There is evidence that Milk Thistle is good at protecting the liver from toxins etc.
http://en.wikipedia.org/wiki/Milk_thistle#Amanita_mushroom_poisoning (http://en.wikipedia.org/wiki/Milk_thistle#Amanita_mushroom_poisoning)
Then It may cause the oral estrogen / progesterone not to pass or change them. This article mentions only the cleansing of the liver and the prevention of mushroom poisoning. Counterproductive. There are other methods to get HRT around the liver. The FDA does not approve of the herb for cancer chemo effects as well.
Joelene