BY: Kiaora Staff | Last Updated: October 12, 2024 | Medically Reviewed By: Dr. Kay Chandler OBGYN/ FACOG
In the early 2000s, women's health care faced a seismic shift that continues to reverberate today. Millions of women abruptly stopped hormone therapy for menopausal symptoms, alarmed by headlines warning of increased risks of breast cancer and heart disease. This mass exodus wasn’t just a personal choice for many—it signaled a public health crisis.
At the heart of this crisis was a single study: the Women’s Health Initiative (WHI), whose 2002 results were heralded with the drama of a blockbuster movie premiere. The message was clear and alarming: hormone therapy was dangerous for women.
But here's the twist—this message was deeply flawed.
The WHI study, which ignited widespread fear of hormones and cancer, actually found no increased risk of breast cancer in women who used estrogen-only hormone replacement therapy (HRT). In fact, it suggested a reduced risk. Dr. Lindsey Berkson, in her book Estrogen Vindicated, points out:
"The women who took horse-derived estrogen without synthetic progestins experienced a decrease in breast cancer risk. Over 7.1 years, breast cancer reduction ranged from 18% to 44%, depending on the analysis. Specifically, localized breast cancer dropped by 31%, and ductal breast cancer by 29%."
"Even ten years later, this reduced risk persisted, even with less than six years of estrogen use. The benefit now appears to last for up to 19 years."
You may have heard of women choosing to have double mastectomies due to the BRCA1 gene mutation, which raises lifetime cancer risks. In a 2008 study from the Journal of the National Cancer Institute, researchers followed 472 postmenopausal women with the BRCA1 gene. Half of the women were on hormone therapy, while the other half were not. The conclusion was striking:
“For postmenopausal women with a BRCA1 mutation, estrogen use for about four years was not linked to a higher risk of breast cancer—in fact, it was tied to a noticeable reduction in risk.”
And it’s not just women with the BRCA1 mutation. A study tracking 10 million women over 65 found that those using bioidentical hormones had consistently lower breast cancer rates compared to those not using hormones.
So, how did estrogen become linked to breast cancer in the first place? Let’s revisit the WHI study. In 2002, the WHI—after costing around $260 million—was suddenly halted. Headlines claimed an increased risk of breast cancer and stroke, causing widespread panic. Women worldwide stopped using HRT, and doctors became hesitant to prescribe it. Hormone therapy prescriptions plummeted by 70%, while antidepressants, osteoporosis drugs, and anxiety medications surged—a trend that persists today.
The fear of estrogen has lingered ever since. Many women remain apprehensive, and even today, countless doctors advise against its use. As a result, peri- and postmenopausal women often find themselves without hormonal support due to widespread misinformation.
Once the initial panic from the WHI study subsided, a clearer picture emerged: estrogen itself wasn’t the problem—the real culprit was synthetic progestin. The women in the study who used estrogen alone did not experience an increased risk of breast cancer. In fact, they saw a reduced risk. However, the group taking both estrogen and progestin (Prempro) experienced a slight increase in breast cancer, stroke, and heart disease. This increase was so marginal it barely reached statistical significance.
The WHI also showed that women who began estrogen therapy before age 60 saw a 35% lower mortality rate compared to those who didn’t use hormones. Unfortunately, these findings were buried beneath alarming cancer headlines.
By 2003, WHI researchers revisited their data and acknowledged that the risks—especially those tied to Prempro—were lower than initially reported. However, this clarification did not capture media attention. By 2006, further analysis showed there was no significant increased risk of breast cancer for women taking both estrogen and progestin, but this important update went largely unnoticed.
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It is estimated that the reduction of estrogen hormone therapy between 2002 and 2011 in hysterectomized women aged 50 to 59 years resulted in an in all-cause mortality increase of 18,601 - 91,610. (American Journal of Public Health).
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