of your inflammation.
Without getting overly technical, doing 4 basic things can make a huge impact on your health, including your reverse T3 levels:
Just doing these 4 things alone will do more to bring you back to a state of health than anything else we have discussed.
On the other hand, if you do everything else that I recommend in this article but neglect these 4 things, you will not be successful and your reverse T3 dominance will continue.
I realize these things are easier said than done, but they have to be a primary focus for you to have success.
By the way, reverse T3 is an important component of our thyroid hormone system.
Decreasing reverse T3 levels are not harmful in the short term and can in fact be helpful.
However, persistently low levels of reverse T3 increases the risk for hyperthyroidism if left suppressed for a long time.
That's why the goal will be to "flush" out the elevated reverse T3 levels for only a short period of time and then allow the body to balance out the levels of T3 and reverse T3.
Reverse T3 dominance is a common problem for many hypothyroid patients.
It may be the primary reason why some patients have persistent hypothyroid symptoms despite being on thyroid medication and why so many thyroid patients have difficulty losing weight and keeping it off.
In order to diagnose reverse T3 dominance, you need to have your free T3 and reverse T3 levels checked.
A reverse T3 level > 15 is considered abnormal, and a T3:reverse T3 ratio of < 0.20 indicates that you have too much reverse T3.
Treatment includes taking T3 medication for a short period of time, taking supplements to improve T4 to T3 conversion, and making appropriate lifestyle interventions to reduce stress, inflammation, and leptin/insulin resistance.
Doing all of these things can help get your body back and balance and reduce your hypothyroid symptoms and weight loss resistance.
Now it's your turn:
Do you have reverse T3 dominance?
What treatments have you tried?
What has worked for you?
Leave your comments below.
Dr. Whelchel is a family physician who specializes in functional medicine, especially hormone optimization. He has over 20 years experience in private practice managing patients with various medical issues. His passion is helping patients reach their full potential of wellness and quality of life. He grew up in the Texas Panhandle where he currently lives. He is married and has 3 awesome children.