I had a total thyroidectomy four yrs ago. I have been on the same dose of sythroid for two yrs and my levels have always been stady at 2.25. Last month I was feeling off...increased irregular hear beats...so I went for an unscheduled bvlood draw. My doctor called and said my levels had dropped down to 1.12., so he increased my synthroid slightly. My question is what would cause the levels to drop after two yrs of being steady?