Estrogen Does NOT Cause Breast Cancer: Debunking Common Myths About The Hormone

While the attempt to objectify the effects of hormone replacement therapy is admirable, inappropriate interpretations have resulted in unprecedented fear of "all things estrogen."
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It is very popular to vilify estrogen these days. The most obvious reason is the result of several sensationalized interpretations of the famous WHI (Women's Health Initiative) "Prempro" data first out in 2002. While the attempt to objectify the effects of post-menopausal hormone replacement therapy is highly admirable, confusion and inappropriate interpretations have resulted in unprecedented fear of "all things estrogen." This has created huge challenges for those of us who are interested in the wellness and education of women.

MYTH: "Estrogen causes breast cancer."

REALITY: The best data indicates that not only does estrogen not cause breast cancer; estrogen supplementation after menopause might have a slight protective effect.

Estrogen induces breast development in our species, so of course there is a strong relationship with breast disease and the hormone that regulates breast growth-- but balance is the key. Persistently high levels of estrogen, such as in the obese woman (or even in pregnancy) can promote growth of abnormal cells that might otherwise have been plucked out by the immune system. This is not causation, but facilitation after the fact. Stating that estrogen causes breast cancer is like saying fertilizer causes weeds. In a garden even weeds need some soil nutrients, and if these are completely removed, the weeds can't grow...but neither can the desired plants. The fact is the positive metabolic effects of ideal amounts of estrogen may help the body defend itself from breast cancer before it starts.

MYTH: "If you are deficient in estrogen, taking bioidentical estrogen is safe."

REALITY: Bioidentical or not, estrogen does have risks.

Estrogen is Nature's gift to incite feminine differentiation. It is also loaded with a few bells and whistles to help protect some feminine liabilities. Women have a very unique reproductive cycle that results in more blood loss than any species on Earth. Menstruation is not unique to humans, but the amount of blood loss is. Surgery residents are known to gasp at the amount of blood lost during a routine C-section (when they are invited to observe), yet the pregnant woman clots like no advantage, and a risk. This tendency to lose enormous amounts of blood with reproduction probably explains why estrogen receptors in the human have evolved to increase clotting in the presence of the hormone. In other words: bioidentical or not, estrogen increases blood clot formation, and that may increase the risk of deep clots, pulmonary embolism (blood clots in the lung), and stroke. The good news: lifestyle factors and careful dosing can significantly modify these risks.

MYTH: "Estrogen makes you gain weight."

REALITY: Estrogen makes carbohydrate metabolism more efficient, helping to create the attractive waistline so closely associated with the fertile woman.

How many chubby-tummy little girls suddenly develop a carved out waistline by about age 15? Ask any menopausal woman if she feels skinnier without her estrogen? The truth is that estrogen has a very positive effect on metabolism, increasing the body's sensitivity to insulin, helping promote a smaller waist-to-hip ratio. It's easy to understand that features we humans see as "attractive" usually reflect fertility. In fact the best current data about metabolism and hormone replacement therapy in menopause demonstrates a positive effect for women taking HRT. The confusing factor is the association of estrogen with progesterone. Progesterone, the "other" female hormone, has its name because it it "pro-gestation." In other words, progesterone's job is to protect the assumed pregnancy, and that means pushing up blood sugar (hence the susceptibility to gestational diabetes), and weight gain with birth control high in progestins (synthetic progesterone). Progesterone also protects the uterine lining. Many of the effects associated with progesterone are mistakenly assumed to be due to estrogen. Most women feel their best when progesterone is not in the picture, during what I call the "Venus Week", the week after a woman's period.

MYTH: "Estrogen makes you stupid."

REALITY: Estrogen enhances verbal memory.

The scary part about the "stupid" myth is that everyone knows it's not true, but the converse is often only whispered about. My patients are horrified by the loss of verbal memory that often accompanies declining estrogen levels in menopause. I must admit it scares me to death, as my livelihood is deeply dependent on verbal skills. Many neurologists are now giving serious consideration to encouraging hormone replacement therapy for menopausal women who have a strong family history of Alzheimer's disease. Parkinson's disease (another potential cause of dementia) is far less common in women who take HRT, and while stroke risk complicates the risk/benefit profile, some women are very willing to take that risk to reduce their chances of verbal decline. To borrow a concept from Harvard gynecologist Dr. Alan Altman, it appears that estrogen is not a "repairer" per se, of verbal memory, but perhaps a preserver.

MYTH: "Men do fine without estrogen, so women don't really need it."

REALITY: Men actually do have estrogen, and have health consequences without it.

Men do not have ovaries, but they do have estrogen-- and the best evidence is that for the rare man that cannot convert testosterone to estrogen there are serious health consequences. A rare enzyme deficiency known as aromatase deficiency prevents a few men in the world from having any significant estrogen. These men not only have abnormal bone development, a high percentage suffer from what is known as metabolic syndrome, a deadly combination of high triglycerides, abdominal fat and elevated blood pressure. Cognitive effects are not well researched, but there is concern that even drugs that prevent the conversion of testosterone to estrogen (such as some used to prevent breast cancer recurrence in women) may have negative effects on the aging brain.

Ultimately we all must accept that nature endows us with estrogen as one way to promote reproductive vitality, it can't be all-bad. This gift has benefits and risks. Remaining "vital" is highly desirable, perhaps even negotiable, but fair negotiation is not possible if the stakes are not understood. There is still much unknown, but investigators are working hard as many are baby boomers on the brink of gonadal retirement themselves, whether they are men or women. One thing about baby boomers, we like being vital, so stay informed and stay posted.

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