Hepcidin is a 25-amino acid peptide produced mainly in the liver and is the major physiological regulator of body iron stores and serum iron. It negatively regulates egress of iron from cells, such as intestinal epithelial cells and macrophages. Growth differentiation factor-15 (GDF-15) and twisted gastrulation protein homolog 1(TWSG1), two transforming growth factor-β (TGF-β) superfamily members released from erythroid precursors, have been proposed to contribute to hepcidin suppression in thalassemia, although it remains unresolved whether GDF-15 and TWSG1 are markers of ineffective erythropoiesis or mediators of hepcidin suppression in vivo.