Endogenous TPO (eTPO) levels in health and disease: possible clues for therapeutic intervention.

The factor which is the primary regulator of megakaryocyte and platelet production has recently been identified as the ligand for the receptor Mpl. This discovery has resulted in substantial advances in our understanding of platelet homeostasis. The access to new experimental reagents has enabled studies of the endogenous circulating form of this ligand, endogenous thrombopoietin, in normal individuals and in patients with altered platelet numbers. The relationship of endogenous TPO in health and disease will be examined with consideration of the implications for successful therapeutic intervention with exogenous recombinant Mpl ligands in selected settings.