Increasing and decreasing phases of ferritin and hemosiderin iron determined by serum ferritin kinetics.

We attempted to clarify the mechanism of the storage iron metabolism. A new program of serum ferritin kinetics was applied for studying the increasing and decreasing phases of ferritin and hemosiderin iron in iron addition and removal in patients with a normal level of iron stores or iron overload. The change of ferritin iron in response to iron addition and removal was rapid in the initial stage, but it was slow later. In contrast, the change of hemosiderin iron was slow in the initial stage, but it became rapid later. These changes of ferritin and hemosiderin iron suggest that the turnover of ferritin iron is preferential to that of hemosiderin iron, and that the initially existed ferritin iron is gradually replaced by the ferritin iron recovered by taking iron from hemosiderin in iron mobilization. The crossing of the increasing curves of ferritin and hemosiderin iron in iron addition indicates a switching of the principal storage iron from ferritin to hemosiderin. The crossing point shifted toward a higher storage iron level in the increase of iron deposition. Iron storing capacity can be increased not only by the transformation of ferritin into hemosiderin, but also by the expansion of cell space as seen by hepatomegaly in hereditary hemochromatosis. The amounts of hemosiderin iron exceeded ferritin iron in all 10 patients with chronic hepatitis C even though they had normal storage iron levels. This suggests it is difficult to store iron in the form of ferritin in chronic hepatitis C.