Hi,
I have had such high levels of estradiol when checking hormones while on HRT., but only once. Normally my levels will be 300-600 on day 3 of menstrual cycle. My gynae has always said that measuring levels of progesterone and estradiol is useless while on HRT, more important is to look at measures/levels of FSH for example. My last FSH measure was about 7-8. He thinks this indicates I do well on the therapy. Because your FSH was pretty high before starting HRT, and has subsequently fallen, this means the therapy is effective . Why estradiol is so high ? - probably you've had a surge of your own hormones in addition to the HRT. I am not sure here.
Is there a reason why you are on estrogen-only HRT?
Milamam