GH replacement treatment improves most of these abnormalities (10–14); however, due to the high cost of GH therapy (14, 15) and to the concerns of potential long-term risks, particularly the development of diabetes mellitus or malignancies, it is crucial to establish a correct diagnosis in order to offer GH replacement to truly GH-deficient adults (1, 12, 14). This evidence concerns the gene GH1 and diabetes mellitus.