Assessment of anterior pituitary reserve capacity based on growth hormone response to growth hormone-releasing peptide-2 test in the elderly

Objective: The growth hormone (GH)-releasing peptide-2 (GHRP-2) test is relatively safe among endocrine stimulation tests for the elderly. We investigated whether anterior pituitary function in elderly patients could be assessed on the basis of GH response to the GHRP-2 test.

Design: Sixty-five elderly patients aged 65 years and older with non-functioning pituitary neuroendocrine tumor (PitNET) who underwent pituitary surgery and preoperative endocrine stimulation tests were classified into the "GH normal group" and "GH deficiency group" based on GH response to the GHRP-2 test. The baseline characteristics and anterior pituitary function were compared between the groups.

Results: Thirty-two patients were assigned to the GH normal group and 33 to the GH deficiency group. The cortisol and adrenocorticotropic hormone (ACTH) results in the corticotropin-releasing hormone test were significantly higher in the GH normal group than in the GH deficiency group (p < 0.001). The relationship between the cortisol and ACTH results and the GH response revealed significant correlations (p < 0.001). In addition, receiver operating characteristic curve analysis identified that the optimal cut-off point for a peak GH level in the correlation between adrenocortical function and GH response to the GHRP-2 test was 8.08 ng/mL (specificity 0.868, sensitivity 0.852).

Conclusion: The present study indicated that adrenocortical function was significantly correlated with GH response to the GHRP-2 test in elderly patients before pituitary surgery. For elderly patients with non-functioning PitNET, GH response to the GHRP-2 test may support in diagnosing adrenocortical insufficiency.