In a subsequent study, 206 women with BRCA1 or−2 mutations had serum OPG levels measured, were divided into low OPG (mean 62.9 pg/ml; range 4.2–94.5 pg/ml) or high OPG (mean 168.1 pg/ml; range 95.5–547.7 pg/ml) groups, and were followed for the development of breast cancer. The gene discussed is BRCA1; the disease is breast cancer.