Because pharmacologic administration of recombinant FGF21 elicits multiple metabolic benefits in animal models, including decreased body weight, improved insulin and leptin sensitivity, and decreased hepatic steatosis, as reviewed by [9,10,11,138], several pharmaceutical companies have now developed FGF21 analogues for clinical use in metabolic disease [11,139,140,141]. The gene discussed is LEP; the disease is fatty liver disease.