To achieve this, we modelled physiologically relevant levels of oestradiol: 1) very low levels seen in aromatase inhibitor use in postmenopausal women; 2) low levels that we would expect in perimenopausal women; and 3) higher levels that we would find in premenopausal women in mice in the absence of tumour cells or before tumour cell dissemination into the circulation ± Zol. The gene discussed is CYP19A1; the disease is neoplasm.