Introduction: Along with the significant increase in the average life expectancy of patients with cystic fibrosis (CF), there are still significant differences in the height, weight, and body mass index (BMI) of patients compared to healthy controls. The association between leptin and fat mass may be an additional factor in weight loss or poor weight gain in CF patients.

Aim: Our objective was to estimate serum leptin concentrations in CF patients aged 10-39 years as well as assess any correlations between leptin and clinical characteristics of CF.

Materials and methods: Leptin serum concentrations after an overnight fast were measured using enzyme-linked immunosorbent assay in 38 CF patients and 16 controls. In all participants' height, weight, BMI, and forced expiratory volume in 1 second (FEV₁) were estimated. Moreover, fasting serum C-reactive protein (CRP) concentrations were also analyzed.

Results: Fasting leptin levels in CF were significantly higher in patients with CF patients (13.9±6.9 vs. 6.5± 2.6 ng/mL, p<0.001) compared to controls. There were no differences in leptin concentration between female and male CF participants (15.7±7.8 vs. 12.2±5.6 ng/mL, p=0.13). Leptin was correlated with age (R=0.64, p<0.001), BMI (R=0.65, p<0.001), FEV₁ (R=-0.49, p<0.01), and CRP (R=-0.73, p<0.001).

Conclusion: Increased serum leptin level was associated positively with age and nutritional status, as well as negatively with FEV₁ and CRP in patients with CF. The results of our study suggest that reduced pulmonary function in CF may be related with elevated level of leptin, while weight loss may be associated with decreased level of leptin.