I am concerned that the specific points made by the authors about protein C and factor VII provide an oversimplistic and somewhat inaccurate interpretation of the available data. First, Grady and colleagues postulated that the higher levels of protein C seen with the use of estrogen may be thrombogenic. Second, Grady and colleagues speculated that an effect of estrogen to increase factor VII levels may have thrombogenic effects. However, once again it is the effect of combined HRT on factor VII that is more relevant.
More study is required to determine the mechanisms underlying such increases.
Roger Peverill, MB, BS, PhD Monash Medical Centre and Monash University Clayton 3168, Australia References 1. Grady D, Wenger NK, Herrington D, Khan S, Furberg C, Hunninghake D, et al. Postmenopausal hormone therapy increases risk for venous thromboembolic disease. Ann Intern Med. The Atherosclerosis Risk in Communities Study Investigators.