GHRP-2 vs Ipamorelin: Which Secretagogue?

Key takeaways

• GHRP-2 and ipamorelin both release growth hormone (GH) through the ghrelin receptor. GHRP-2 (pralmorelin) is a six-amino-acid peptide from the 1990s Tulane research line; ipamorelin is a five-amino-acid peptide Novo Nordisk designed to release GH without the side hormones.
• Potency: in pigs, the one direct comparison, GHRP-2 worked at a lower dose and ipamorelin reached a slightly higher maximum. In people they have never been compared. GHRP-2 has far more human data, including a diagnostic test used in Japan.
• Side effects: GHRP-2 raised ACTH and cortisol in pigs and measurably increases hunger in people, by about 36% at a buffet. Ipamorelin did not raise cortisol in pigs; its effects on cortisol and appetite have not been measured in people.
• Neither has shown a benefit for muscle, fat, sleep or recovery. GHRP-2 failed a 48-week growth trial in 126 children; ipamorelin failed its one clinical trial, in bowel recovery after surgery.
• Neither can be legally compounded in the US in October 2026. The prescribable secretagogue is sermorelin.

The direct answer: ipamorelin is the more selective secretagogue on paper and GHRP-2 is the better-studied one, with the hunger and cortisol effects that come with it. Neither has a trial showing a result a user would notice, and neither is legal to compound in the United States. Our GHRP-2 and GHRP-6 profile covers GHRP-2 in full, the GHRP-6 dosage article covers its older sibling, and the CJC-1295 and ipamorelin profile covers ipamorelin.

Side by side

Potency: which releases more growth hormone

The only head-to-head data come from the paper that introduced ipamorelin. In conscious pigs, GHRP-2 reached half its maximal GH effect at 0.6 nmol/kg against 2.3 nmol/kg for ipamorelin, so it was more potent per dose; but its maximal peak was lower, 56 versus 65 ng/mL (Raun 1998). Potency and maximum point in opposite directions, and the gap in each is modest.

In people, the two have never met. GHRP-2's human record is large because it became a diagnostic drug: in 77 healthy adults in a Japanese multicenter study, a single 100 mcg intravenous dose produced a mean GH peak of 84.6 mcg/L within an hour, against 1.36 in adults with severe GH deficiency (Chihara 2007). Ipamorelin's human record is one pharmacokinetic study: 40 healthy men, eight per dose, received 15-minute infusions of 4.2 to 140 nmol/kg (roughly 3 to 100 mcg/kg); every dose produced a single GH pulse peaking at about 40 minutes, with a half-life of about two hours (Gobburu 1999). That abstract reports a modeled response rather than peak GH by dose, so the two cannot be laid side by side.

The bigger point is that the size of the pulse has not predicted results. Twice-daily nasal GHRP-2 raised GH in 126 GH-deficient children for 48 weeks and did not change growth or IGF-1 compared with placebo (Tanaka 2014). Only continuous pump delivery of GHRP-2 raised IGF-1 to a sustained plateau, in a 30-day study of healthy older adults (Bowers 2004).

Side effects: hunger and cortisol

This is the real difference, and the reason ipamorelin exists.

GHRP-2 raises hunger, measurably. Seven lean men given GHRP-2 under the skin at 1 mcg/kg per hour for 270 minutes ate 35.9% more at a buffet than on saline, every one of them more, with no change in what kinds of food they chose (Laferrère 2005). For anyone using a secretagogue to lose fat, that works against the goal.

GHRP-2 raises cortisol; ipamorelin did not, in pigs. In the same pig study, GHRP-2 and GHRP-6 raised ACTH and cortisol, while ipamorelin did not, even at doses more than 200 times its half-maximal GH dose; none of the peptides changed prolactin, thyroid or reproductive hormones in pigs (Raun 1998). The ipamorelin human study measured GH only (Gobburu 1999), so its selectivity has never been confirmed in a person.

Neither has a long safety record. Ipamorelin's one trial, in 117 adults after bowel surgery, gave 0.03 mg/kg intravenously twice daily for up to seven days; it did not speed recovery (median 25.3 versus 32.6 hours to a tolerated meal, p = 0.15), and adverse events occurred in 87.5% on ipamorelin and 94.8% on placebo (Beck 2014). FDA's Category 2 entries flag both peptides: for GHRP-2, immunogenicity and serious adverse events including deaths among critically ill study subjects and pancreatitis, without established causality; for ipamorelin, serious adverse events including a death in an intravenous gastric-motility study, and a lack of safety data for other routes (FDA Category 2 page). Neither statement shows the drug caused a death; both show how little safety data exists.

Legal status

The paths differ and the destination is the same: no 503A pharmacy and no 503B outsourcing facility may legally make either one, and a prescription does not change that (FDA Category 2 page). Our legal tracker has the committee record and the 2026 warning letters to research-peptide sellers.

Which one, then?

By evidence, GHRP-2 wins: it has real human data and a medical use. By side-effect profile, ipamorelin looks better, on the strength of pig data. By legality, it is a tie at zero. For most readers the useful answer is a third option.

• If you want a supervised rise in GH: sermorelin, a GHRH analog with human trials and an FDA approval history that a licensed pharmacy can compound, at roughly $150 to $400 a month (peptide therapy cost). It acts on a different receptor and does not stimulate hunger.
• If you suspect GH deficiency: see an endocrinologist for a stimulation test. A confirmed diagnosis opens the door to approved growth hormone.
• If you were weighing a GHRP for appetite or bulking: the hunger from GHRP-2 is real, but it comes in an unverified research vial with cortisol attached.

Our hexarelin vs ipamorelin comparison covers the other common pairing, and the best HGH peptides ranking puts the whole class in order. Our reconstitution calculator is for medications dispensed with a labeled concentration, not for research vials.

Bottom line

GHRP-2 versus ipamorelin is a choice between a well-studied GH releaser that makes you hungry and raises cortisol, and a cleaner one whose cleanliness has been shown in pigs and whose human record is one pharmacokinetic study and one failed surgical trial. GHRP-2's best result is a diagnostic test; its treatment trials did not pan out. Neither can be legally compounded in the United States, which makes sermorelin the realistic answer to "which secretagogue?"

Frequently asked questions

+−Is GHRP-2 stronger than ipamorelin?

In pigs, the only species in which they were tested side by side, GHRP-2 was more potent per dose (it worked at a lower dose) but produced a slightly smaller maximum growth hormone peak than ipamorelin. In people, they have never been compared in the same study. GHRP-2's human data are much larger: a 100 mcg intravenous dose is a standard diagnostic test in Japan. Ipamorelin's human data are one pharmacokinetic study in 40 men.

+−Which has fewer side effects, GHRP-2 or ipamorelin?

On paper, ipamorelin. GHRP-2 raised ACTH and cortisol in pigs and is known in people to increase hunger and food intake. Ipamorelin did not raise ACTH or cortisol in pigs even at very high doses. But ipamorelin's selectivity has never been confirmed in people at the doses clinics sell, and neither has long-term safety data.

+−Does GHRP-2 make you hungrier than ipamorelin?

GHRP-2's hunger effect is measured: healthy men infused with it ate about 36 percent more at a buffet, and the effect grew with the dose. Ipamorelin's effect on appetite has never been measured in people. Both act on the ghrelin receptor, the hunger hormone's receptor, so assuming ipamorelin has no hunger effect would go beyond the evidence.

+−Does ipamorelin target belly fat?

No study shows it. Ipamorelin has never been tested for body composition in people; its only clinical trial was in bowel recovery after surgery, where it did not beat placebo. GHRP-2 has not been tested for belly fat either. The GH-related peptide with real visceral-fat data is tesamorelin, brand Egrifta, which acts on a different receptor and cannot be compounded.

+−Can you stack GHRP-2 and ipamorelin?

No study has tested the combination. Both act on the same ghrelin receptor, so stacking them adds exposure without a new mechanism. The combination with real human physiology behind it is a ghrelin-receptor peptide plus a GHRH analog, which release growth hormone synergistically. Neither GHRP-2 nor ipamorelin can be legally compounded in the US, so any stack means unverified research vials.

+−Are GHRP-2 and ipamorelin legal?

Neither can be legally compounded or sold for human use in the United States in October 2026. GHRP-2 is in Category 3 for 503A pharmacies and on the Category 2 safety list for outsourcing facilities. Ipamorelin was placed in Category 2 in 2023, FDA's advisory committee voted against it in October 2024 (0 yes, 12 no, 1 abstention), and it remains in Category 2 for outsourcing facilities.

+−What is the best growth hormone releasing peptide?

Between these two, neither, because neither has a legal US source or an outcome trial showing benefit. The prescribable option is sermorelin, a GHRH analog with an FDA approval history that a licensed pharmacy can compound. If the question is body composition with measured visceral fat, tesamorelin (Egrifta) has the trial data.

Sources

1. StudyRaun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998;139:552-61. (1998)
2. StudyGobburu JV et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res 1999;16:1412-6. (1999)
3. StudyBowers CY et al. Sustained elevation of pulsatile growth hormone (GH) secretion and IGF-I, IGFBP-3 and IGFBP-5 concentrations during 30-day continuous subcutaneous infusion of GH-releasing peptide-2 in older men and women. J Clin Endocrinol Metab 2004;89:2290-300. (2004)
4. StudyLaferrère B et al. Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men. J Clin Endocrinol Metab 2005;90:611-4. (2005)
5. StudyChihara K et al.; KP-102 Study Group. A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiency. Eur J Endocrinol 2007;157:19-27. (2007)
6. StudyBeck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis 2014;29:1527-34. (2014)
7. StudyTanaka T et al. Increased secretion of endogenous GH after treatment with an intranasal GH-releasing peptide-2 spray does not promote growth in short children with GH deficiency. Clin Pediatr Endocrinol 2014;23:107-14. (2014)
8. RegulatoryFDA. Certain bulk drug substances for use in compounding may present significant safety risks (Category 2 lists for 503A and 503B and nominated-but-withdrawn substances; content current as of April 22, 2026). (2026)