HyperfunctionSerum IGF-1Normal levels: acromegaly / gigantism is excludedElevated levels (for sex and age): OGTT (75 g) should be performed for GH. If there is lack of GH suppression to <1 ng / ml or <0.4 ng / ml with ultrasensitive assays, the diagnosis is confirmedHypofunctionAdultsSerum IGF-1: In patients with more than 3 pituitary hormonal deficiencies, a low IGF-1 is diagnostic of DGHA. If there are <3 hormonal deficiencies and low IGF-1 levels, a stimulus test should be performed (≥ 2 abnormal tests confirm the diagnosis). This evidence concerns the gene GH1 and acromegaly.