Thanks for your input Alfosina!
I have in Naturethroid since I started my treatment years back. When there was a shortage of both NT and Armour I freaked out. Suddenly Armour started to be more available than NT and my doctor put me on Armour at the same dose I had been in NT.
Armour had been reformulated and for me personally the change was not favorable, I felt worse on Armour than in NT, probably I felt I needed a higher dose, but I did not continue experimenting because NT started to be available again and I did not think it twice.
I hope it helps, Armour and NT are supposed to be the same strength, but sometimes your body might react differently because, as you said, of the fillers.
One other note I want to stay with NDT! I am not crazy about the synthetic options!