Dusso et al. and Cozzolino et al. reported that parathyroid hyperplasia was exacerbated by hyperphosphatemia due to increased expression of transforming growth factor-alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) in the PTGs using the 5/6 nephrectomized rats [46, 47]. The gene discussed is EGFR; the disease is hyperphosphatemia.