Interestingly, I also came across this...
Br J Obstet Gynaecol. 1990 Oct;97(10):917-21.
"Increased levels of oestradiol may be beneficial, not only for their anti-depressant effect, but also in their effect upon bone density. The latter is greater after implant therapy than after oral therapy and is related to the greater plasma oestradiol levels achieved in women with implants. None of the 38 patients complained of alleged symptoms 01 oestrogen excess, such as breast tenderness, fluid retention or nausea."
"The mean serum oestradiol level of the 1388 women attending the clinic in 1988 was 767 pmol/l (range 78-2925 pmol/l), 66% had serum oestradiol levels <1000 pmol/l and 3% (38 women) had levels >1750 pmol/l (Fig 1)."