The connection between hormones and breast cancer is not fully understood, but is based on studies and research that link estrogen, progesterone, and similar synthetic compounds to breast cancer rates. With the advent of hormone replacement therapy (HRT) used for women whose bodies lack the ability to produce adequate amounts of these hormones, cancer researchers have been able to establish the existence of a significant relationship between an overabundance or lack of effective transmutation of these hormones and a woman’s risk of developing the disease. Estrogen is most often implicated in the link between hormones and breast cancer because this hormone possesses some characteristics that can lead to the unrestricted cell growth seen in the disease. Estrogen is the hormone that stimulates breast cells to divide under normal periods of growth and development, and this fact seems to facilitate the hormone being prone to metabolic changes that lead to cancer cell proliferation.
Within the hormones and breast cancer research community, there is debate as to why older women are at a higher risk for breast cancer but have lower levels of both estrogen and progesterone. Some researchers point to this data irregularity as an argument that hormones and breast cancer have a weaker link than originally thought. Other researchers, however, see the data as a sign that a woman’s body is not meant to metabolize large amounts of these hormones after menopause and that when it is forced to do so, cancer may develop. The woman’s natural lifetime exposure to the hormones—which can include unintentional environmental exposure to estrogen-mimicking compounds—often times couples with HRT as she enters menopause and acts as a switch that causes cancer cell proliferation within the breast tissue.
While the drugs used in traditional HRT are not bioidentical to the estrogen and progesterone that the body produces, it has been shown in studies that the chemicals used to make their synthetic equivalents may activate the same receptor proteins in breast tissue, which may cause cancer. In regard to estrogen-mimicking compounds, there are many ways in which women can be exposed to these toxins, like the ones formed by the breakdown of certain types of plastics, in everyday life. These toxins contain the same steroid ring, which can then mimic estrogen activity in the body, often times causing havoc within the system and boosting blood levels of estrogen above the acceptable range. There are new hormone drugs on the horizon which address some of these issues and are showing promise as being safer for HRT.