First let me say this if you don’t fix why your RT3 is high doing T3 only meds will get it down but when you stop it it will just come back up again. I have higher RT3 from having heart bypass surgery it comes down a little every blood test I do labs every 6 to 8 weeks. Men need to understand taking T3 only can drive up your SHBG and as this goes up it binds up your Testosterone levels and your Free T falls.
Basically, for those with rT3 problems taking thyroid meds, T4 meds can make things worse and T4+T3 meds may be slightly less worse.
If you are saying that the sum of T3+rT3 increases SHBG, then the following might make sense.
Interesting implications for guys with steady TRT T levels maintaining near E2=22pg/ml who have high end TT; and FT levels fall over the years. Your points imply that this might partly be from increasing T3+rT3 levels increasing SHBG over the years [lowering FT]. If these guys are not taking any T4 meds and otherwise have [apparently] optimal fT4/fT3 levels, they do not have a option of reducing T4 levels as they are not medicating. What role could T3 meds have for such “normal thyroid” guys who have non optimal rT3 and how would TSH and T4 respond? [yes I asked about this in another thread]
We do know that SHBG increases with age, and we know that E2 often increases with age as well. This increase might be partly a result of increasing E and increasing T3+rT3 effects. If so, then rT3 issues may be a significant TRT success factor for some.