Do patients with an elevated IGF-1 level and features of acromegaly need to have confirmatory growth hormone suppression testing with OGTT?

OGTT is not always needed. In the presence of clinical features of acromegaly, a frankly elevated IGF-1, and a pituitary adenoma visible by MRI glucose suppression test is not necessary.

I typically initiate the screening for acromegaly by checking the IGF-1 level in patients with dx pituitary adenoma or clinical suspicious of acromegaly. In addition, I include baseline GH level assessment as part of the initial evaluation. In cases where serum IGF-1 levels are mildly elevated or equivocal, patient does not have the typical features of acromegaly, I proceed to confirm the diagnosis by examining the lack of GH suppression with hyperglycemia. Thus, in most cases, obtaining OGTT is not necessary.