Hop extract exerts local estrogenic activities when applied topically.  The active substance 8-PN (8-prenylnaringenin), responsible for the estrogenic effect in hops, was identified in 1999 by Milligan.  Phytoestrogens in the body act like weak estrogens and, when applied topically, will not impact the overall hormonal balance.  Estrogens profoundly alter hair growth by binding to estrogen receptors in the hair follicle.  Besides altering estrogen-dependent genes, estrogen modifies hair follicle metabolism in the hair follicle and the sebaceous gland.