does estrogen cause cancer in women?
This is not causation, but facilitation after the fact. Stating that estrogen causes breast cancer is like saying fertilizer causes weeds. In a garden even weeds need some soil nutrients, and if these are completely removed, the weeds can't grow...but neither can the desired plants.
One of the most significant questions raised by the new study is what, if any, effect the striking rise in estrogen has on a woman's risk of breast cancer. Studies show that estrogen therapy protects against heart disease and osteoporosis but may increase the risk of breast cancer. Some research also shows that moderate alcohol consumption -- one drink a day for a woman -- may decrease the risk of heart disease and increase the risk of breast cancer, as well.