The strong association between PCSK1 and obesity is due to its function; mutation in this gene leads to the misprocessing of melanocortin peptides, which alters the role of hormones and neuropeptides important for thermogenesis and feeding and involved in glucose homeostasis, fat oxidation, and energy expenditure [5,6,7,37]. This evidence concerns the gene PCSK1 and obesity due to melanocortin 4 receptor deficiency.