Re: what's the difference between ferritin and iron?
Low ferritin is a precursor to anemia. So your serum iron levels can be normal while your storage protein, ferritin is very low.
Low ferritin will interfere with thyroid hormone conversion as well as reducing the activity of thyroid peroxidase. In short, it's essential for normal thyroid metabolism.
Low ferritin will mimic hypothyroidism, causing many of the same symptoms.
So getting your ferritin tested and the levels up to the 70-90 range is essential to successful thyroid hormone replacement.