We don't have high levels all the time, pre-menopause. At certain points in our cycle we might be at 800-1200, but then at other points it drops back to 50 or almost nothing. It isn't sustained at 800-1200.
And yes, probably it would be a lot harder to protect the endometrium if we were taking enough estrogen to keep levels that high. That is why we should only take enough to cope with symptoms and provide the health benefits.
Maybe one day they will come out with some HRT which mimics the natural cycle with changing levels of estrogen during the month. Although seeing what some of us go through when we change levels, maybe that isn't a good idea
I've no idea why our bodies are fine with such massive changes when it's our own hormones but not when we are taking the estrogen...
