Studies in cismen with advanced prostate cancer (risk is increased due to age and cancer), aged 49-91 yrs old, have shown that high estradiol levels (mean, 500-600 pg/ml, up to around 1,000), taken transdermally, did not lead to increased cardiovascular or thromboembolic complications. There was actually normalization of clotting.
In women with advanced breast cancer and aged 40-92 yrs old, despite VERY high doses of oral bio-identical estradiol and levels of estradiol around 2,500 pg/ml, there was only one incidence of thrombosis in more than 50 women, follow-up 6-22 months.
Food for thought...