Of the nine studied loci, eight polymorphisms of SHBG-related genes were part of the BC-risk interlocus models, such as rs780093 GCKR, rs17496332 PRMT6, rs3779195 BAIAP2L1, rs10454142 PPP1R21, rs7910927 JMJD1C, rs4149056 SLCO1B1, rs440837 ZBTB10, and rs8023580 NR2F2 (Table 2). The gene discussed is PPP1R21; the disease is breast cancer.