Thrombopoietin

The term “thrombopoietin” was coined in 1958 to describe the growth factor in the body that causes platelet counts to rise, but only in 1994 was this hormone isolated and identified. In the years since the identification of TPO, the specific pathway that it stimulates to produce platelets has also been elucidated. Endogenous TPO drives the production of platelets via the TPO receptor (TPO-R) on progenitor cells and megakaryocytes. The liver produces TPO at a constant rate, unaffected by extrahepatic signals, such as platelet count or serum TPO levels. The circulating level of TPO is regulated primarily by the clearance of TPO bound to circulating platelets. Any TPO bound to platelets is cleared when platelets are destroyed.^20,21,23

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