In my post I said there are no data of estradiol effect at microM concentration in vitro, so mentioned the closest possible study testing a dose response from nanoM to microM. MicroM estradiol doesn't happen in nature on hair follicle, but can happen by putting at 0.05% topical on the scalp.Estrogen does not cause hair loss in humans and is hair protective. The study you linked is on epithelal lens cells, which have entirely different morphology than hair follicles. For example, estrogen causes proliferation in mammary cells but causes apoptosis in prostate cells. I have yet to read the first study that demonstrates a catagenic effect of E2 in human hair follicles. There have been reports of the anagen promoting effect of E2 being dependent on the scalp region in absence of androgens. In presence of androgens, E2 induces AR downregulation and thus makes androgens less "effective" (this is actually becoming a big problem for males with all traces of birth control pills floating around in tap water).
If the scope is to make working best estradiol on hair follicle, then I assume the target concentration has to be nanoM, as microM is orders of magnitude above the physiological concentration. I think you are the only one that is testing estradiol a very low dosage, on 5ARi and topical AA and I believe your test is very interesting, as I couldn't find a true microdosing test for topical estradiol.