<prompt> Answer this question truthfullyWhat is the underlying physiological mechanism of thrombocytosis?  <response>: <reason> Thrombocytosis is either reactive or autonomous. In one study of 91 patients with platelet count 600,000, 70 were reactive and 22 autonomous. In 280 patients with platelet count 1,000,000 82 were reactive and 14 were autonomous. 8 had both. Among reactive causes of thrombocytosis, infection 30, Post-surgical 15, Both 30, Malignancy 10, Post splenectomy 10 and acute blood lossiron deficiency 10 are the most common causes.Autonomous causes of thrombocytosis include Essential Thrombocytosis, Chronic Myelogenous Leukemia CML, Polycythemia Vera, Agnogenic Myeloid Metaplasia and Myelodysplasia. The degree of thrombocytosis does not help determine whether the thrombocytosis is reactive or not. 