Cytochrome P450c17 alpha gene (CYP17) polymorphism predicts use of hormonereplacement therapy

We investigated whether a polymorphism in the cytochrome P450c17 alpha gene (CYP17), which is associated with higher endogenous hormone levels, Influe nces the use of hormone replacement therapy (HRT). The study included 749 p ostmenopausal women ages 44-75 years at baseline randomly selected from a l arger multiethnic cohort. African-American, Japanese, Latina, and white wom en were included in the study. Women who carry the CYP17 A2/A2 genotype wer e about half as likely as women with the A1/A1 genotype to be current HRT u sers (odds ratio = 0.52; 95% confidence interval, 0.31-0.86). This associat ion was present in all four racial/ethnic groups and for women above and be low the median weight of 150 pounds. These findings suggest that the actual risk of breast cancer associated with HRT use may be higher than previousl y reported.