TCF7L2 and metabolic syndrome: TCF7L2 has been widely studied for its association with metabolic-related diseases, such as type 2 diabetes mellitus (Mayans et al., 2007; Villareal et al., 2010; Shokouhi et al., 2014; Zhu et al., 2017; Zhou et al., 2019), obesity (Al-Daghri et al., 2014), metabolic syndrome (DeMenna et al., 2014), and cancers (Folsom et al., 2008; Chen et al., 2013) in various populations.