GHRP-2 (Pralmorelin): The Only Approved GH Secretagogue

GHRP-2, known by its drug name pralmorelin, is a synthetic six-amino-acid peptide that stimulates the pituitary gland to release growth hormone. Its sequence is D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, its molecular weight is roughly 818, and it carries the development codes KP-102 and GPA-748 from its pharmaceutical history.

GHRP-2 comes directly from the foundational work of the American endocrinologist Cyril Y. Bowers, who first identified the growth hormone-releasing peptide class at Tulane University. After Bowers and colleagues described GHRP-6, structure-activity optimisation of that scaffold, including substituting D-2-naphthylalanine at the second position, produced GHRP-2 with substantially greater growth hormone-releasing potency. Within the classical peptide secretagogues, GHRP-2 is generally ranked second in potency behind hexarelin and ahead of GHRP-6, and it is the most clinically studied of the group.

How GHRP-2 fits among the wider family of growth hormone secretagogues, including the GHRH analogues and the non-peptide oral agents, is mapped out on our growth hormone secretagogues hub.

Where GHRP-2 came from

GHRP-2 is a product of the field Cyril Bowers opened in the 1980s, when he found that certain small peptides derived from enkephalin unexpectedly triggered growth hormone release. That discovery created the entire growth hormone-releasing peptide concept on which this whole class rests. GHRP-2 was one of the compounds that came out of systematically improving on the original scaffold, and of every peptide in the family it was carried furthest toward the clinic, passing through successive corporate owners reflected in its two development codes. Where most research peptides never leave the laboratory, GHRP-2 reached a genuine regulatory approval, even if only for a narrow diagnostic use.

The bottom line: GHRP-2 is a Bowers-derived hexapeptide ghrelin mimetic, the second most potent classical GHRP and the most heavily studied in the class.

GHRP-2 is the only growth hormone secretagogue approved by any national regulator anywhere in the world. Japan’s Pharmaceuticals and Medical Devices Agency cleared it in October 2004, marketed by Kaken Pharmaceutical under the name GHRP Kaken, and that approval has no equal among the other GHRPs.

The crucial detail, almost always glossed over by vendor pages, is what it was approved for. The Japanese approval is as a diagnostic agent, given as a single injection to assess growth hormone deficiency in adults and in children over four years of age. It is not a treatment. The test works because a single pralmorelin dose markedly raises growth hormone in healthy people but produces a blunted response in those who are deficient. Analysis of the trial data set a diagnostic threshold: a peak growth hormone of 15.0 micrograms per litre distinguishes growth hormone-deficient patients from healthy controls.

The clinical appeal of the test is easy to see once you know what it replaced. The long-standing reference method for confirming growth hormone deficiency, the insulin tolerance test, works by deliberately driving a patient into hypoglycaemia, which is unpleasant and not free of risk. A single pralmorelin injection with growth hormone measured at set time points offered a simpler, better-tolerated way to provoke the same diagnostic answer. That practical advantage, rather than any treatment benefit, is what the Japanese approval rewarded.

The bottom line: GHRP-2 is the only nationally approved GH secretagogue, but that Japanese approval covers a single diagnostic test, not ongoing treatment.

GHRP-2 mimics ghrelin, binding the growth hormone secretagogue receptor (GHS-R1a) on pituitary somatotroph cells to drive a sharp pulse of growth hormone while briefly easing the brake that somatostatin normally applies. It releases growth hormone irrespective of the subject’s sex, age or body weight, which is exactly what makes it useful as a diagnostic.

Because GHRP-2 and growth hormone-releasing hormone act through different receptors that both feed into the pituitary, combining a GHRP with a GHRH analogue such as CJC-1295 produces a larger growth hormone pulse than either compound alone, which is why that pairing is so often discussed. The trade-off is that GHRP-2 is not a clean signal: through the same ghrelin pathway it stimulates appetite and raises ACTH, cortisol and prolactin. These off-target effects are milder than with GHRP-6 but more pronounced than with the selective peptide ipamorelin.

The bottom line: GHRP-2 is a ghrelin-receptor agonist that reliably releases growth hormone but also drives appetite, cortisol and prolactin as side effects.

GHRP-2 reliably raises growth hormone in short-term testing, which is why Japan uses it diagnostically, but no trial has ever shown a long-term therapeutic benefit. It is one of the better-evidenced peptides in the secretagogue world, and that evidence still mostly stops at the diagnostic finding.

Claim	Evidence tier	Where it comes from
Diagnoses GH deficiency	Human clinical (approved)	Japanese registration trials
Raises growth hormone	Human clinical	Adult and pediatric dose studies
Reverses GH deficiency long term	Not demonstrated	Animal model showed failure
Builds muscle or burns fat	Not demonstrated	No controlled human trials

Diagnostic validation

The strongest evidence behind GHRP-2 is the work that earned its Japanese approval. Across the registration studies a single pralmorelin injection produced a sharp growth hormone rise within 15 to 30 minutes in healthy subjects, and a clearly weaker response in deficient patients, with the 15.0 micrograms per litre cut-off separating the two groups. Its diagnostic accuracy was competitive with other growth hormone provocation tests, and a 1997 pediatric study showed that even small intranasal doses produced measurable growth hormone elevation in children. This is regulator-grade clinical evidence for one specific, narrow use.

The therapeutic gap

The reason GHRP-2 never became a treatment is more interesting than simple commercial neglect. A 2005 study in the growth hormone-releasing-hormone knockout mouse, a model of severe growth hormone deficiency, found that long-term GHRP-2 failed to reverse the deficiency and actually worsened the animals’ body composition. Because GHRP-2 needs a functioning growth hormone-releasing-hormone system to work properly, it is poorly suited to the very deficiency states a therapy would target. Add the unavoidable cortisol and ACTH elevation seen in the human trials, and the case for chronic therapeutic use collapses.

The bottom line: GHRP-2 has solid human evidence for diagnosing growth hormone deficiency and essentially none for the performance and longevity uses it is marketed for.

GHRP-2 is approved only in Japan and only as a diagnostic; everywhere else it is unapproved or restricted. Its global status is unusually split for a research peptide.

Jurisdiction	Status
Japan (PMDA)	Approved as a diagnostic agent for GH deficiency
United States (FDA)	Not approved; compounding restricted (see below)
United Kingdom (MHRA)	Unlicensed medicine; not approved for human use
Australia (TGA)	Pralmorelin is Schedule 4 prescription-only
Sport (WADA)	Prohibited at all times under section S2

The United States picture is more nuanced than a simple “banned” label. GHRP-2 is not FDA-approved for any indication, and the agency has issued warning letters to pharmacies marketing it for human use. In the compounding system its standing is genuinely mixed: on the interim 503A bulks list it sits in the category for substances the FDA lacks sufficient information to evaluate, while on the interim 503B list it was placed in the favourable category only for non-injectable and non-nasal routes. The meaning of those categories, and why a peptide can land in different ones, is explained in our guide to FDA Category 1 versus Category 2. Because peptide classification is an active and shifting area, we track changes in our peptide reclassification tracker.

The practical catch is the route. The more favourable compounding category GHRP-2 landed in applies only to non-injectable, non-nasal preparations, which are not the forms anyone actually wants it in, and the FDA’s enforcement attention has fallen squarely on injectable peptide marketing. So a compound that can look partly permitted on paper is, for the injectable use people are really asking about, effectively off the table through legitimate US channels. The gap between how GHRP-2 reads on a list and how it can lawfully be supplied is a good example of why these category labels need reading carefully rather than at face value.

In sport, the World Anti-Doping Agency names pralmorelin (GHRP-2) directly among the growth hormone-releasing peptides in section S2, prohibited at all times for athletes under the Code. For how each country treats compounds like this one, see our peptide-legality guides for the US, UK and Australia.

The bottom line: Japan approves GHRP-2 as a diagnostic, the US treats it as unapproved with restricted compounding, and it is banned in sport.

GHRP-2’s main documented drawbacks are elevated cortisol, ACTH and prolactin, plus appetite stimulation, and its long-term safety has never been established. The diagnostic approval covers a single dose, so even the regulator-grade data say nothing about repeated use.

The cortisol and ACTH elevation is not a fringe concern; it is the documented finding from the Japanese trials and the specific reason the compound was judged unsuitable as a long-term therapy. Comparative work showed GHRP-2 producing a growth hormone response similar to a standard ACTH test but with greater cortisol elevation. Layer appetite stimulation on top, and the side-effect profile is real even if individually manageable at diagnostic doses.

The reason a growth hormone releaser also moves cortisol is that the ghrelin receptor it activates is not confined to the growth hormone system. Ghrelin-receptor signalling also feeds into the hypothalamic-pituitary-adrenal axis, the chain that ends in cortisol release, so a strong push on that receptor tends to drag ACTH and cortisol upward alongside growth hormone. With GHRP-2 this is not a quirk seen only at extreme exposure; it appeared in the controlled human work at the very levels used to provoke a diagnostic response. For a one-off test that is tolerable. For anything resembling repeated use it is precisely the kind of background hormonal disturbance that makes endocrinologists cautious.

A fair safety discussion also has to look at the receptor class rather than GHRP-2 in isolation, because GHRP-2’s own long-term data simply do not exist. Anamorelin, a different but related ghrelin-receptor agonist approved in Japan for cancer-related wasting, carries documented warnings for QT-interval prolongation, and published case reports describe fatal arrhythmias associated with it. That is not direct evidence against GHRP-2, but it is a real signal about what sustained ghrelin-receptor activation can do to cardiac conduction, and it is a more honest caution than the reassurance most vendor pages offer.

Finally, there is the supply problem common to all unapproved peptides. Material sold for “research use only” has not been assessed for safety, quality or purity, and regulators including the TGA have repeatedly warned that such products may not be what their labels claim. Understanding what an independent analysis can and cannot confirm is covered in our guide on how to read a certificate of analysis.

The bottom line: The known risks of GHRP-2 are hormonal and appetite-related, while its long-term safety is unknown and the ghrelin-receptor class it belongs to has a documented cardiac-conduction caution.

GHRP-2 sits in the middle of the growth hormone-releasing peptides: stronger than ipamorelin on raw growth hormone output, cleaner than GHRP-6 on appetite and cortisol, but less potent than hexarelin. Each related compound has its own detailed profile.

• Hexarelin is the most potent classical GHRP and the only one that also targets the heart’s CD36 receptor, but it loses effect with continuous use.
• GHRP-6 is the original scaffold GHRP-2 was optimised from, notable for a much stronger hunger response.
• Ipamorelin is the selective pentapeptide that releases growth hormone with minimal cortisol or prolactin, the cleaner alternative to GHRP-2.
• MK-677 (ibutamoren) is a non-peptide oral ghrelin-receptor agonist that hits the same receptor without injection, and is not a peptide at all.

The bottom line: GHRP-2 is the balanced, best-evidenced member of the GHRP family, trading some of ipamorelin’s selectivity for stronger growth hormone output.

Is GHRP-2 FDA approved?

No. GHRP-2 has never been approved by the FDA for any indication, and the agency has issued warning letters to pharmacies marketing it for human use. It is approved only in Japan, as a diagnostic agent.

What is pralmorelin used for?

Pralmorelin, the drug name for GHRP-2, is approved in Japan as a single-injection diagnostic test for growth hormone deficiency in adults and children over four, not as a treatment.

Is GHRP-2 legal?

GHRP-2 is unapproved in the US, an unlicensed medicine in the UK, and a Schedule 4 prescription-only substance in Australia, and it is banned in all WADA-governed sport at all times.

Is GHRP-2 the same as ipamorelin?

No. Both activate the ghrelin receptor, but GHRP-2 produces stronger growth hormone release alongside cortisol and prolactin elevation, while ipamorelin is more selective with minimal off-target hormonal effects.

Does GHRP-2 build muscle?

No controlled human trial has tested GHRP-2 for muscle growth or fat loss; its proven use is diagnostic, and an animal model of growth hormone deficiency showed it worsened rather than improved body composition.

What is the GHRP-2 stimulation test?

It is the diagnostic procedure approved in Japan: a single pralmorelin injection followed by timed growth hormone measurements, used to confirm or rule out growth hormone deficiency rather than to treat it.

Why was GHRP-2 never approved in the United States?

No company took it through US trials after the diagnostic approval abroad, and its cortisol elevation plus an animal study suggesting it could worsen the very deficiency it was meant to treat undermined any therapeutic case.