However, other factors are also associated with SHPT, including Klotho deficiency, a decrease of fibroblast growth factor (FGF) receptor 1 expression [23] and a decrease in serum 1,25-dihydroxyvitamin D associated with excessive FGF-23 bone synthesis [24]. This evidence concerns the gene FGF23 and hyperinsulinemic hypoglycemia, familial, 4.