Reverse T3 (rT3)

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How High Reverse T3 Causes Low Thyroid Symptoms. Dr Hagmeyer

Reverse T3 How to Lower it

Your body  uses a portion of the T4 to create Reverse T3 (RT3), another inactive form of thyroid hormone, but one that can attach to the receptors for Free T3 in order to slow down your metabolic processes.

If RT3 is high – you are likely converting too much T4 to RT3 and not enough to FT3, which can cause hypothyroid symptoms even if your TSH and T4 levels are optimal. In addition,  look at something called a RT3/FT3 ratio and that should be less than a 10:1 ratio.

The body, especially the liver, can constantly be converting T4 to RT3 as a way to get rid of any unneeded T4. In any given day, it’s stated that 40% of T4 goes to T3 and 20% of T4 goes to Reverse T3.

But in any situation where the body needs to conserve energy and focus on something else, it will change the above percentages, changing the conversion of RT3 to 50% or more, and the T3 goes down, down. Examples are emotional, physical, or biological stress, such as being chronically or acutely sick (the flu, pneumonia, etc), after surgery, after a car accident or any acute injury, chronic stress causing high cortisol, being exposed to an extremely cold environment, diabetes, aging, or even being on drugs like beta blockers and amiodarone. But there’s another reason for thyroid patients. Read on.

On top of the chronic stresses of  life, there are three common physiological reasons which thyroid patients in particular have noted, with the first two related to the adrenals (low cortisol, high cortisol), and the third related to  iron levels. Even low B12, Lyme, chronic inflammation and other health issues can cause it.

1. When biological stress is excessive, such as being on the inadequate treatment of T4-only or being held hostage to the  TSH lab test (both which keep you under-dosed or hypo), patients have noticed their adrenal glands producing high amounts of cortisol to help one cope with ongoing hypothyroidism and lingering symptoms and conditions.  The excess cortisol inhibits the conversion of T4 to T3,  and instead produces even larger amounts of RT3, creating an RT3 problem.
2. When biological stress is ongoing,  the adrenals will eventually produce less cortisol (ask “adrenal fatigue” or “adrenal insufficiency”), dropping from high cortisol to a mix of high and low, then to all low. And those low levels can cause chronic anxiety, poor coping skills, paranoia, easy nausea, sensitivity to light or sounds, psychological issues, etc.  When you don’t make enough cortisol, thyroid hormones can pool high in your blood. So your body responds by converting the T4 to excess RT3
3. When iron goes low, which is quite common in thyroid patients due to low stomach acid, your red blood cells become less plentiful (or you have enough, but they are weak and pale), and carrying thyroid hormones via your blood becomes inadequate, causing thyroid hormones to pool in your blood. The body responds by producing excessive amounts of RT3 to clear out the excess T4.

***Note that you can have either an iron problem, or a cortisol problem, or BOTH. There are other reasons you have high RT3, such as the excess inflammation and more, but the above are quite common and worthy to explore first.

There’s room to be suspicious when the Free T4 is higher in the range for a while, especially above 1.4 if using the ranges where the top of the range is 1.7. Some notice it when their free T3 goes lower (i.e. the more RT3 you have, the less T3 you will have from conversion). Even having a high Free T3 due to adrenal or iron problems  can be the beginning of also acquiring too much RT3.

Doing the RT3 lab test has given patients the best clue.