Is It Safe To Take Synthroid For Hypothyroidism?

Hello. I am a 43 year old woman in generally good health until recently. I have hypothyroidism and take 75 mcg Synthroid/day for appx 13 years. This past fall I was diagnosed from my eye doc of having Iritits. He stated that sometimes this indicates an underlying autoimmune disorder. Next time I was at mt Primary doc told him about it and he ran bloodwork. My Vitamin B12 is 1004 pg/ml. My ANA Screen, IFA was positive A. My Gastric Parietal Cells were 44.6 - greater than 25.0 for being positive. I have recently been diagnosed with an a-fib variation. My atrium chambers still beat but my heart is quivering at the same time - so I don t have the pooling effect of the blood. Caridologist states he s seen this before and may be something genetic - future tests are in the works (holter monitor and nuclear stress test). I m on 120 mg Sotalol but still having heart episodes. Regarding the gastric result - I have ALWAYS have bowel issues since the age of 20. Basically, I always have to know where the bathroom is in a public place. There is no rhyme or reason for what I eat that affects me - ANYTHING can cause me to run to the bathroom. I just do not know any different so I ve just dealt with it all my life. I understand the digestion process takes several hrs, but I tell you no lie - sometimes when I eat say lettuce or corn or something that is noticeable in the voided bowel - without having eaten something similar for a few days prior - I literally see it within 30 minutes after eating in my voided bowel - like it goes right thru me - which I know is impossible. Plus, I would be skinny as a rail and I definitely could stand to loose a few pounds. Just wondered if anyone could shed some light on these issues, especially the abnormal bloodwork.