Porkajac and colleagues studied GH and IGF-1 assay performance close to cut-off values for active acromegaly and submitted serum samples known to give borderline results to 23 centers for IGF-1 assessment and reported more than a 2-fold variation in IGF-1 cut-off for the ULN range measured in different laboratories and the diagnosis of acromegaly was inaccurately excluded in 30% of samples assayed for IGF-1 [17]. The gene discussed is GH1; the disease is acromegaly.