Low iron, or more specifically, low ferritin, is one
of the most overlooked causes
of low thyroid function. [1] Ferritin is
the stored form of iron that is used by the cells and a better measure of available iron levels than serum iron. Iron is a component of multiple enzymes involved with cellular metabolism, so low iron means poorly functioning enzymes, and less than optimal metabolism. Those with low iron also have low T4 and even lower T3 levels.