As I posted somewhere else, I have been taking my Synthroid under my tongue for five weeks as an experiment. I have not seen any difference in the way I feel. I was having trouble trying to take it at the right time before or after meals, sometimes this would cause me to forget to even take it at all. I now just put my Synthroid with my other meds and after I have coffee and toast in the morning, I take my meds and then just put my Synthroid under my tongue. I now do not have to remember when to take it. I like taking it this way and will continue, not because it is better or worse, just because it is much more convenient for me.
If you do this, write down when you start and take notice as to how you are feeling after three or four weeks.