Therapy that introduces synthetic A hormone that stimulates the uterus to prepare for pregnancy, produced mainly by the ovaries. Progesterone may play a role in certain breast cancers. and A female sex hormone that is primarily produced by the ovaries. Its primary function is to regulate the menstrual cycle and assist in the production of secondary sex characteristics such as breasts. It may even play a role in the production of cancer cells in the breast tissue. into the body after it has stopped making its own because of natural or induced The end of a woman’s menstrual cycles, defined as 12 consecutive months of no menstrual periods.. HRT relieves the symptoms of menopause, but may also increase risks for developing breast cancer.