Hi there ~
I understand your concern. I believe you have sjogrens disease and having frothy saliva and itching in this condition as well as siccas is normal. If you are hypothyroid and are on levothyroxine
, it should actually make the autoimmune condition better. However consultation with an allergist-immunologist might throw light into what the real matter is.
I hope this helps. Take care and have a lovely day!