Pubertal stage significantly and independently impacts C-peptide levels at type 1 diabetes diagnosis along with body mass index and age

Assessment of beta-cell function in type 1 diabetes (T1D) has important implications in both clinical and research settings. Studies demonstrating the extent to which puberty influences C-peptide levels are scarce. The aim of this study was to evaluate the influence of pubertal stage, along with age and body mass index (BMI), on multiple C-peptide measures at T1D diagnosis. This study included 275 consecutive children aged between 1 and 18 years with newly diagnosed T1D. Fasting, prandial, and area under the curve (AUC) C-peptide, estimated using fasting and prandial C-peptide levels, were analyzed. Generalized linear regression models were utilized. Median age at diagnosis was 7.9 (1.1-17.3) years, and mean BMI standard deviation score (SDS) was - 0.4 +/- 1.4. Of the patients, 66% were prepubertal. Median fasting and prandial C-peptide levels at diagnosis were 0.26 (0.05-1.8) ng/mL and 0.43 (0.05-3) ng/mL, respectively. Fasting C-peptide was almost perfectly correlated with prandial C-peptide (r(s) = 0.80, P < 0.001). Fasting, prandial, and AUC C-peptide were positively related with BMI SDS, age, and pubertal stage at diagnosis (P < 0.001 for all). All the associations persisted when the variables were included as independent variables in regression models. Conclusions: Pubertal stage significantly and independently impacts C-peptide levels at T1D diagnosis along with body mass index and age. The adjustments demonstrating the extent to which puberty influences C-peptide levels in new-onset T1D are presented. Our observations underline the existence of distinct endotypes of T1D characterized by differing immunopathological courses.