The liver-derived peptide hormone hepcidin is a master regulator of systemic iron homeostatis. Hepcidin binds to an iron exporter ferroportin expressing on the basolateral membrane of enterocytes and induces the internalization and degradation of ferroportin, leading to a decrease in intestinal iron absorption. Various stimuli such as body iron stores, inflammation, erythropoiesis, and hypoxia affect hepcidin expression through the transcriptional regulation. This mini-review summarizes current understandings on the factors affecting hepcidin expression.