Further to a recent post by HealthStarDust on TRAb results and a discussion with tattybogle and pennyannie as to whether having blocking ABs dominating would give high or low TSH, I posted a question on Elaine Moore forum. The following is her reply :-
About 20% of patients who move into remission using meds or naturally have a 20% of moving into hypotjyroidism. You're right in that the cause is blocking TSH receptor antibodies. All TSH receptor antibodies are recognized by the pituitary as if they were TSH. So the pituitary thinks you have enough TSH and stops secreting TSH normally. This causes a falsely lowered TSH result. I have the same problem with my TSH staying at <.07 even if I'm hypothyroid. That's why we say TSH is misleading in Graves' disease. You want to be closer to the high end of the range for FT4 and midway between the middle and high ends of the range for FT3.