LEP and osteoarthritis: Leptin serum levels are about five times higher in obese people than in normal individuals, with an average of 40 and 8 ng/ml, respectively.6 Leptin not only controls appetite and body mass, but also takes part in the regulation of endocrine functions, metabolism, reproduction, immunity, cardiovascular pathophysiology, respiratory function, and wound healing, as well as osteoarthritis.7 Leptin acts via its receptors (OBR), which is encoded by the db gene.