Thrombopoietin (TPO) is a glycoprotein hormone primarily produced by the liver and kidney. It plays a crucial role in the regulation of platelet production by stimulating the maturation and proliferation of megakaryocytes, the bone marrow cells responsible for the production of platelets. TPO achieves this by binding to its receptor, c-Mpl, on the surface of megakaryocytes and their progenitors.