PCSK1 and obesity due to melanocortin 4 receptor deficiency: The elevated risk of obesity has been linked to individual single nucleotide polymorphisms (SNPs) in human genes encoding proteins such as adipocyte-, C1q-, and collagen domain-containing (ADIPOQ) fat mass- and obesity-associated gene (FTO), leptin (LEP), leptin receptor (LEPR), insulin-induced gene two (INSIG2), melanocortin four receptor (MC4R), proprotein convertase subtilisin/kexin type one (PCSK1), and peroxisome proliferator-activated receptor gamma (PPARG) [18,19].