GHRP-2 Test Shows Promise as Safer Alternative for Adrenal Axis Assessment

The hypothalamic-pituitary-adrenal (HPA) axis is vital for regulating stress response and metabolism, and its proper function is crucial for overall health. Assessing its function, particularly pituitary-adrenal responsiveness, is essential for diagnosing conditions like adrenal insufficiency. The Insulin Tolerance Test (ITT) is currently considered the gold standard for this assessment but carries significant risks due to induced hypoglycemia. This pilot study directly compared the efficacy and safety of the Growth Hormone-Releasing Peptide-2 (GHRP-2) test against the ITT for evaluating pituitary-adrenal axis function.

Both the ITT and GHRP-2 tests significantly stimulated cortisol and ACTH secretion, demonstrating their effectiveness in activating the HPA axis. The GHRP-2 test induced a peak cortisol response of 450 ± 50 nmol/L, which was comparable to the ITT's peak of 480 ± 60 nmol/L (p=0.32), indicating similar stimulatory capacity. ACTH levels also showed a strong correlation between the two tests, with a peak ACTH increase of 2.8-fold for GHRP-2 compared to 3.1-fold for ITT (p=0.18). > Importantly, the GHRP-2 test was associated with significantly fewer adverse events, with only 10% of participants experiencing mild dizziness, compared to 60% experiencing symptomatic hypoglycemia during the ITT (p<0.001). The correlation coefficient between the peak cortisol responses of the two tests was r=0.85 (p<0.001), indicating strong agreement in their diagnostic potential.