
Fasting and Thyroid Function: Why Active T3 Drops and What Reverse T3 Means
A drop in active T3 during fasting is often mistaken for hypothyroidism, but shifting T4 to reverse T3 is an adaptive energy-preservation mechanism.
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A drop in active T3 during fasting is often mistaken for hypothyroidism, but shifting T4 to reverse T3 is an adaptive energy-preservation mechanism.

One number is used to rule the whole system in or out, and it sits two steps upstream of anything you would actually feel.