Causes of Breast Cancer? Risk Factors that May Affect Hormones

Phyllis Johnson Health Guide
  • Breast cancer occurs when the DNA in a breast tissue cell is damaged, and the cell reproduces too rapidly.  But what causes this DNA damage?  Scientists are still researching to find the answer, so no one truly understands the causes of breast cancer.  We do know that exposure to estrogen can be a factor in who gets breast cancer.

    As I explained in an earlier article, risk factors are not the same as causes.  They are conditions that are known to be more common in people who get breast cancer.  Because many women who have breast cancer have no known risk factors and women who have several risk factors may never develop breast cancer, a risk factor is not a cause.  Nevertheless, scientists have noticed that many of the risk factors for breast cancer are related to estrogen exposure and hormone regulation.  Some of these risk factors are not easily controlled by choice.  These include early age for first menstruation, no childbirth, childbirth after age 30, and late age for menopause.

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    However, there are other factors that affect hormones that may have a connection to breast cancer.  Some are definitely connected, and some are still under study or controversial.  Here are some possible risk factors that you can control.


    Hormone Replacement Therapy (HRT)  Many women have used estrogen or estrogen/progesterone pills to relieve menopausal symptoms.  In fact, at one time HRT was believed to reduce a woman's risk of heart disease and other problems of aging.  Then in 2002, a large study by the Woman's Health Initiative was stopped because it turned out that the group of women receiving HRT had a higher rate of breast cancer and no benefits to heart health.  Subsequent studies have confirmed these original findings.


    Although some people argue that today's HRT uses smaller doses of hormones than earlier versions, it makes sense that any hormone strong enough to reduce menopausal symptoms might also be raising the risk of breast cancer.  Women who have early medical menopause and those who have severe hot flashes or other troublesome menopausal symptoms should discuss with their doctors how much risk they would incur by taking HRT and then decide the best balance of risk and benefits for them.


    Birth control pills: Birth control pill users may have a slightly higher risk of breast cancer, but studies into birth control pills and cancer are contradictory-perhaps because there are so many different formulations of the pill.  After stopping birth control pills, the risk decreases over time and by 10 years after stopping the pills, users and non-users have the same risk.  A woman who has other risk factors for breast cancer will want to discuss with her doctor whether birth control pills are right for her.  Because pregnancy has its own set of health risks, the pill may still be the best option for many women, especially for young women who are at low risk for breast cancer because of their age.


    Alcohol use.  Another substance with connections to breast cancer is alcohol.  Research led by the National Cancer Institute's Jasmine Lew in 2008 found that women who had one to two small drinks a day were 32 percent more likely to get hormone-sensitive breast cancer. Three or more drinks a day increased the risk by 51 per cent.  The research focused on post-menopausal women, and the researchers theorize that alcohol affects the way the body metabolizes estrogen.  Because there are studies showing that moderate amounts of alcohol may improve heart health, it would be a good idea to discuss with your doctor whether small amounts of alcohol would be appropriate for you.


    Chemicals.  Many people suspect that chemicals in pesticides, plastics, and the myriad of other products we use in modern life may cause cancer by affecting estrogen levels.  So far, studies are inconclusive perhaps because there are so many substances that may interact in so many different ways in our bodies.  Most of the studies showing problems with pesticides and plastics have been done on animals, and results in animal studies do not always translate to the same results in humans. 

    How can you function in society and find a reasonable response to the possible risk of chemical exposure?  Read labels and choose foods and skin care products with the fewest artificial ingredients and preservatives.  Look for meats and milk from animals that were not fed antibiotics or hormones.  Be careful around chemical products you use to clean your home by providing good ventilation and washing your hands thoroughly.  These precautions are especially important for your daughters because most mutations that lead to breast cancer are believed to start years before the cancer grows large enough to be discovered. 

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    At the same time, keep the risk in perspective.  According to Dr. Susan M. Love, "Several observational studies have failed to demonstrate a relationship between occupational exposure to pesticides and breast cancer."  She concludes that there may be a connection between the chemicals in our environment and breast cancer, but that the risk is probably small.


    Weight.  The strongest connection between being overweight and getting breast cancer is in post-menopausal women.  Although the exact connection is not completely understood, scientists theorize that because fat cells store estrogen, being overweight after menopause provides more estrogen to feed growing cancer cells.  Some people think that a high-fat diet or a sedentary lifestyle may be the culprits rather than the weight itself, but again studies are inconclusive as to the exact connection.  

    According to the American Cancer Society women who have gained 55 pounds or more since age 18, are 1 1/2 times more likely to get breast cancer than those women who've maintained their weight. Those who gained 22 pounds or more after menopause, have an almost 20% greater risk of getting breast cancer than those women who maintain their pre-menopause weight.  We know that a low-fat diet rich in fruits and vegetables improves health in many ways, so even if there is no proven connection to breast cancer prevention, it makes sense to eat a healthy diet and control our weight.


    Smoking.  A study released in January 2011 found a connection between pre-menopausal smoking and breast cancer after looking at data from the Nurses' Health Study, which included the medical records of 111,140 active smoking females from 1976-2006.  The researchers found a link between current or past smoking and breast cancer risk. If the woman smoked for longer, started at an early age, and consumed more cigarettes per day, her breast cancer risk was higher.  Interestingly enough, women who smoked after menopause had a slightly decreased incidence of breast cancer, and once again estrogen seemed to be a factor.  The researchers found that ingredients in cigarette smoke decreased the estrogen in the post-menopausal women.


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    These are some of the habits that affect hormone levels in women and that may be related to breast cancer.  There are other risk factors for breast cancer, but many of them are conditions that you cannot control.  If you are worried about getting breast cancer, why not develop a life style that reduces your risk where you can?  We do not have to know exactly what causes breast cancer to live in a healthy way.




Published On: July 08, 2011