https://www.ncbi.nlm.nih.gov/pubmed/3569146
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Cells treated with 2.6 nM estradiol exhibited markedly lower levels of cytoplasmic androgen receptors, measured by [3H]5 alpha-dihydrotestosterone ([3H]DHT) binding, compared to levels in cells receiving ethanol vehicle alone. The effect was time dependent, and 6-day treatment of cells with estradiol resulted in an 80% reduction in [3H]DHT binding.
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In summary, estradiol treatment caused a reduction in androgen receptors, and estradiol withdrawal lead to a rise in androgen receptors. We believe that these results provide a mechanism whereby estradiol may directly antagonize androgen action. Conversely, estradiol withdrawal may potentiate androgen action by allowing androgen receptor levels to rise."
This clearly explains why those using estradiol experience such incredible regrowth. 2.6 nM of estradiol resulted in a 80% reduction of AR binding of DHT and a 50% reduction in AR levels.
So not only does estradiol cause activation of the ER which causes estrogenic gene expression taking your cells in the opposite direction of hair loss but it also downregulates the presence of the androgen receptor.
Anti androgens like Bica, Daro, and RU etc increase androgen receptor sensitivity so the smallest topical amounts of estradiol along with AAs could produce huge benefits
Any of you with very aggressive forms of hairloss may want to experriment by combining your 5AR inhibitior with topical estradiol and a topical AA. The dosage you pick is crucial as estradiol is a very potent hormone, I would say start with 25 micrograms and adjust your dose from there. Do NOT use estradiol without an anti-estrogen like Raloxifene or Tamoxifen on hand.