While no undesirable actions of leptin have yet been reported in decade- long replacement therapy in patients with mutation of the leptin gene [52], and Metreleptin is now approved by the U.S. Food and Drug Administration (FDA) for the treatment of severe metabolic abnormalities associated with lipodystrophy [53], its efficacy (and safety) in other metabolic disorders will still need to be studied. This evidence concerns the gene LEP and metabolic disease.