Question

Hypercoagulation in nephrotic syndrome is caused by:

• A. Loss of antithrombin III
• B. Decreased fibrinogen
• C. Decreased metabolism of vitamin K
• D. Increase in protein C

Hint:

An anticoagulant similar in size to albumin slips into the urine.

Answer 1

The Correct Option is A

Step 1: In nephrotic syndrome the glomerular filter leaks protein, so the urine loses large amounts of plasma proteins. The pattern of which proteins are lost and which rise explains the clinical complications.
Step 2: Antithrombin III is a small natural anticoagulant of similar molecular size to albumin, so it is lost in the urine. Falling antithrombin III removes a key brake on coagulation and tips the balance towards clotting.
Step 3: At the same time the liver increases synthesis of large clotting proteins such as fibrinogen, and there is increased platelet activity, all of which further promote thrombosis (for example renal vein thrombosis).
Step 4: Why the others are wrong. Fibrinogen is increased, not decreased, in nephrotic syndrome, so option B is the opposite of the truth. Vitamin K metabolism is not the driving abnormality. Protein C is an anticoagulant, so an increase would reduce clotting rather than cause hypercoagulability, making option D the reverse of what happens.
Step 5: The main cause of the hypercoagulable state is therefore urinary loss of antithrombin III.
Answer: Option A (Loss of antithrombin III).