Read: Silymarin's effect on LH, Estradiol, Testosterone, etc. - Confusing though

http://egyptianjournal.net78.net/13_10.pdf

Apparenty Silymarin is an aromatase inhibitor, but has "a definite estrogenic effect", and prevents preganancy in female rats.

From the link above:
"In male rats ,a significant increase of
serum testosterone and LH levels while
estradiol did not change by silymarin
treatment at one month.  Oliveira  et al.,
(2001) "


"While rats treated with silymarin for
two months displayed significant decrease
in serum testosterone levels, while LH and
estradiol not changed. This result is
attributed to enzyme regulation for
testosterone synthesis which may be
affected by phytoestrogen rich diet and
decreased  testosterone levels Weber et al.,
(2001)."