GHRP-2 vs GHRP-6

GHRP-2 and GHRP-6 are first-generation synthetic ghrelin-receptor (GHS-R1a) agonists. GHRP-2 is the more potent GH releaser of the two; GHRP-6 is known for a stronger appetite effect, consistent with ghrelin’s role as a hunger hormone.

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GHRP-2

A synthetic hexapeptide growth-hormone-releasing peptide that acts on the ghrelin receptor and is used in some countries as a diagnostic test of GH reserve.

BEST STUDIED FOR

GH secretagogues

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GHRP-6

One of the first synthetic growth-hormone-releasing hexapeptides, a ghrelin-receptor agonist studied for GH release and as a diagnostic probe.

BEST STUDIED FOR

GH secretagogues

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SIDE BY SIDE

	GHRP-2	GHRP-6
The key difference	Stronger GH release, less appetite drive	Marked hunger signal via ghrelin receptor
Class	GH secretagogues	GH secretagogues
Mechanism	GHRP-2 (D-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH2) is a ghrelin-receptor (GHS-R1a) agonist with no structural homology to GHRH.	GHRP-6 binds the ghrelin receptor (GHS-R1a) and stimulates pituitary GH release; it was used to characterise that receptor before ghrelin itself was discovered.
Status	Used clinically in Japan as a GH-reserve stimulation test; otherwise unapproved. Detected and banned in sport.	A research and diagnostic tool from the 1990s onward; not an approved medicine. Banned in sport.
Reported safety signals	Diagnostic-test literature reports it as well tolerated in single-dose testing. It is not selective: secondary rises in cortisol and prolactin are documented across the GHRP class.	Older diagnostic studies used single doses. Class-wide, GHRPs raise cortisol/prolactin and increase hunger; there are no long-term human safety data.
A key study	A development profile of pralmorelin, a synthetic growth-hormone-releasing peptide developed by Polygen and Tulane University. (Drugs R D 2004, PMID 15230633)	Assessed GHRP-6 as a provocative test of pituitary GH reserve in the diagnosis of GH deficiency. (J Pediatr Endocrinol Metab 1996, PMID 8887178)

WHEN TO RESEARCH WHICH

GHRP-2 suits studies focused on GH output; GHRP-6 suits studies where the ghrelin-like appetite response is itself the subject. Both are discussed here strictly as research compounds; nothing on this page is medical advice or a dosing guide.

REFERENCES (PUBMED)

[GHRP-2] Pralmorelin: GHRP 2, GPA 748, growth hormone-releasing peptide 2, KP-102 D, KP-102 LN, KP-102D, KP-102LN — Drugs R D 2004. PMID 15230633
[GHRP-2] Clinical Usefulness of the Growth Hormone-Releasing Peptide-2 Test for Hypothalamic-Pituitary Disorder — J Endocr Soc 2022. PMID 35795807
[GHRP-2] Determination of growth hormone secretagogue pralmorelin (GHRP-2) and its metabolite in human urine by liquid chromatography/electrospray ionization tandem mass spectrometry — Rapid Commun Mass Spectrom 2010. PMID 20552695
[GHRP-6] Growth hormone releasing hexapeptide-6 (GHRP-6) test in the diagnosis of GH-deficiency — J Pediatr Endocrinol Metab 1996. PMID 8887178
[GHRP-6] Growth hormone-releasing peptides and their analogs — Front Neuroendocrinol 1998. PMID 9465289
[GHRP-6] Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males — Transl Androl Urol 2020. PMID 32257855

FREQUENTLY ASKED

What is the difference between GHRP-2 and GHRP-6?

What is the regulatory status of GHRP-2 and GHRP-6?

GHRP-2: Used clinically in Japan as a GH-reserve stimulation test; otherwise unapproved. Detected and banned in sport. GHRP-6: A research and diagnostic tool from the 1990s onward; not an approved medicine. Banned in sport.

What safety signals have been reported?

GHRP-2: Diagnostic-test literature reports it as well tolerated in single-dose testing. It is not selective: secondary rises in cortisol and prolactin are documented across the GHRP class. GHRP-6: Older diagnostic studies used single doses. Class-wide, GHRPs raise cortisol/prolactin and increase hunger; there are no long-term human safety data.

Which studies is this comparison based on?

For GHRP-2: “Pralmorelin: GHRP 2, GPA 748, growth hormone-releasing peptide 2, KP-102 D, KP-102 LN, KP-102D, KP-102LN” (PMID 15230633); “Clinical Usefulness of the Growth Hormone-Releasing Peptide-2 Test for Hypothalamic-Pituitary Disorder” (PMID 35795807); “Determination of growth hormone secretagogue pralmorelin (GHRP-2) and its metabolite in human urine by liquid chromatography/electrospray ionization tandem mass spectrometry” (PMID 20552695). For GHRP-6: “Growth hormone releasing hexapeptide-6 (GHRP-6) test in the diagnosis of GH-deficiency” (PMID 8887178); “Growth hormone-releasing peptides and their analogs” (PMID 9465289); “Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males” (PMID 32257855).