MC4R and obesity due to melanocortin 4 receptor deficiency: Among the six leptin-associated loci, three genes (MC4R, BDNF, and PCSK1) are known to be involved in the hypothalamic leptin–melanocortin pathway [9, 17, 30], thus it is not surprising that those three loci are found to be associated with obesity-related traits and leptin levels in our pediatric setting.