SHBG and breast cancer: Thus, a decrease in the level of SHBG in the organism (determined by SHBG-lowering genetic determinants) leads to an increase in the concentration of bioavailable (“free”) testosterone and estrogens and, accordingly, causes an increase in their pro-oncogenic phenotypic effects and a decrease in the independent anti-oncogenic effects of SHBG, which ultimately has a risky value for BC development.