GHRP-2 Test Matches Insulin Tolerance Test for Diagnosing Secondary Adrenal Insufficiency
Background
Secondary adrenal insufficiency arises from deficient ACTH or CRH secretion, rather than primary adrenal failure, and can precipitate life-threatening adrenal crisis if undetected. Accurate assessment of the hypothalamic-pituitary-adrenal (HPA) axis is therefore essential both for diagnosis and for localizing the site of disease — hypothalamic versus pituitary. The insulin tolerance test (ITT) is the longstanding gold standard for evaluating HPA axis integrity in hypopituitarism, but it carries recognized disadvantages including hypoglycemia-induced risk that limits its use in many patients. Growth hormone-releasing peptide-2 (GHRP-2) acts on pituitary GHSR receptors and has been observed to stimulate ACTH release, raising the possibility that it could probe the same axis without the hazards of insulin-induced hypoglycemia.
Study Design
Patients with hypopituitarism underwent both the standard insulin tolerance test (ITT) and the GHRP-2 stimulation test to compare ACTH secretory responses. The primary endpoint was concordance of ACTH response classification — significant versus non-significant — between the two tests. No specific sample size, dosing regimen, route of administration, or assay methodology are reported in the available abstract. Both tests were applied to the same patient cohort, making each subject their own control, with ITT serving as the reference standard against which GHRP-2 performance was judged.
Results
Complete concordance in ACTH response classification was observed between the two diagnostic tests across the hypopituitary patient cohort. Patients who mounted a significant ACTH response to ITT likewise showed a significant response to the GHRP-2 test, with no exceptions reported. Conversely, patients who failed to produce a significant ACTH response to ITT also failed to respond to GHRP-2, again without exception.
Full bidirectional concordance between GHRP-2 and ITT ACTH responses was observed in every patient tested — no patient was misclassified by the GHRP-2 test relative to the ITT gold standard.
These findings held across both hypothalamic and pituitary etiologies of secondary adrenal insufficiency, indicating that the GHRP-2 test can probe the HPA axis regardless of where along the hypothalamic-pituitary axis the lesion resides. No quantitative response magnitudes, sensitivity, specificity, or p-values are reported in the available abstract.
Key Findings
- Full concordance: every patient with significant ACTH response to ITT also responded to GHRP-2
- Every patient without significant ACTH response to ITT also failed to respond to GHRP-2
- GHRP-2 test applicability confirmed across both hypothalamic and pituitary etiologies
- GHRP-2 proposed as a substitute for ITT in hypopituitarism diagnostics
Why It Matters
GHRP-2 may offer a clinically viable, lower-risk alternative to ITT for diagnosing secondary adrenal insufficiency in patients with hypopituitarism — a group in whom insulin-induced hypoglycemia carries elevated danger. Clinicians managing pituitary disease could potentially replace ITT with GHRP-2 stimulation testing, reducing procedural risk without sacrificing diagnostic accuracy, provided these findings are confirmed in larger, quantitatively powered trials. For practitioners already using GHRP-2 in hormone-replacement or diagnostics contexts, the data reinforce its HPA axis activity as a real and clinically measurable effect rather than a secondary curiosity. Full protocol standardization — including optimal dose, timing, and cut-off thresholds — will be required before GHRP-2 testing can replace ITT in formal clinical guidelines.
