Dysregulation of vitamin D metabolism is closely associated with the pathogenesis of various diseases, including vitamin D-dependent rickets type 1A (VDDR-1A), chronic kidney disease-mineral and bone disorder (CKD-MBD), tumor-induced osteomalacia (TIO), granulomatous diseases, and CYP24A1 deficiency-related hypercalcemia. Here, CYP24A1 is linked to hyperinsulinemic hypoglycemia, familial, 4.