We have a lady on here that is the Hormone Queen hope she will see this and answer you soon
Afraid I am not the hormone queen, but I had been on ERT for some 12 yrs after a total hysterectomy, when I was dx with bc in 2003. My breast surgeon strongly advised me to stop taking ERT, which I did. My bc was hormone positive, so although I do get hot flashes, during the day and worse at night, I just daren't go back onto it. I think the jury is still out on whether ERT can cause bc, and there are also conflicting reports on whether or not ERT can help prevent heart attacks and strokes. Have you thought of posting your question on the "Ask The Nurse" part of this site? She is very knowledgeable and may be able to answer your questions about ERT causing cysts.
Take care,Liz.