Also, FGF23 was positively correlated with D-serine; it is hypothesized that in the chronic renal failure setting, abnormally high expression of FGF23 promotes increased production of D-serine (i.e., the presence of an FGF23/D-serine axis), which overactivates the auditory nerve NMDAR and causes excitatory neurotoxicity, thereby promoting auditory damage. The gene discussed is FGF23; the disease is chronic kidney disease.