Thombopoietin is the recently discovered glycoprotein hormone that regulates the production of platelets. Before its identification, its function has been hypothesized for as much as 30 years as being linked to the cell surface receptor c-mpl, and in older publications thrombopoietin is described as c-mpl ligand (the agent that binds to the c-mpl molecule).

Function and regulation

Thombopoietin regulates the differentiation of megakaryocytes and platelets. Its negative feedback is different from most hormones in endocrinology: the effector regulates the hormone directly. Thrombopoeitin is bound to the surface of platelets, thereby reducing megakaryocyte exposure to the hormone.

Genetics

The thrombopoietin gene is located on the long arm of chromosome 3 (q26.3-27). Abnormalities in this gene occur in some hereditary forms of thrombocytosis (high platelet count) and in some cases of leukemia.