Head-to-Head Comparison of GHRP-2 and Hexarelin for Growth Hormone Release in Humans | Research

The takeaway

GHRP-2 and hexarelin both potently stimulate GH release in humans with slight effects on prolactin, ACTH, and cortisol — their first direct head-to-head comparison.

First head-to-head comparison
GHRP-2 and hexarelin were directly compared for the first time in humans for GH and multiple other hormone effects

What the researchers found

GHRP-2 and hexarelin both showed potent GH-releasing activity with slight stimulatory effects on prolactin, ACTH, and cortisol; their GH-releasing activities were directly compared for the first time.

Why it matters

This head-to-head comparison helps clinicians and researchers choose between the two most popular GHRPs and understand their hormonal side effect profiles.

How the study worked

Randomized clinical trial comparing GHRP-2, hexarelin, GHRH, TRH, and CRH administration in healthy men, measuring GH, prolactin, ACTH, and cortisol responses.

What this study cannot tell us

Acute single-dose study in healthy men only. No women included. Long-term effects and functional outcomes not assessed.

How to read the evidence

Strong evidence from a randomized clinical trial with multiple comparators. Comprehensive hormonal profiling provides clinically useful data.

When this study was published

Published in 1997, this remains a key reference for comparing GHRP-2 and hexarelin hormonal profiles.

The bigger picture

This comparative study helped establish the relative positioning of different GHRPs and inform clinical decision-making about which secretagogue to use.

Questions still open

Which GHRP has the best GH-specificity with fewest off-target hormonal effects?
Do the prolactin and cortisol effects of GHRPs diminish with chronic use?

Common questions

Which is better — GHRP-2 or hexarelin?

Both are potent GH releasers. This study provided their first direct comparison. GHRP-2 tends to be slightly more potent based on other studies, but both have similar hormonal profiles with slight prolactin and cortisol stimulation alongside GH release.

Why do GHRPs also affect prolactin and cortisol?

GHRP receptors are not exclusively on GH-producing cells. They're also present on cells that produce prolactin and ACTH (which drives cortisol). The effects on these hormones are typically mild compared to the GH response, but they're important to monitor.

Read the original research

Effects of GHRP-2 and hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH and cortisol levels in man. Comparison with the effects of GHRH, TRH and hCRH.

Peptides, 18(6), 885-91

View on PubMed ↗

Citation

Arvat, E; di Vito, L; Maccagno, B; Broglio, F; Boghen, M F; Deghenghi, R; Camanni, F; Ghigo, E. (1997). Effects of GHRP-2 and hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH and cortisol levels in man. Comparison with the effects of GHRH, TRH and hCRH.. Peptides, 18(6), 885-91.