Bobbi
What you will get from us is guesses, which isn’t necessarily helpful. There ARE situations which would necessitate more/less replacement over time. Losing/gaining a lot of weight. Going through menopause. Perhaps other situations. There have also been discussions occasionally on this board about the regeneration of thyroid tissue after surgery. I’ve not heard of it after RAI.
I will tell you that at one point in time I gradually went from 125 to 0 replacement hormone, over a few months. I was considering calling my thyroid after the Terminator, because it seemed to have come out of the RAI “truck fire” skeletal but still lethal. Then, after about three months on no replacement hormone at all, I had to go back on it, and gradually increase it over time, back up to 125. Go figure.
The only explanation I got at the time was that the disease is autoimmune; that “some” thyroid cells could still be present, functioning, and that the antibodies were revving it back up. Not a comforting thought at the time. But since then I have only had to have minor adjustments of the replacement hormone from time to time, both up, and down. I’ve been on mostly the same dose for the past 12 or 13 years.