LEP and obesity due to melanocortin 4 receptor deficiency: Pre-pubertal children with obesity and with low z-scores of circulating leptin levels show significantly higher liver enzyme levels of AST (17.3 ± 6.8 vs. 14.7 ± 5.5 U/l, p<0.05) and ALT (18.4 ± 9.1 vs. 14.2 ± 8.1 U/l, p<0.05), higher fasting insulin (16.8 ± 13.4 vs. 13.9 ± 10.0 mU/l, p<0.05) and c-peptide levels (2.0 ± 1.1 vs. 1.6 ± 0.7 μg/l, p<0.05), higher triglyceride (114.9 ± 76.7 vs. 98.8 ± 58.3, p<0.05), higher total cholesterol and lower HDL cholesterol levels (44.7 ± 8.0 vs. 48.8 ± 9.4 mg/dl, p<0.05) compared to children with normal z-scores for circulating leptin levels (Table 2).