How may smoking cause extra problems for people taking estrogen?

• A. Increases the risk of blood clots forming
• B. Decreases estrogen metabolism
• C. Improves vascular health
• D. Reduces risk of stroke

Answer: (A)

Smoking adds to the clotting risk that estrogen already poses. Estrogen therapy tends to increase clotting factors in the blood and can promote thrombosis. When someone who smokes also takes estrogen, smoking contributes to a prothrombotic state—along with possible vascular damage and platelet activation—so the chance that a blood clot forms goes up more-than-usually. This is the main way smoking creates extra problems for people on estrogen.

The other ideas don’t fit as well: smoking doesn’t improve vascular health, and while smoking can influence drug metabolism in some ways, the clinically important interaction here is the heightened risk of blood clots. Reducing stroke risk isn’t correct; in fact, estrogen users who smoke generally have higher cardiovascular and thrombotic risk.