The Preoperative Paradoxical GH Response to Oral Glucose Load Predicts a Low Risk of Recurrence in Acromegaly

Abstract

Context A paradoxical growth hormone (GH) response to oral glucose load (oral glucose tolerance test [OGTT]) in acromegaly is associated with a milder phenotype. Objective To study whether the GH response to the OGTT predicts the risk of recurrence after initial surgical cure. Methods Retrospective, observational study at 2 tertiary care centers. We investigated 254 patients with acromegaly who were cured by surgery. All patients underwent an OGTT at diagnosis before pituitary surgery. A peak to basal GH ratio ≥120% within 90 minutes was used to distinguish paradoxical (GH-Par) from nonparadoxical responses (GH-NPar) in patients with acromegaly. Cox analysis was used to investigate whether the paradoxical GH response to OGTT was associated with the risk of disease recurrence Results A paradoxical GH response to OGTT occurred in 87 patients (34.3%, termed GH-Par group). Recurrence of acromegaly occurred in 3 patients in the GH-Par group (3.4%) and in 20 patients in the GH-NPar group (12.0%). In the multivariate analysis, the paradoxical GH response to OGTT was significantly associated with a low risk of recurrence (HR 0.18, 95% CI 0.05-0.63; P = .007). Basal GH level at diagnosis was the only other variable associated with the risk of disease recurrence (HR 1.58, 95% CI 1.01-2.47; P = .04). Conclusion Our study demonstrates that a paradoxical GH response to OGTT in the preoperative setting predicts a lower risk of disease recurrence after initial surgical cure. The pattern of GH responsiveness to OGTT is, therefore, useful to predict the long-term outcome of patients with acromegaly.