Advances in iron metabolism and anemia: linkage of iron, calcium, and phosphate metabolism mediated by FGF23.

The relationship between iron metabolism and anemia has recently attracted attention from novel perspectives. Proper regulation of iron metabolism is essential for hemoglobin synthesis, and its dysregulation can lead to anemia or iron overload disorders. Recent discoveries have elucidated a novel secretion pathway for serum ferritin and clarified the iron-binding mechanism of transferrin, further advancing our understanding of iron deficiency and overload. Furthermore, an unexpected link between iron metabolism and calcium-phosphate metabolism has been discovered. Fibroblast growth factor 23 (FGF23), produced by osteocytes and erythroblasts, modulates metabolic abnormalities associated with chronic kidney disease (CKD) and inflammation, influencing both bone mineral metabolism and hematopoiesis. These findings offer valuable insights into the distinctions between typical iron deficiency anemia and CKD-related iron deficiency anemia. This article reviews recent findings on the roles of ferritin, transferrin, and FGF23 in iron metabolism and anemia.