How Does Estrogen Work?
As a messenger: During each menstrual cycle, estrogen together with other ovarian hormones signals cells in the breast to divide and multiply. Estrogen also signals the cells of the uterus to divide. How does estrogen make and deliver this “message” to divide? Other hormones signal the ovaries to make estrogen, and then the ovaries secrete estrogen into the bloodstream. Estrogen travels through the blood, but only the cells in estrogen target tissues, like the breast and uterus, can recognize and use estrogen because they have estrogen receptors. As a key in a lock: estrogen has a shape that allows it to fit into an estrogen receptor in the same way a key fits into a “lock.” The estrogen and the estrogen receptor bind to form a unit that enters the nucleus of the cell. The estrogen-receptor unit binds to specific regulatory sites on the cell’s DNA, and this begins a series of events that turns on estrogen-responsive genes. These specialized genes instruct the cell to make proteins that
