Liver-produced hormone that constitutes the main circulating regulator of iron absorption and distribution across tissues. Acts by promoting endocytosis and degradation of ferroportin, leading to the retention of iron in iron-exporting cells and decreased flow of iron into plasma. Controls the major flows of iron into plasma: absorption of dietary iron in the intestine, recycling of iron by macrophages, which phagocytose old erythrocytes and other cells, and mobilization of stored iron from hepatocytes. Interacts with SLC40A1; this interaction promotes SLC40A1 rapid ubiquitination. Highly expressed in the liver and to a much lesser extent in the heart. Secreted in blood (PubMed:15124018). Regulated in response to changes in circulating iron concentrations, iron stores or the development of inflammation and iron-restricted erythropoiesis. Down-regulated following anemia induced by hemorrhage or hemolysis: down-regulation is mediated by ERFE (PubMed:12370282, PubMed:24880340, PubMed:15124018). The induction of upon inflammation is mediated by IL6 (PubMed:15124018). Belongs to the hepcidin family.