BACKGROUND The weak androgen oxandrolone (Ox) may increase height but may also affect glucose metabolism in girls with Turner syndrome (TS). METHODS In a randomized, placebo-controlled, double-blind study, we assessed the effect of Ox at a dosage of either 0.06 or 0.03 mg/kg/day on glucose metabolism in 133 growth hormone (GH)-treated girls with TS. Patients were treated with GH (1.33 mg/m(2)/day) from baseline, combined with placebo (Pl) or Ox from the age of 8, and estrogens from the age of 12. Oral glucose tolerance tests (OGTT) were performed, and HbA1c levels were measured before, during, and after discontinuing Ox/Pl therapy. RESULTS Insulin sensitivity, assessed by the whole-body insulin sensitivity index (WBISI) decreased during GH+Ox/Pl (p = 0.003) without significant differences between the dosage groups. Values returned to pre-treatment levels after discontinuing GH+Ox/Pl. On GH+Ox, fasting glucose was less frequently impaired (Ox 0.03, p = 0.001; Ox 0.06, p = 0.02) and HbA1c levels decreased more (p = 0.03 and p = 0.001, respectively) than on GH+Pl. CONCLUSIONS We conclude that in GH-treated girls with TS, Ox at a dosage of 0.03 or 0.06 mg/kg/day does not significantly affect insulin sensitivity. Insulin sensitivity decreases during GH therapy, to return to a pre-treatment level after discontinuing therapy.