In the healthy woman, estrogen and progesterone (the two primary female reproductive hormones) exist in balance with one another.  Estrogen dominance occurs when estrogen is not balanced in the body with enough progesterone.  In this case there might be too much estrogen, too little progesterone, or both.  There are many different health scenarios that may lead to this imbalance.  Further, estrogen dominance is often closely associated with poor estrogen processing, which only adds to the problems and risks associated with estrogen dominance.