If t3 only doesn’t work in the long run then you’re probably going to be the type that responds better to t3+t4. Don’t listen to anyone else’s ideal ratio, you’ve got your own unique mix of deiodinase activities + micronutrient assimilation
I respond to neither T3 only nor T4+T3 lol. I think I know why, all my carbs are going to lactic acid instead of all the way to CO2, and that's spiking my adrenaline and cortisol, preventing T4 to T3 conversion and not letting me build up my cholesterol levels. But I don't know how to fix it, I've tried everything I know besides leaving everything behind and moving to the mountains for the pro-CO2/anti-lactic acid effect of high altitude.