Response of blood coagulation parameters to elevated endogenous 17β-estradiol levels induced by human menopausal gonadotropins

To elucidate the relationship between estrogen and thrombosis, we studied blood coagulation parameters in women whose ovaries were stimulated with human menopausal gonadotropins (hMG). Daily hMG administration over 1 to 2 weeks in seven anovulatory women increased plasma 17β-estradiol levels fivefold over the pretreatment value. Of the coagulation parameters, the fibrinogen level increased significantly from an initial value of 248 ± 11.7 mg/dl (mean ± SEM) to 353 ± 32.2 mg/dl after hMG treatment (P < 0.05), with a significant positive correlation between estrogen and fibrinogen levels (r = +0.762). In addition, a thrombokinetics study showed that the maximal rate of change in optical density of the prothrombin time and activated partial thromboplastin time was significantly increased, suggesting that the coagulation factors involved in extrinsic, intrinsic, and common pathways could be increased by estrogen. Antithrombin III levels decreased gradually during hMG administration. Thus, increased endogenous estrogen levels appear to induce the so-called “hypercoagulable state” through both an increase in coagulation factors in the coagulation cascade system and a decrease in antithrombin III, a potent natural inhibitor of activated coagulation factors. Patients on a regimen of hMG treatment for induction of ovulation serve as excellent models for the study of alteration of “natural” estrogen-mediated coagulation parameters.