Leptin, Leptin Receptor Concentrations and Free Leptin Index (FLI) in Polish Healthy Children and Adolescents.

Background: Leptin physiology in children is crucial for diagnosing and managing pediatric endocrine and metabolic disorders. The aim of this study was to assess the values of leptin, leptin receptor (sOB-R), and free leptin index (FLI) depending on age and sex in healthy Polish children and adolescents.

Materials and methods: A total of 236 children and adolescents aged 1-18 years were recruited. Leptin and leptin receptor concentrations were determined by immunoenzymatic methods. FLI values were calculated as leptin divided by sOB-R concentrations. In 114 children between the ages of 5 and 10 years, a measurement of fat mass was assessed by dual-energy X-ray absorptiometry.

Results: The studied groups of girls and boys were of similar age and did not differ in terms of weight, height, body mass index (BMI), BMI Z-score values, or leptin receptor concentrations. Leptin concentrations and FLI were higher by about 50% (p=0.006; p=0.051, respectively) in girls than boys. Positive correlations were found between leptin and age, BMI, and BMI Z-score values (r=0.562, r=0.563, p=0.397; p<0.001, respectively), and even stronger between FLI and age, BMI, and BMI Z-score values (r=0.670, r=0.632, p=0.409; p<0.001, respectively).

Conclusions: The results concerning leptin and leptin receptor concentrations and FLI values in healthy individuals may be useful in clinical practice in early identification of children and adolescents with an unfavorable adipokine profile resulting in a predisposition to the development of obesity and obesity-related complications. These markers may also be helpful in monitoring therapy effectiveness in patients with obesity, diabetes, and metabolic syndrome.