SERUM THROMBOPOIETIN LEVEL IS MAINLY REGULATED BY MEGAKARYOCYTE MASS RATHER THAN PLATELET MASS IN HUMAN-SUBJECTS

A patient with idiopathic thrombocytopenic purpura (ITP) developed T-c ell lymphoma while undergoing steroid therapy. We examined the relatio nship between the patient's serum thrombopoietin (Tpo) level, platelet count, megakaryocyte number and CPU-Meg number during the second 5 d course of chemotherapy for lymphoma in which megakaryopoiesis switched from ITP phase to amegakaryocytic phase. The patient's platelet count was temporarily elevated but CPU-Meg numbers were markedly suppressed , and megakaryocyte numbers were decreased in this period, whereas ser um Tpo level was not suppressed despite an increased platelet count, i ndicating that serum Tpo level is mainly regulated by megakaryocyte ma ss.