The largest prospective cohort study of postmenopausal women reported a 34% increase in risk of breast cancer when comparing top to bottom quartiles (> 12 vs. < 7.4 ng/mL) of PRL levels [16]; these findings were similar to results from an earlier study reporting a non-significant increase in risk of 1.34, based on a smaller sample size [17]. Here, PRL is linked to breast carcinoma.