The cutoff value of 3 μg/L has also been recommended to discriminate between normal response and severe AGHD in the GST13–16,26, but a lower threshold of 1 μg/L was recently proposed for overweight/obese subjects, as obesity blunts GH response to glucagon stimulation28,36. This evidence concerns the gene GCG and obesity due to melanocortin 4 receptor deficiency.