Yeah that's typical that FT4 lowers itself upon use of T3. Remember once you stop T3 your RT3 will go back to where it was unless you fixed the root cause (iron, cortisol or sickness) I take 25mcg cytomel daily and my SHBG stayed the same at mid range. Everyone is indeed different. As wrenchhead80 stated above the best method to determine if your thyroid is off is to take your basal temperature in the morning before you get out of bed... it doesn't matter what happens later in the day. All the top thyroid MD's go by basal temperature, as taught by Broda Barnes. Also your supposed to use the thermometer in your armpit. https://en.wikipedia.org/wiki/Basal_body_temperature