In another case control study, Tikk et al. analysed the association of PRL prediagnostic circulatory levels with the risk of breast cancer through menopause status, HRT therapy with the use of a blood donation system and the hormone receptor status of the breast tumours in 2250 breast cancer cases, the study found that the risk of breast cancer among postmenopausal women was higher because of prolactin overexpression. Here, PRL is linked to breast cancer.