Hormones are natural substances made by glands in our bodies. The network of glands that make hormones is called the endocrine system. Hormones are carried in our bloodstream and act as messengers between one part of our body and another. They have lots of effects and one of these is controlling the growth and activity of certain cells and organs.Some cancers use these hormones to grow. Hormone therapy for cancer is the use of medicines to block the effects of hormones Hormone therapy is another form of systemic therapy. It is most often used as an adjuvant therapy to help reduce the risk of the cancer coming back after surgery, but It is also used to treat cancer that has come back after treatment or has spread. Use of Hormones in breast & prostate cancer is quite effective.Some breast cancer cells need estrogen and/or progesterone (female hormones that are produced in the body) to grow. When these hormones attach to special proteins called hormone receptors, the cancer cells with these receptors grow.Hormone therapies slow or stop the growth of hormone receptor-positive tumors by preventing the cancer cells from getting the hormones they need to grow.