FGF23 and X-linked hypophosphatemia: Genetic testing, such as the Renasight panel screening 397 genes including PHEX, FGF23, and CYP27B1, rules out hereditary mimics like X-linked hypophosphatemia (XLH) or vitamin D-dependent rickets, with negative results supporting acquired etiologies like TIO; whole-exome sequencing further excludes rare variants [16].