CYP2D6 and obesity due to melanocortin 4 receptor deficiency: BMI in our studied population showed a direct relationship with the transcriptional changes (downregulated) observed on selected genes (APC, ARNT, CYP2D6, LEPR, LRP12, and MYC) (Fig. 5), all of which are closely linked to the development of cancer or obesity (Ghosh et al., 2015).