A pooled analysis of three large prospective cohort studies reported a small increased risk for breast cancer in women with high normal or above normal levels of prolactin (>17.6 ng/mL) compared to women with below normal levels (≤9.8 ng/mL) (RR = 1.3, CI = 1.1–1.6, p-trend = 0.002) (Tworoger et al., 2007). The gene discussed is PRL; the disease is breast carcinoma.