TCF7L2 and type 2 diabetes mellitus: Genome-wide association studies (GWASs) have identified over 400 loci influencing T2D risk, many of which regulate insulin secretion (Glucokinase [GCK], Transcription Factor 7-Like 2 [TCF7L2]) or insulin sensitivity (Peroxisome Proliferator-Activated Receptor Gamma [PPARG], Insulin Receptor Substrate 1 [IRS1]) [17,18,19,20].