The objective was to determine the effect of metformin on the concentrations of resistin and other markers of insulin resistance or inflammation (C-reactive protein, cytokines, body weight, HbA1c, among others) in minors with glucose intolerance. Patients aged 4 to 17 years with glucose intolerance were studied. They were randomized to receive 850 mg of either metformin or placebo twice daily for 12 weeks, during which all followed an iso-caloric diet and an exercise program. High sensitivity C-reactive protein, TNF-alpha, IL-6, IL1-beta, resistin, leptin, adiponectin, glucose, insulin, HbA1c, lipid profile and transaminases were measured at the beginning and at the end of the period. Fifty-two patients were included, 11.9±2.6 years old; 28 (12 males/16 females) received metformin and 24 placebo (11 males/13 females). Baseline characteristics were similar between groups (except for body mass index, which in the metformin group was slightly higher). Percentage weight loss was greater in the metformin group (-5.86% vs 2.75%, P