In studies where men, between the ages of 49-91 yrs old, had advanced prostate cancer and thus were more likely to have a thrombosis, the administration of bio-identical estradiol in the form of patches actually reduced a few clotting markers including fibrinogen, D-Dimer and F1+F2 while others remained normal, despite estradiol levels as high as 1,000 pg/ml.
In another study where a few transsexual women had an inherent predisposition to increased clotting, the administration of estradiol in the form of patches did not result in any incidence of thromboembolism.