This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Thrombopoietin is produced by- 
Select and explain. 
A. Monocytes, B. Liver, C. Megakaryocytes, D. Megakaryoblasts
B: Liver
Answer: B: Liver 
Explanation: *Thrombopoietin is present in the blood as well as in a bound state with the platelets. It also binds with the megakaryocytes. It is produced by the liver and the kidneys. * When thrombocytopenia (reduction in platelet count) occurs, thrombopoietin level in blood rises. This helps the megakaryocytes in producing new platelets rapidly.