ObjectiveThe beneficial effects of metformin in peripubertal adolescents and rosiglitazone in overweight type1 diabetic subjects, though modest have been demonstrated. This study was designed to analyze the effect of pioglitazone as an adjunctive therapy in post-pubertal lean T1DM. Patients and methodsSixty type1 diabetic subjects with duration of illness of a year or more with body mass index between 18 and 24.9kg/m2 were randomly assigned to receive either 30mg pioglitazone or placebo once daily for 6 months. The study was double-blinded placebo controlled with 30 subjects in each group, matched for age, sex, anthropometric and metabolic parameters. At the end of the study period, plasma glucose levels, HbA1c, lipids and insulin requirement were compared between the two groups. ResultsA significant improvement in post-prandial plasma glucose (PPPG) levels (9.1±1.7 and 8.4±1.3mmol/L, p=0.002) and HbA1c (7.08±0.48 and 6.86±0.45%, p=0.001) were observed in the pioglitazone treated group, but not in the placebo treated group (8.3±1.8 and 7.8±1.8mmol/L, p=0.06 and HbA1c 7.3±0.37 and 7.24±0.33%, p=0.74, respectively). However, the mean decrease in PPPG and HbA1c levels between groups corrected for baseline values at the end of study was significant only for the later (HbA1c −0.22±0.29 and −0.06±0.49, p=0.03), while for the former, it got attenuated (PPPG −0.69±1.1 and −0.48±1.36, p=0.68). There was no alteration in body weight, body mass index, insulin requirement, blood pressure and lipid profile in both the groups at the end of the study. ConclusionPioglitazone is modestly effective adjunct to insulin therapy in lean type1 diabetic subjects. It improves post-prandial glucose levels and HbA1c without alterations in body weight and insulin requirement.