Reverse T3 is a mirror image of the active thyroid hormone T3 that binds to the same receptors but shuts them down as a protective response to stress. Standard thyroid tests miss it, but elevated rT3 can explain chronic fatigue and brain fog in long COVID and other chronic illnesses where normal thyroid panels look fine.
Reverse T3. It's the same as the T3 that turns on everything, only it's a mirror image. And so when it goes and binds to the outside door receptors or goes and binds to the inside receptors at your mitochondria or your DNA, guess what it does? It shuts them off. Now, this is a safety mechanism your body has developed. We don't find a lot of help in testing reverse T3 in healthy people, but in chronically ill people, long COVID patients, and people who have had a lot of, you know, heavy drug therapies for, you know, cancer or hepatitis or something, testing reverse T3 can be very helpful because it can say how stressed is the body and how much does the body try to protect your cells. The problem is it can go too far. I developed chronic fatigue, other cells don't work right, my brain slows down. But then, you go to your doctor and they test your TSH or your T4 and it looks normal, or your T3 could even look normal. But, it's because you're chronically ill, they didn't test the reverse T3.
