His situation mocks mine entirely after I had RAI and it took months to develop.
Having high (er) liver enzymes is pretty common with RAI patients. Regardless what's been said, the whole body can be effected by this.
Acid reflux, indigestion is commone in the PH imbalance that RAI caused too.
In most cases - your father probably is not entirely coverting his medication properly and most likley won't. If his medication is a T4 only nmed - and he is an RAI patient - it seems common that the T4 hormone medication is not going into the T3 hormone he needs to feel optimal.
In a nut shell - he most likely is still T3 hypothyroid to a degree, hense, his body is slowing down causing issues.
Note: in my case the metallic taste was around for quite some time after I had RAI and then what happened next for me was horrifying. I developed the worst burning tongue imaginable and lasted months.
Your dad must get better labs and I can only assume he is not being medicated by the right ones.
Free T3 lab and Free T4 lab is very important and his doctor has to treat him with those labs to really feel better. I found switching my meds from T4 to T3/T4 combo meds improved my condition also.
another thing that improved my condition was taking acidophillus to get my digestion track working right again.
The metallic taste might be more reflux related. I had bad relfux up till two years ago when I was on T4 meds only, with the metallic taste in the morning. My liver #'s from a total blood physical were good. But my biliruben was elevated (many have this) - that is related to liver..
Acidophillus, and glutemine and lots of veggies while backing off from red meat and gluten, helped reflux. Adding T3 made it even better.