I just wanted to chime in and say almost all studys on HRT. are from Ethyl Estradiol. a type of Pharmaceutical Estrogen, not used in HRT Treatment due to its high costs and extreme damage it does to the cardiovascular system. 

It's used by researchers because pharmacutical recommendations(they have still yet to recover the losses from there research, several decades ago)

Ethyl Estradiol, is one of MANY types of estradiol. the risks involved in its usage is EXTREMELY high by comprison to Estradiol Valerate or Estradiol Benzoyl. Check the HRT chart for more information.