Regulation of LH production (or actually both of LHRH – LH releasing hormone – and the pituitary’s responsiveness to LHRH) is a function not only of androgen levels, but also estrogenic activity in those organs, as well as a number of other factors.
Unfortunately it turns out that while I recycled (in much expanded form) most of the articles I’d written for Dan Duchaine’s newsletter when working for him, I forgot to ever recycle the one on LH regulation.
Unfortunate, because I researched that one a lot, it is quite complicated, and frankly I forget most of the details. And the old newsletters aren’t available online unless one pays for them, which I’m not going to do, and I’m far too disorganized to still have a copy.
So rather than give a full explanation, which I know from experience would take a long time to get the details right, briefly these SERMs reduce the degree of partial estrogenic inhibition that is normally present even with fairly low estrogen, and even more interestingly as they have mixed activity there is a respect in which estrogen increases LH production in which they conveniently act like estrogen, instead of blocking estrogenic effect.
So you get the positives of estrogen with regard to LH production but not the degree of partial inhibition that is normally always present. Or at least, that is greatly reduced.