@moxsom
I don't know what the exact mechanism would be -- perhaps methylation and/or histone modifications around key hair follicle development genes -- but there seems to be
some mechanism for permanent changes associated with things like development of facial hair and body hair. Perhaps A.G.A is analogous to that, or perhaps not...
So it would seem that, at least in the case of facial or body hair development, hormones may irreversibly change the regulated growth characteristics of hair follicles...? A.G.A may be similar, though it's not exactly symmetrical since A.G.A also causes damage to cells and so on. And as for the "switching mechanism", why would it have to affect all pathways?