Thus, the high prevalence of comorbidities associated with acromegaly in the general adult population, the fact that even individuals without disease can have slightly elevated IGF-1 and nadir GH > 0.4 μg/L in the OGTT and the rarity of acromegaly may explain why even the combination of findings (suspicious clinical scenario (1-5), elevated IGF-1, nadir GH > 0.4 μg/L) can have a low positive predictive value. This evidence concerns the gene GH1 and acromegaly.