American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What is the primary reason for decreased synthesis of clotting factors?

1. Vitamin K deficiency

2. Vitamin D deficiency

3. Vitamin A deficiency

4. Vitamin E deficiency

The correct answer is: Vitamin K deficiency

The primary reason for decreased synthesis of clotting factors is vitamin K deficiency. Vitamin K plays a crucial role in the post-translational modification of certain clotting factors, specifically factors II (prothrombin), VII, IX, and X. These factors require vitamin K to undergo a process known as gamma-carboxylation, which is essential for their normal function in the coagulation cascade. Without adequate vitamin K, the liver cannot synthesize functional clotting factors, leading to increased bleeding risk and prolonged coagulation times, as seen in conditions such as vitamin K deficiency. In contrast, vitamin D, vitamin A, and vitamin E deficiencies are not directly involved in the production or activation of clotting factors. Vitamin D primarily regulates calcium and phosphorus metabolism, vitamin A is vital for vision and immune function, and vitamin E acts as an antioxidant. While deficiencies in these vitamins can lead to other health issues, they do not directly compromise the synthesis of clotting factors in the way that vitamin K deficiency does.