I never thought I'd write the following sentence, but the evidence has become pretty overwhelming: Unless a woman has a history of breast cancer or has some other condition aggravated by estrogen, the benefits of postmenopausal hormone replacement therapy (HRT) far outweigh the risks.
For the past 15 years, I've been very skeptical about the safety of estrogen in both HRT (estrogen plus the hormone progestin), which women use to ease the passage into menopause, and in birth control pills (see Pilling Time). Many studies have shown that HRT increases the risk of breast cancer in postmenopausal women; others have shown no association. On balance, I felt that estrogen was a bad idea.
However, studies have also shown that estrogen helps prevent heart disease, osteoporosis (postmenopausal bone-thinning), and colon cancer, and can even reduce the risk of Alzheimer's. Women faced a stark decision: What are you more afraid of? Breast cancer? Heart disease? Osteoporosis? But the terms of the debate have changed -- and as a result, I've changed my tune.
It's been a long road for yours truly. For years, I've been astonished at the number of scientists who gamely argued that HRT poses no breast cancer risk. That seemed ridiculous. For decades, estrogen has been widely recognized as a stimulator of breast tumors in both animals and humans. It stood to reason that as growing numbers of women took estrogen, over time, we would see a steady increase in breast cancer -- and we have, at a rate of about 1 percent per year. Contrary to what some experts have claimed, the increase cannot be fully explained by earlier detection (i.e., mammography).
In addition, it has become increasingly clear that compounds which mimic estrogen -- chemicals unrelated to the hormone but that bind to cellular estrogen receptors -- have been disrupting mammalian wildlife reproduction and, quite possibly, contributing to the higher incidence of human breast cancer. (See "Breast Cancer Cover-Up," May/June 1994.)