its not really a 'binary' process (meaning just an off and on switch) . its more like a dimmer switch, and is stable and regulatory over time.. now sure the first few days your going to be converting a lot of T4 to T3, but after a week T3 levels are stable and that daily 100mcg of T4 is more then enough and your body probably won't even use it all (so no extra stress on the liver at all)


your pituitary isn't going to be getting any signaling to produce TSH , because of the exogenous T4 your taking and because after a week your T3 levels should be totally stable .

its only if your body has a converting problem that you may run into issues (some people have a problem converting t4 to t3 so they have to just simply take t3.. but thats not all that common)