@mlwh if transvaginal estradiol improves bones, then it is not staying local, which was what my question was.

This is relevant for me because I had breast cancer.

That study is from 2007 and doesn't seem to provide much information on the delivery system or subjects unless I'm missing it or there is more detailed info elsewhere. There are too many confounders that are not disclosed to really rely on this study as being definitive (unless there is more complete data from this study elsewhere). Were none of them taking vitamin D or calcium prior to the study and therefore it had a positive impact? Were any of them exercising? Weight training? What was their diet? And most specifically, what is the delivery system? I'm wondering if "transvaginal" provides the same results as "transdermal" vaginal estrogen. There are estrogen creams for the vagina which are more topical and supposedly not systemic and there are rings that are inserted into the vagina which I believe deliver a systemic dose. It doesn't seem like a very well designed study to make any definitive conclusions but maybe there are other studies that can confirm.