SDC4 and breast cancer: Furthermore, we discovered that the pathways involving PTPRM: Ptprm − Ptprm, NRXN: Nrxn1 − Nlgn1, and COLLAGEN: Col1a2 − Sdc4/Cd44 exhibited similar downregulation trends in IC, with signals primarily originating from autocrine and paracrine secretion of BC across all three types of SNHL (Fig. 6).