IGF1 and acromegaly: Obviously, the concentrations in these individuals do not deviate much from the ULN, but IGF-1 is also not very elevated in patients with acromegaly and nadir GH between 0.4 and 1 μg/L [up to 2/3 have IGF-1 ≤ 2 x ULN (2,10,11)], and the intensity of IGF-1 elevation is therefore little useful for this distinction.