Leptin, Soluble Leptin Receptors, Free Leptin Index, and Their Relationship with Insulin Resistance and BMI: High Normal BMI is the Threshold for Serum Leptin Increase in Humans - Owecki, M.; Nikisch, E.; Miczke, A.; Pupek-Musialik, D.; Sowiński, J. (Hormone and Metabolic Research, 2010)