Current use of metformin in addition to insulin in pediatric patients with type 1 diabetes mellitus: an analysis based on a large diabetes registry in Germany and Austria

Background With increasing obesity in childhood and adolescence, weight gain, and insulin resistance become also more frequent in patients with type 1 diabetes mellitus (T1DM). Especially during puberty, insulin therapy often has to be intensified and higher insulin doses are necessary. Some studies point to a beneficial effect of metformin in addition to insulin in these patients. In order to describe current practice and possible benefits, we compared pediatric T1DM patients with insulin plus metformin (n = 525) to patients with insulin therapy only (n = 57 487) in a prospective multicenter analysis. Methods Auxological and treatment data from 58 012 patients aged <21 yr with T1DM in the German/Austrian Diabetes Patienten Verlaufsdokumentation (DPV) registry were analyzed by multivariable mixed regression modeling. Results Patients with additional metformin were older [median (interquartile range)]: [16.1 (14.1–17.6) vs. 15.2 (11.5–17.5) yr] with female preponderance (61.0 vs. 47.2%, p < 0.01). They had higher body mass index-standard deviation score (BMI-SDS) [+2.03 (+1.29 to +2.56) vs. +0.51 (−0.12 to +1.15); p < 0.01] and glycated hemoglobin (HbA1c) (9.0 vs. 8.6%, p < 0.01). Hypertension (43.7 vs. 24.8%) and dyslipidemia (58.4 vs. 40.6%) were significantly more prevalent. Adjusted insulin dose was significantly higher (0.98 vs. 0.93 IU/kg bodyweight). In a subgroup of 285 patients followed-up longitudinally (average treatment period 1.42 yr), addition of metformin resulted in a slight reduction of BMI-SDS [−0.01 (−2.01 to +1.40)], but did not improve HbA1c or insulin requirement. Conclusion Additional metformin therapy in T1DM is primarily used in obese females. Additional therapy with metformin was associated with minor benefits.