The increase in insulin requirement at the onset of adolescence is compensated by an increase of insulin secretion. This metabolic pattern persists during adolescence but is no longer present in adults. It is supposed to depend on a decrease of insulin sensitivity of uncertain origin. We compared the metabolic pattern of late adolescent girls (13-16 year old) with young women (21-30 year old) with similar body mass indexes, testing subjects with iv glucose tolerance test (IVGTT) (glucose 0.33 g/kg) and arginine test (ATT) (arginine 30 g in 30 min). In late adolescent vs adult women we observed: i) IVTT: similar k of glucose tolerance and higher insulin and C-peptide responses; ii) ATT: unmodified plasma glucose, insulin and glucagon values, higher GH plasma levels; iii) in adolescent girls GH and CPR incremental areas significantly correlated (r = 0.755, p less than 0.05). These data show that: i) the adolescent pattern of glucose metabolism persists after completion of sexual development and, ii) there is a positive correlation between GH response to arginine and beta-cell response to glucose. So GH should play a role in the impairment of glucose metabolism during adolescence.