If you read experienced bodybuilders notes on T3 they recommend no more then 100mcg/day unless on gear, but some can handle 150mcg without going catabolic. For me, 100mcg assures I'm at 37,5C (normal body temperature) and I can still gain muscle just fine. I'm sure a lot of people can do just fine on smaller doses, but at 75mcg I will start producing T4, which means rT3 starts rising again.
I'm not sure what you mean by asking if I've been on thyroid meds previously. I've been on them since '98. I've tried combination, T4 only and T3 only. T3 only is the only thing that works for me. Also, why are you hung up on TSH? If your TSH hasn't tanked you're per definition not on a replacement dose. fT3 and fT4 don't mean jack if rT3 is elevated above normal. fT3 is also just what's not in use. I go by feel and by temperature. And once in a while I have to fight my doctor who thinks it's better for me to feel like crap as long as I have "a healthy TSH".
Bottom line is this - if you feel good and your rT3 is in check, that's the main objective. If that happens with armour, low dose T3, combination therapy - that's your dosage. If nothing else works, just ditch T4 altogether and go for T3 monotherapy by monitoring your body temperature and how you feel.
