In this regard, studies in mice showed that FGF23 reduced the expression of cyp27b1 and stimulated the expression of cyp24a1, in a finely balanced homeostatic mechanism Thus, it is conceivable that the high levels of FGF23 may contribute to the impaired conversion of serum 25(OH)D in 1,25(OH)D in patients with hypoparathyroidism [14, 88]. This evidence concerns the gene FGF23 and hypoparathyroidism.