Effect of hyperthyroidism on hypoprothrombinemic response to warfarin.

Clinical observations and studies regarding hyperthyroidism and enhanced response to warfarin are reviewed. The reported cases of increased sensitivity to warfarin in hyperthyroidism are summarized, and possible mechanisms for this disease-drug interaction are discussed. Most recent studies indicate that the activity of warfarin is enhanced in hyperthyroidism because of increased catabolism of vitamin-K-dependent clotting factors.