Iron homeostasis: fitting the puzzle pieces together.

Here, recent insights into iron homeostasis are highlighted. Three studies demonstrate the importance of the IRE-IRP system for enterocytes in balancing extracellular iron demand against cellular iron requirements, show that the hemochromatosis protein HFE exerts its iron-regulatory activity principally in hepatocytes by modulating the production of hepcidin, and provide strong support for a proposed mechanism of transcriptional regulation of hepcidin through a signaling cascade initiated by holotransferrin displacing HFE from transferrin receptor 1.