Objective: The role of exercise testing in the assessment of GH deficiency (GHD) in adult patients is currently unclear. This study aimed at evaluating the diagnostic value of exercise-induced GH levels in the detection of severe GHD in adult patients.
Methods: Fourteen patients confirmed to have severe GHD according to current guidelines and 20 healthy control individuals (CI) exercised for 120 min at 50-60% of their individual VO2(max). GH was measured before and every 30 min throughout exercise. The diagnostic value of predicting GHD was assessed by performing receiver operating characteristics (ROC) analysis for each time point of GH assessment. To optimise comparability within the study population a sub-analysis with ten individuals specifically matched for gender, age, body mass index and waist was performed.
Results: Exercise-induced GH secretion was significantly lower in patients with GHD than in CI (P<0.001). Area under the ROC curve (AUC(ROC)) was 0.954±0.033, 0.993±0.009, 0.989±0.012 and 0.992±0.009 for the overall population and 0.870±0.086, 0.980±0.024, 0.970±0.034 and 0.978±0.027 for the matched individuals at 30, 60, 90 and 120 min of exercise respectively. At 60 min of exercise a cut off GH value of 2.4 ng/ml translates into a sensitivity of 100% and a specificity of 95 and 90% in the diagnosis of GHD for the overall population and matched individuals respectively.
Conclusion: GH assessment during a standardised aerobic exercise of moderate intensity is a reliable test with high diagnostic accuracy in predicting severe GHD in adult individuals. Based on the current findings exercise duration of 60 min appears to be sufficient for diagnostic purposes.