Other genes such as MC4R, leptin and leptin receptor, Ghrelin (GHRL), peroxisome proliferator-activated receptor gamma (PPARG), oxytocin receptor (OXTR), prohormone convertase-1 and proopiomelanocortin have been implicated in human obesity and will be discussed elsewhere in this journal issue. The gene discussed is PCSK1; the disease is obesity due to melanocortin 4 receptor deficiency.