FGF23 and hyperparathyroidism: These modifications are associated with a progressive reduction in the expression of receptors for calcium (CaSR), calcitriol (VDR), and FGF-23 (FGFR1-Klotho), leading to a reduced sensitivity in the parathyroid cells to the inhibitory effect of calcium, calcitriol, and FGF-23 and a worsening of hyperparathyroidism [17,18].