A brief summary of when hormone therapy will or won't work. There's both a video and a transcript of the video. There's not much explanation about the link between hormones and breast cancer. It's not fully understood, but estrogen is thought to stimulate breast cell division and to interact with other hormones/molecules that also stimulate breast cell division. Some studies indicate that women with a higher lifetime exposure to estrogen may be at great risk for breast cancer. In clinical trials, antibodies that bind to the estrogen receptor (blocking it from binding to estrogen) have been found to be effective in treating certain kinds of breast cancer (as the video explained, breast cancer where the cancer cells are positive for the expression of these proteins). Progesterone on the other hand seems to inhibit breast cell division.