To determine whether the addition of the thiazoladinedione, pioglitazone, to standard therapy improves metabolic control in adolescents with type 1 diabetes (T1D) and clinical evidence of insulin resistance.

Randomized, placebo-controlled 6-month 2-site trial of pioglitazone therapy in 35 adolescents with T1D, high insulin requirements (>0.9 U/kg/d), and suboptimal metabolic control (A1c 7.5%-11%), with the primary outcome of change in A1c. Secondary outcomes include change in insulin dose, body mass index (BMI), lipids, and waist and hip circumference.

Metabolic control (A1c) was improved at 6 months in all subjects (P = .02). There was no significant difference between the pioglitazone and placebo treatment groups at 6 months in either change in A1c (−0.4% ± 0.9% and −0.5% ± 1.2%, respectively) or insulin dose. BMI SDS increased by 0.3 ± 0.3 (kg/m²) in the pioglitazone group and remained unchanged in the placebo group (P = .01). There was no significant difference in change in any lipid parameters between the pioglitazone and placebo groups at 6 months.

Adjunctive pioglitazone therapy was not effective in improving glycemic control in adolescents with T1D. Pioglitazone was associated with increased BMI.