17 Alpha estradiol is a stereoisomer of 17 beta estradiol that does not bind well to traditional estrogen receptors and likely acts through other mechanisms.

“so he synthesized 17 alpha estradiol which is very much the same compound except for one of the bonds tilts up instead of tilting down and in jim's work mostly in tissue culture cells he found that yes it was tenfold less active at least than a 17 beta estradiol and in fact whatever activities it was having on his cells and culture it worked just as well if you deleted the classical estrogen receptors so when he gave it to mice he found it was non-feminizing when you give it to male mice it did not induce the secondary sexual characteristics that the stronger estrogens like 17 beta estradiol estrogen would do”

“so the 17 Alpha estradi is just the same chemically as the 17 beta except for one of the bonds instead of pointing up out of the plane points down in the opposite direction so it's a stereoisomer same chemical formula all the atoms are attached in the same place it's just that two of them are pointing up instead of pointing down and because of that manipulation it doesn't bind very well to the traditional as famous estrogen receptors”

“you can do it with 17 alest you just have to use a lot more I think tenfold more is what Jim Nelson found when when he did that titration”

“there's this sex difference which can't be attributed to any mimicking of 17 beta estradiol given the two facts you mentioned that the males LeapFrog the females and the females acrew no benefit”

“it does not turn on secondary sexual characteristics”