However, the NHS study evaluated prolactin levels among premenopausal and postmenopausal women and found no difference in risk of breast cancer by menopausal status: premenopausal (RR 1.3, 95% CI 0.9–1.9) vs. postmenopausal (RR 1.3, 95% CI 1.0–1.8) women [16,29]. This evidence concerns the gene PRL and breast cancer.