whats the difference between t3 and t4? I read t4 converts to t3 but why not just buy t3? and does anyone know what the percentage is that t3 /t4 increases your metabolism? I know that dnp burns about 50 % more fat when used and is much better then t3 /t4 but how much of an increase do those thyroid boosters help. i think with all the normal stuff it might raise 3%.