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HRT and the mystery of Marin County

April 6, 2011
By Mary Lou Williams, M. Ed.

Marin County, located just over the Golden Gate Bridge from San Francisco, is the most uniformly white, affluent, and well-educated county in California, and perhaps the country. It also has one of the highest rates of breast cancer in the world. Why do so many women in Marin County get breast cancer?

Uterine Cancer And Estrogen

The story begins in 1975. As chief of the California cancer registry, Donald Austin directed one of the largest storehouses of local cancer statistics in the world. Researchers frequently consulted him about the incidence of the disease in the San Francisco area. When asked in 1975 for a tally of all cases of breast, uterine and ovarian cancer in the registry, Austin was startled by what he found. Since 1969, uterine cancer in the Bay Area had risen by 50 percent. The incidence among women age 50 and over from affluent Marin County had doubled.

It didn't take long to finger the culprit. Prescriptions of estrogen, the hormone used to treat symptoms of menopause, had tripled nationwide between 1965 and 1975, mostly to affluent women over 50. Estrogen use plummeted after 1975, when studies revealed that women taking the hormone had up to a 14-fold increased risk of uterine cancer. Medical sleuths eliminated the risk of uterine cancer by adding synthetic progesterone (progestin) to the estrogen prescription, thus the change of name to hormone replacement therapy or HRT. While estrogen prompts the uterine lining to thicken, progestin signals it to stop growing and slough off; this artificial menstrual cycle seems to prevent endometrial cancer.

Within three years, the rate of uterine cancer returned to normal. And the rate of prescriptions for HRT surged as a raft of studies (observational studies, not clinical trials) showed new and unexpected benefits - increased longevity, protection from heart disease, osteoporosis, Alzheimer's disease. As of July 2002, 13 million American women were on hormone-replacement therapy, making it a billion-dollar business.

Breast Cancer And Hormone Replacement Therapy

In 1960, a woman's chance of developing breast cancer during her lifetime was 1 in 20. In the 1970s, it was 1 in 11. In the 1980s, it went up to 1 in 10. In the early 1990s, it was 1 woman in 9. In 1999, it was 1 out of 8. In Marin County the rate has been skyrocketing, up 60 percent since 1991. Marin County women between the ages of 45 and 64 are especially vulnerable; the likelihood of their being diagnosed is at least 72 percent higher than that of women the same age in the rest of California. Why? A clue can be found in the results of the Women's Health Initiative, a large, federally funded clinical trial on postmenopausal HRT, whose results were published in July 2002. Not only were the hormones estrogen and progestin not the age-defying wonder drugs everyone thought they were, but they caused an increase in heart disease, stroke, pulmonary embolisms (blood clots in the lungs), blood clots in the legs, and Alzheimer's disease.

And they caused a significant increase in breast cancer. It appears that estrogen plus progestin has a more negative effect on the breast than estrogen alone.

This last result is not news: a study reported on the front page of the New York Times of August 3, 1989, found that women who took estrogen alone had a breast cancer rate about double that of women who took no hormones. In women taking progestin as well as estrogen, the rate of breast cancer was four times as high as the rate among women who took no hormones at all. (The July 2002 study got much more attention because its findings on other diseases were unexpected.)

Affluent, professional women, such as the women of Marin County, are more likely to go on hormone replacement therapy at menopause than women on lower rungs of the socioeconomic ladder. Although they have other lifestyle factors as well that put them at risk for breast cancer, HRT is almost certainly one of the accomplices if not the main perpetrator in the mystery of Marin County.

Mary Lou Williams, M. Ed., is a writer and lecturer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.



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