As opposed to the outcomes of cross-sectional studies, a case-control study performed by Martínez et al. [42] reported that the serum levels of Nrg4 were elevated in participants with obesity and insulin resistance, and it was positively associated with insulin resistance and high-sensitive C-reactive protein (hs-CRP), but not with the markers of liver injury. This evidence concerns the gene NRG4 and obesity due to melanocortin 4 receptor deficiency.