Thrombopoietin (TPO) is a growth factor that is produced by the liver and kidney. TPO acts through the TPO receptor to promote megakaryocyte matu ion and differentiation, which leads to the production of platelets. Recombinant TPO is a non-glycosylated Protein, containing 174 amino acids (which comprise the receptor binding domain), with a molecular weight of 18.7 kDa.