GIPR and obesity due to melanocortin 4 receptor deficiency: Genome-wide association studies (GWAS) have revealed that common variants in the GIPR are associated with obesity (Vogel et al., 2009; Speliotes et al., 2010) and impaired glucose- and bone mineral homeostasis (Sauber et al., 2010; Saxena et al., 2010; Torekov et al., 2014).