GHRP-2, also known as pralmorelin, is a synthetic ghrelin receptor agonist built as a successor to GHRP-6. Among the classic GHRPs it is the one that reached clinical practice: in Japan it was validated as a diagnostic test for growth hormone deficiency in adults. This is a reference article for research use, not medical advice.
What the molecule is
GHRP-2 belongs to the second generation of growth hormone releasing peptides. Like GHRP-6, it activates the GHS-R1a receptor in the pituitary and hypothalamus, the same one natural ghrelin uses. Activation produces a pulse of growth hormone: somatotrophs release their store while inhibitory somatostatin partially steps back. Japanese clinical literature lists the molecule under the code KP-102, and its international nonproprietary name is pralmorelin.
The only GHRP that became a diagnostic tool
The standard test for adult growth hormone deficiency, insulin-induced hypoglycemia, is contraindicated for some patients, so endocrinologists had long looked for a replacement. The validation study by Chihara and colleagues (European Journal of Endocrinology, 2007) tested GHRP-2 in 77 healthy volunteers and 58 patients with confirmed deficiency. The growth hormone peak arrived within an hour in every participant, and the groups separated by more than 60-fold: a mean peak of 84.6 µg/l in healthy subjects against 1.36 µg/l in patients. A 15 µg/l cut-off matched the diagnostic value of the classic insulin test, and the authors rated the reproducibility of repeated tests as favourable. That made GHRP-2 the one member of its class working in routine clinical practice, if in a narrow diagnostic role.
Potency versus amplitude
In Raun's comparative work (1998), in a swine model GHRP-2 came out more potent than GHRP-6, acting at lower molar doses, but its maximal growth hormone release was lower. The same paper recorded a trait the two molecules share: a rise in ACTH and cortisol that ipamorelin did not produce. For research purposes this is the main fork: GHRP-2 wins on potency and clinical validation, ipamorelin on profile cleanliness, GHRP-6 on the depth of its historical record.
Appetite was measured directly
The ghrelin receptor is the hunger receptor, and for GHRP-2 the effect was shown quantitatively. In the study by Laferrère and colleagues (2005), healthy men eating from a buffet consumed 35.9% more during a subcutaneous GHRP-2 infusion than during saline, with intake rising in every single participant. The authors compare the effect directly to ghrelin and propose GHRP-2 as a tool for studying eating behavior. For other models it is, on the contrary, a variable the design has to absorb.
GHRP-2 or GHRP-6
If the research question hinges on stimulus strength per unit of compound or on comparability with clinical data, the arguments favor GHRP-2. If it needs maximal release amplitude or direct continuity with forty years of literature, GHRP-6 is the reference. The full in-class comparison table lives in GHRP-2, GHRP-6, ipamorelin and CJC-1295, and the long-acting GHRH analog has its own CJC-1295 with DAC review.
Dosing in studies
Doses and routes in the clinical work varied with the task, from a diagnostic bolus to prolonged infusions, so we do not retell them here. The extract from the publications is collected on the reference page GHRP-2: reference dosing outline.
Purity and lot verification
A peptide used as a diagnostic standard sets a high bar for identity, and a research batch does not get to lower it. Longeva sends batch samples to independent third-party laboratories itself; batches are accompanied by certificates of analysis with HPLC purity and mass spectrometry confirmation, published in the open COA archive. The record for a specific lot can be reached from the GHRP-2 product page.
Summary
GHRP-2 is the most clinical peptide of its class: a validated diagnostic test, a measured effect on appetite, and a clearly mapped place between the potent GHRP-6 and the selective ipamorelin. Which of the three fits is decided by the research question, not the label.
This article is informational. In our catalog GHRP-2 is supplied strictly for laboratory research use and is not a medicine; the diagnostic use of pralmorelin refers to registered products in specific jurisdictions, not to research reagents. The full reference list with links is in the GHRP-2 monograph.
