Investigation of the clinical significance of the growth hormone-releasing peptide-2 test for the diagnosis of secondary adrenal failure.
Arimura. Hiroshi H; Hashiguchi. Hiroshi H; Yamamoto. Kiyoaki K; Shinnakasu. Atsushi A; Arimura. Aiko A; Kikuchi. Akira A; Deguchi. Takahisa T; Habu. Mika M; Fujio. Singo S; Arita. Kazunori K; Nishio. Yoshihiko Y
Key Findings
- Patients with pituitary disorders had a blunted ACTH response to GHRP‑2 compared to hypothalamic disorders and healthy controls.
- Peak cortisol after GHRP‑2 was lower in both hypothalamic and pituitary disease groups versus controls.
- A cortisol cut‑off of 11.6 µg/dL gave 88.9% specificity and 89.7% sensitivity for detecting secondary adrenal failure.
- ACTH and cortisol responses to GHRP‑2 did not correlate with CRH test results, suggesting a different stimulation pathway.
Practical Outcomes
- For biohackers using GHRP‑2 to boost growth hormone, be aware it also stimulates the HPA axis and can raise cortisol, which may affect stress, sleep, and metabolism. The test isn’t a performance enhancer per se, but the data suggest monitoring cortisol if you’re using GHRP‑2 long‑term. It also hints that GHRP‑2 could be explored as a diagnostic tool for adrenal issues, though it’s not a replacement for the gold‑standard insulin tolerance test.
Summary
The study shows that giving the peptide GHRP‑2 can trigger the pituitary to release ACTH and raise cortisol levels, and that measuring this response can help diagnose secondary adrenal insufficiency with about 89% accuracy, similar to other hormone tests.
Abstract
The aim of this study was to evaluate the ability of the growth hormone-releasing peptide-2 (GHRP-2) test to clinically diagnose hypothalamo-pituitary-adrenal (HPA) axis failure. We performed an insulin tolerance test (ITT), CRH stimulation test, and GHRP-2 test on 47 patients suspected of having a hypothalamo-pituitary disorder. Patients with pituitary disorders had significantly lower ACTH responses to the GHRP-2 test compared to patients with hypothalamic disorders and the control group. In contrast, peak cortisol levels in response to the GHRP-2 test were significantly lower in both hypothalamic and pituitary disorder cases compared with the control group. Assignment of a cut-off value of 11.6 μg/dL for the peak serum cortisol level demonstrated that the GHRP-2 test was able to predict secondary hypoadrenalism with 88.9% specificity and 89.7% sensitivity. The responses of ACTH and cortisol to the GHRP-2 test had no correlation to the CRH test, suggesting the involvement of a different mechanism of ACTH secretion. These results indicate that the GHRP-2 test may induce ACTH secretion from the pituitary gland through direct stimulation. Although the GHRP-2 test does not have the same predictive value as the insulin tolerance test (ITT), it has similar diagnostic potential as the CRH stimulation test for evaluating HPA axis failure.
Study Information
pubmed
2016
2016-03-26T00:00:00.000Z
10.1507/endocrj.ej15-0587