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Perspect Biol Med. 1989 Autumn;33(1):86-106.

The risks of oral contraceptives and estrogen replacement therapy.

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Nephrology Program, University of Chicago, Pritzker School of Medicine, Illinois 60637.



The benefits and risks of both oral contraceptives and estrogen replacement therapy (ERT) are evaluated by summarizing briefly the results of the most evidential studies on breast, ovarian, endometrial, and hepatobiliary cancer, heart attack, stroke and venous thromboembolism. The methods used to estimate risk ratios, prospective random-allocation, double-blind trials, and retrospective case- controlled studies, are explained briefly. The ERT used today resemble sequential oral contraceptives, except that only 10-20 mcg ethinyl estradiol is taken for 25 days, and progestins are used on the last 10 days. Breast cancer risk is not different in pill users from nonusers, based on the U.K. General PRactitioner, Oxford Family Planning, Harvard nurses or U.S. SEER National Cancer Institute studies. Studies on ERT and breast cancer are mixed, but only injected estrogens raised the risks. Ovarian cancer is prevented by pill use in proportion to length of use. No studies were reported for ERT. The risk of hepatic cancer is 3.8 to 7.8 higher in pill users, but the number of cases is so rare that this should not affect prescriptions. Neither pill nor ERT raise the risk of myocardial infarction, and after premature surgical menopause, ERT lowers the risk. Based on studies done in the 1970s, oral contraceptives raise the risk of thrombotic stroke while women are taking them, from 10-13/100,000 to 41/100,000. ERT has no clear association with stroke. Similarly, orals increase the risk of venous thromboembolism, 8-fold in the Oxford Family Planning study published in 1986, although the absolute numbers are very small. ERT had no effects no risk of thromboembolism according to the lipid Research, Framingham and Nachtigall studies.

[Indexed for MEDLINE]

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