Many of you follow my writing and understand that hypothyroidism means reduced level of thyroid hormone, dubbed “T3.”  But you probably have not heard of reverse T3.  Today I’m going to tell you why you should never ignore reverse T3, even if your endocrinologist does.
First the basics.  The hormone called T3 gives you energy, so it’s sometimes called the gas pedal in your body.  Reverse T3, abbreviated as rT3, would then be the brakes. You sometimes want to use the brakes, don’t you?  If you don’t have brakes, your body will speed away on the highway and zoom out of control, so rT3 is required as part of your body’s  push/pull balancing system.  It’s the isomer of thyroid hormone that looks like it’s the reverse (opposite) of the active T3.  Picture your left hand as your rT3 and your right hand as your T3.
If you have too much rT3, it can cause all the symptoms of hypothyroidism that you don’t want, like chronic fatigue, a sluggish metabolism, and weight gain.  This is a measurable thing, this rT3!  Unfortunately, even endocrinologists tend to ignore it, and they may fight you if you ask to have the blood test drawn.  In my opinion, that is an oversight.
But they’re not just being mean, it’s that most physicians were taught that rT3 is an “inactive metabolite” of thyroid hormone, and therefore has little to no impact on hormone balance.  Because it doesn’t activate the cell, it gets pushed under the rug.
But high levels of rT3 put you into hibernation by sitting on the cell’s receptor (the doorway to the cell) and blocking active thyroid hormone (T3) from binding.  So you can see, it’s common sense, right? If you have too many of the do-nothing rT3 molecules on your cell, then your cell can’t bind the T3 that wakes you up, burns fat, and makes you happy!
IMHO, not testing for rT3 levels is an oversight. If you’re rT3 dominant, you’re clinically hypothyroid, stressed, anxious, overweight, tired and cold! And yet your TSH and your Free and/or Total T4 levels might be in perfect range.  How would know you were rT3 dominant unless you were tested.  (I’m making a good case here, aren’t I?)
Let’s do a quick review so I know you’re with me!
Reverse T3: A Check and Balance Hormone rT3 performs a kind of balancing of the checkbook of the body. It cancels out a percentage of active thyroid hormone to bring everything to a kind of “0” level, where 0 equals harmony. To reiterate my car analogy, the gas pedal is T3 and the brakes are rT3. The process of these compounds binding to your cells takes place in milliseconds, billions of times a day.
Inactive T4 and its conversion into active T3 gives us a nice, speedy metabolism and promotes energy, beautiful and shiny hair, a content mood, and a beautiful figure. These hormones are THAT important!
Thyroid hormone regulation influences your weight, metabolism (meaning how fast you burn off that figgy pudding), respiration, pulse, and ATP (energy) production in the very mitochondria of every cell you have!
Here’s where reverse T3 comes in. Reverse T3 is a mirror image of T3. Picture again your left and right hands. They are mirror images of each other.
In our bodies, about 40% of inactive T4 is converted into T3, powering our metabolisms and keeping us energetic and slim, and 20% is converted into rT3 to make sure we don’t burn up all calories and end up a nervous, bone-rack of a wreck.
So, the rT3 is there as your check and balance. It clears out excess T4, keeping you in homeostasis, perfect balance. It puts the brakes on if your gas pedal is floored.
Problems You Might Experience
1. Low T3 
If you have too little Free T3 relative to T4, you get hypothyroidism. Therefore, you experience weight gain, fatigue, joint and muscle pain, depression, and a tendency to feel cold.  The reason for this is you aren’t producing enough heat or ATP energy in your cells!
2. High T3
Too much T3 relative to T4 will cause the opposite, as in hyperthyroidism. This causes you to feel jittery, worried all the time, anxious, nervous, irritable, and sometimes hot or sweaty, rather than cold. You could be diagnosed with Graves’ disease if you are found to be hyperthyroid and have high antibody titers.
3. High rT3 
Too much reverse T3 and you get the same effects as hypothyroidism (low T3) as shown in situation #1 above. This is because the high levels of reverse T3 block your cells’ ability to get fed by your “wake-up and feel great” thyroid hormone called T3.
Reverse T3 isn’t bad. I want to make this point crystal clear.  Reverse T3 is not the enemy (unless it’s very high), because it keeps you feeling just energetic enough without you sailing into full on hyperactivity/stress mode (which you don’t want, because stress is the archenemy of any and all hormones, including cortisol and estrogen, both of which cause belly fat gain and extreme fatigue).
In fact, this whole mechanism in our bodies is there to protect us from starvation, as it did for our ancestors in times of famine or hiding out from saber-toothed tigers. Picture yourself stuck in a cave, clad in a fur sarong like Captain Caveman, heart a-pounding and a bubble over your head saying, “Is that ugly thing still outside smacking its lips?”
So, a too-high rT3 level in the body, is bad, creating reverse T3 dominance and a poorly functioning thyroid gland.
And here’s where things get really interesting. Back to my ancestral-slowing-of-the-metabolism-in-times-of-peril story. Researchers have recently learned that rT3, not cortisol, may be the real cause of our inability to lose weight, and the reason why we gain or regain weight so quickly after a diet. This comes as a surprise to most physicians in the medical community as cortisol has been considered the main “belly fat” hormone for decades.  We’re learning now that it’s more likely high rT3 that drives the yo-yo spike in weight, another reason to consider T3 medications, as opposed to T4 (i.e., Synthroid).  T4 doesn’t always metabolize to T3, you see.  This is all covered in my book, Thyroid Healthy.
When you diet, especially if you suddenly and drastically reduce your food intake, you create a mountain of physiologic stress, which adds to the terrible emotional stress caused from the restriction of everything you love! This physiologic, or better termed “metabolic” stress, cases your rT3 to rise, reducing your thyroid activity and slowing your metabolism which… voila!  Causes you to literally pad your vulnerable organs with fat! Picture padding around your belly, where a lot of your organs are – this nice layer of protective fat padding is called “belly fat” and it hides out there in case a tiger attacks!
High rT3 is also one reason you regain weight so quickly after a crash diet. In fact, researchers have basically found that whenever we humans lose weight, our body fusses about it, basically rebels against us, and tries to regain any weight lost during the sudden crash diet, which it perceives as a famine.  In fact, the more extreme your caloric reduction, the higher the spike in rT3 from the forced starvation.
Did you know rT3 dominance can impair your ability to build and repair muscles?  If you have high rT3 (and again, you can measure this with a blood test) it causes fat-burning muscles to wither, so when all is said and done, you will be bones with flabby fat, and very little muscle.  This is why I’m adamant about you testing for it, and fixing it if it’s high.
How to Find Out if Your rT3 is Too HighI literally wrote the book on this topic, and hosted a world-wide thyroid summit event in 2014. I’ve interviewed the best thyroid experts in the entire world.  More than that, I’ve dealt with this problem myself, and for many years I have been very healthy and so I can speak to this situation with ease, and I’m confident I can help you.
Over the years, I’ve gotten countless emails from some of you saying “I could not get my physician to order this lab test for me.”Again, most physicians are taught rT3 really doesn’t do anything in the body and, therefore, they rarely measure it and may be resistant to running tests.
But high levels suggest that you are not “thyroid healthy” and that you could very well be suffering with all the symptoms we’ve been discussing, especially fatigue and weight issues. It could also mean (and this my fear for you) that you get diagnosed with a mental health disorder such as Generalized Anxiety Disorder, Insomnia, Bipolar Disease, Heart Disease or some other problem that requires a big drug!  All the while, your thyroid hormone gets ignored because “That’s not a big deal, let’s try a new drug that’s out to help you with [insert new bizarre symptom here] and we’ll see how you feel in 6 months!”
Do you hear that? Am I right?  So, it is extremely important you get tested for rT3 along with your regular thyroid hormone profile.
Any doctor can test this, it’s available by Quest, Labcorp, and every other lab I know of.  But if you encounter resistance, you can certainly order them yourself from direct-to-consumer labs, which have popped up in the last few years. Because I’m a practitioner, I even have an affiliate connection where you can order tests, although you need your own local laboratory, and your own doctor to discuss it with.
Important: On Thyroid Drugs and rT3 DominanceIf you have high levels of rT3, I suggest you NOT use the T4 drugs (Levothyroxine is the generic), because it tends to break down into even more rT3 (as opposed to T3). As a result, some of you still feel awful and hypothyroid, even though you never miss a dose of your medicine.
Remember that. Because if you have high levels of rT3 and you take T4 drugs, you’ll generate even more rT3, instead of the biologically active T3 which makes you lose weight, look beautiful, and live the life you imagine.
What if rT3 is high? What Do You Do Then? You can, in fact, lower rT3 naturally!
How to Lower rT3 Naturally and Get Slim and Gorgeous AgainThe following information could make all the difference between a slim, healthy, energetic you and cold, tired and worn-out you.
These are some ways to lower rT3 naturally:
1. Increase selenium in your diet with Brazil nuts or seafood, or through supplementation. If you’re shopping for supplements, bear in mind that selenomethionine is more natural than sodium selenite.
2. Support your liver and consider a liver cleanse or supplements like milk thistle, glutathione, or artichoke extract. Some over-the-counter analgesic medications that go through the liver for their metabolism can weaken the liver over time.
3. Reduce or eliminate drinking, smoking, and refined foods which hurt the liver and spawn free radicals. These habits also destroy the fragile lipophilic cells of your colon, your lungs, brain, heart, pancreas and your thyroid.
4. Ask your physician for a trial run of a T3 medication, or NDT which is a combo of T3 and T4 medication. The point is to get away from a T4 drug and get on to a T3 containing medication. The T4 drugs (levothyroxine) tend to preferentially break down into more rT3 instead of bioactive T3.
5. If you’re on a T4/T3 combo drug like an NDT drug already and your levels of rT3 are still high, then consider switching to plain T3 as in compounded T3 by a compounding pharmacy, or Cytomel, a drug sold in most pharmacies in the US. Either way, it might be time to switch from NDT natural desiccated thyroid to a plain T3 medication for a while for the same reason as above. This is a decision that is best determined by your medical physician and your lab values for free T3, total T3 and rT3. You’d know if plain T3 works within a month, it’s that fast.
6. Consider one or two adrenal-supportive herbs or adrenal-loving vitamins. There are many, I don’t know which ones are right for you so I’ll name a bunch. You can consult the oracle Dr. Google (lol!) and learn about these and then buy them at any health food store. I would recommend you consult your physician first to find out his/her opinion about which is right for you specifically: Astragalus, rhodiola, beta sitosterol, ginseng, ginger, B vitamins (especially pantethine), schisandra, eleuthero, ashwagandha, turmeric/curcumin or L-theanine.
What is a Healthy rT3 Level?If your thyroid levels are in perfect balance, your rT3 levels should be lower than 15 ng/dL or 150 pg./ml.
A whole healthy thyroid panel would look like this:
  • rT3 < 15 ng/gL also expressed as <150
  • Ferritin 70=90 mg/dL
  • TSH .5 – 1.5 mlU/l
  • Free T3 = 3.5-4.3 pg/dL
  • Total T3= 140-175 ng/dL
  • Free T4 = 0.8-1.8 ng/dL
  • TPO antibodies less than 20 IU/mL
  • T3/rT3 ratio should be > 2
Now that you have this information and a new consideration, you can demand excellence from your health care provider. You can have an intelligent conversation about one simple lab test, and understand what it all means to you.  I’d like to empower you and all individuals experiencing thyroid dysfunction with the knowledge and wisdom to feel healthy and strong again, as well as happy, warm, and skinny! That’s what your thyroid can do for you, so please share this article with anyone you love.