Objective: We investigated whether or not serum levels of the soluble leptin receptor (sOB-R) and leptin are related to anthropometric and metabolic changes during pubertal development of children and adolescents with type 1 diabetes mellitus. Design and methods: Blood levels of sOB-R, leptin and HbA1C, as well as body-mass index (BMI), diabetes duration and daily insulin doses, were determined in 212 (97 girls; 115 boys) children with type 1 diabetes mellitus and compared with the sOB-R serum levels in 526 healthy children and adolescents. Results: OB-R serum levels and parallel values of the molar ratio between sOB-R and leptin were significantly higher in children with diabetes than in normal children (P , 0.05) in almost all investigated Tanner stages. Furthermore, in the entire group of patients, we demonstrated statistically significant correlations (P , 0.02) between sOB-R and the duration of diabetes (r ¼ 0.30), HbA1c levels (r ¼ 0.32) and the insulin dose (r ¼ 0.18). Multiple-regression analysis revealed that HbA1c (12.4%), height (7.9%) and duration of diabetes (8.7%) contributed to 29% variance of sOB-R in diabetic children. Conclusions: Our data suggest that poor glycemic control in diabetes may lead to increased serum levels of sOB-R. This regulation of sOB-R appears to be independent of leptin, but may have an impact on leptin action. The consequently developing molar excess of sOB-R related to leptin could reduce leptin sensitivity and may, therefore, influence leptin-related anthropometric and metabolic abnormalities.European Journal of Endocrinology 151 475-481