LEP and chronic obstructive pulmonary disease: The studies included here approach the association of leptin levels with BMD in several pathologies: chronic obstructive pulmonary disease [36,40], chronic liver disease [24,37], chronic renal disease [37], type 2 diabetes mellitus [45], inflammatory bowel disease (IBD) [38], idiopathic scoliosis [33,46], Duchenne muscular dystrophy [34], and hypoleptinemia [39].