This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nephrotic Syndrome, Subject name: Pathology
What is the cause of hypercoagulation in nephrotic syndrome: 
Select and explain. 
A. Loss of antithrombin III (AT III), B. Decreased fibrinogen, C. Decreased metabolism of vitamin K, D. Increase in Protein C
A: Loss of antithrombin III (AT III)
Answer: A: Loss of antithrombin III (AT III) 
Explanation: Thrombotic and thromboembolic complications are common in nephrotic syndrome due to loss of anticoagulant factor (e.g. antithrombin III, protein C and S) combined with increased platelet activation. Renal vein thrombosis is most often a consequence of this hypercoagulative state. There is also increased synthesis of fibrinogen in the liver.