I would make another vet visit - get a blood test and see how his metabolism is. A vitamin B12 injection (relatively inexpensive) might help give a bit of a boost too for this issue. I am no reptile vet but in humans.. Anemia can cause low iron levels/the enlarged liver.. Both symptoms of the same. Renal failure is a big cause of anemia which would be a secondary problem if thats the case.. What food are you feeding your ig?