Only, the IGF-1 upper limit of normal range, and the random IGF-1 and GH value showed the best accuracy distinguishing between acromegaly and NFPAs (AUC = 1.00, 100% sensitivity and specificity, AUC = 0.98, 92% sensitivity and 96% specificity, and AUC = 0.97, 92% sensitivity and 89% specificity, respectively; for all p < 0.001). This evidence concerns the gene GH1 and acromegaly.