Estrogen is a female hormone related to childbearing. For this reason, it is most active in the breasts and uterus. In turn, the tissues in the beast and uterus are very sensitive to the presence of estrogen. Estrogen prepares the body of an adult woman for pregnancy, which it does by promoting cell proliferation in the lobules and ducts of the breast – a precursor to milk production – and in the uterine lining or endometrium.
During the menstrual cycle, estrogen levels rise following ovulation, but if no fertilized egg gets implanted in the uterus, the amount of estrogen falls sharply and menstruation takes place.
Birth Control The Pill & Breast Cancer Risk
Estrogen cannot be said to cause cancer. However, estrogen’s prime function is to speed up the process of cell proliferation. It may also encourage the growth of cancerous cells once they appear. The more estrogen a woman is exposed to in her lifetime, the greater the chances that estrogen will have the opportunity to promote the growth of a tumor.
This is why personal history risk factors are so important. A woman who starts menstruating early or goes through menopause late has a longer lifetime exposure to estrogen. A woman who has not gone through childbirth or breastfeeding, both of which tend to suppress the menstrual cycle for extended periods of time, does not get the risk-lowering benefit of these events.
It is well-known nowadays that the greater a woman’s exposure to estrogen, the greater her risk of developing breast cancer.
Breast cancer survivors who took hormone replacement therapy (HRT) to relieve menopausal symptoms had more than three times as many recurrences as survivors who did not take HRT.
It is therefore recommended that women discuss with their doctors whether the benefits of taking estrogen outweigh the risks and that, if used, the hormones should be taken at the lowest doses for the shortest duration to reach their treatment goals.
What is the effect of oral contraceptives
There are two other potential sources of exposure to estrogen – xenoestrogens and phytoestrogens. Xenoestrogens are chemical compounds that have similar effects in the body as estrogen. They are generally related to pesticides and industrial products, such as DDT and PCBs. The exposure to these synthetic hormone-activating agents may increase the risk of contracting breast cancer and other cancers of the reproductive tissue.
Phytoestrogens are natural, estrogen-like compounds, or hormone active agents (HAAs), in plant foods, such as whole grains, seeds, fruits, and, particularly, soybeans. Although these HAAs have estrogenic activity, it is between 1/30 to 1/1000 as powerful as natural estrogen.
It is thought that this low estrogenic activity makes it protective against breast cancer. A diet high in soy-based phytoestrogens may explain the relatively lower rates of breast cancer among Asian women.