Examples are vitamin D-resistant disorders (e.g., vitamin D-resistant rickets; genetic abnormalities of CYP enzymes), hypoparathyroidism, genetic and acquired hypophosphataemic osteomalacia, renal osteodystrophy, migraine, psoriasis, malabsorption, obesity, osteomalacia secondary to hepatic impairment, etc. The gene discussed is PPIG; the disease is obesity due to melanocortin 4 receptor deficiency.