Estrogen blockers, also known as Anti-Aromatase or Aromatase inhibitors, are useful for men who have an excess of estrogen or are taking prohormones. Estradiol is the primary type of estrogen that is active in men. It plays a vital role in keeping men’s joints and brains healthy. It also allows sperm to develop properly. When there is too much of this estrogen in a man's body this can cause issues like weight gain, prostate problems, etc. An estrogen blocker is a supplement that will stop excess estrogen from causing these issues.