There are several studies in the periodontal literature examining GCF and salivary levels of growth factors for periodontal disease diagnosis including of epidermal growth factor (EGF),[76] transforming growth factor-α (TGF-α) and TGF-β,[74] platelet-derived growth factor (PDGF),[77] and vascular-endothelial growth factor (VEGF) [78]. The gene discussed is EGF; the disease is periodontal disorder.