T4 converts to T3 when needed, but can convert to reverse T3 under stress or inflammatory conditions to prevent hypermetabolism.

“throughout the day as el needs it weird going to convert the storage hormone into this powerfully metabolically active t3 what is not used what is not converted what el does not need we will flush out through a system called reverse t3 reverse t3 is the inactive form of t3”

“t4 is useless unless it converts to the thing that matters and that is free t3”

“T 4 is the storage hormone and it basically your thyroid releases more of that 80 to 90 percent we don't totally know maybe 9 to 20 percent of t3 so the thyroid when it's working right signals sent yo-yo you'll wake up then the thyroid goes okay gran approves a ton of t4 in a little direct t3 and then throughout the day as el needs it weird going to convert the storage hormone into this powerfully metabolically active t3”

“t4 is the storage hormone right it builds up and then when it's needed it's going to convert into t3 but when it when it doesn't or there's a threat or there's an issue happening let's say you just like get run over by a car and you've got 15 broken like limbs uh in those environments it might dial it back to avoid you from being hyper metabolic or putting more fire onto an inflammatory situation”

“instead of putting the T4 through the T3 pathway T4 will preferentially go through the reverse C3 pathway and will be completely inactivated.”