We have shown that eight out of nine studied polymorphisms affecting the concentration of SHBG in the organism according to GWAS data (rs17496332 PRMT6, rs780093 GCKR, rs10454142 PPP1R21, rs3779195 BAIAP2L1, rs440837 ZBTB10, rs7910927 JMJD1C, rs4149056 SLCO1B1, and rs8023580 NR2F2 [23]) interact between by themselves and determine the predisposition to BC. The gene discussed is PPP1R21; the disease is breast cancer.