In addition, loss-of-function mutations of the Cell Division Cycle 73 (CDC73) or of the Calcium-Sensing receptor (CaSR) genes and, very recently, gain-of-function mutations of the Glial Cells Missing Homolog 2 (GCM2) gene, have also been detected in a few FIHP kindreds [10]. This evidence concerns the gene CDC73 and familial isolated hyperparathyroidism.