Hi I have been diagnosed with MMN and have hypothyroid, the best things I have found to help with symptoms are b1 b3 niacin not niacinimide (note a flush is normal but I found it help with fasciculations once the flush passed) b6 b12 and omega fatty acids. Calcium Magnisium and Zinc all help as well but interact badly with synthroid and levothyroxin so avoid taking these minerals for 4 or more hrs after your thyroid meds. Good luck this info took a lot of guessing and trial and error. I wan't givven any link between low thyroid and MMN myself but am interested in you case as it sounds similar to my own.