One AIP mutation carrier in our kindred, the proband's male cousin (III.b), who has no symptoms of acromegaly and has normal MRI, was found with slightly increased IGF-1 (1.03 × ULN), but his GH nadir on OGTT was 0.28 μg/L, and a repeated IGF-1 later was normal. The gene discussed is GH1; the disease is acromegaly.