Breast cancer risk and history of selected medical conditions linked with female hormones.

The relation between history of several medical conditions and procedures and risk of breast cancer was evaluated in data from a hospital-based case-control study of 2663 cases of breast cancer and 2344 controls with acute conditions unrelated to any of the established or potential risk factors for breast cancer. Whereas previous diagnosis of diabetes mellitus, thyroid disease, hypertension at any age, hyperlipidaemia, cholelithiasis, pelvic inflammatory disease and physician-diagnosed subfertility were unrelated to cancer risk, history of severe obesity in postmenopausal women (odds ratio [OR] 1.4), benign breast disease (OR 1.8) and history of breast biopsies (OR 2.4) were associated with significant risk elevation. Conversely, lifelong history of menstrual irregularities (OR 0.6) seemed to confer some protection against onset of breast cancer. This study supports the hypothesis that, unlike endometrial cancer, breast cancer risk is not enhanced by medical conditions known or suspected to be linked with female hormones, with the exception of benign breast disease and severe overweight in postmenopausal women.