Animals with Klotho deficiency show signs of FGF-23 deficiency with high serum phosphate and calcitriol concentration.99 Transgenic mice that overexpress Klotho live longer than control mice;100 this has also been seen in people confirming Klotho as an antiaging factor.86,101 Mice with the negative mutated Klotho gene show hyperphosphatemia, increased serum calcitriol concentrations, development of extraskeletal calcification, rapid aging, and early death.100–102 Klotho may also have phosphate regulatory effects independent of FGF-23.103. Here, FGF23 is linked to hyperinsulinemic hypoglycemia, familial, 4.