What is Ipamorelin?
Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) is a pentapeptide growth hormone secretagogue with the formula C38H49N9O5 and a molar mass of 711.9 g/mol. It was developed at Novo Nordisk in Denmark in the 1990s from the GHRP-1 series, by removing a central dipeptide and building in non-natural residues that make it far more resistant to enzymes than natural peptides.
In plain terms, ipamorelin imitates ghrelin, the body's own hunger hormone, at the GHS-R1a receptor on pituitary somatotroph cells. Binding switches on a calcium signal inside the cell that releases a pulse of stored GH. Because it acts on a different receptor from GHRH, researchers often study it next to GHRH analogues such as CJC-1295, where the two signals are reported to complement each other.
What sets ipamorelin apart from GHRP-2, GHRP-6 and hexarelin is its clean hormonal profile. In the original animal pharmacology it did not change FSH, LH, prolactin or TSH, and it avoided the cortisol and ACTH rise seen with the older peptides. That selectivity is why it is often called the first selective GH secretagogue.
Benefits of Ipamorelin reported in research
Evidence level shown on each card.Potent, pulse-like growth hormone release
In rat pituitary cells, ipamorelin released GH with a potency (EC50 about 1.3 nmol/l) similar to GHRP-6. In healthy male volunteers, it produced a single, dose-dependent GH peak at roughly 40 minutes that then returned to baseline, closely resembling a natural secretory pulse.
No cortisol or ACTH spike
In conscious swine, GHRP-6 and GHRP-2 raised ACTH and cortisol, while ipamorelin did not, even at more than 200-fold its ED50 for GH release. This makes it a cleaner tool for studying GH effects without stress-hormone interference.
Supports longitudinal bone growth
In a 1999 rat study, 15 days of ipamorelin dose-dependently increased the longitudinal bone growth rate of the tibia from 42 to as much as 52 micrometres per day, alongside greater body weight gain.
Increases bone mineral content
Over 12 weeks in adult female rats, ipamorelin increased tibial and vertebral bone mineral content measured by DXA, driven by larger bone dimensions, with effects comparable to GHRP-6 and GH itself.
Promotes gut motility after surgery
Acting as a ghrelin mimetic, ipamorelin shortened the time to first bowel movement in a rat model of postoperative ileus, and repeated dosing increased fecal output, food intake and body weight gain.
What the research shows
The founding paper is Raun et al., published in the European Journal of Endocrinology in 1998. The Novo Nordisk team showed that ipamorelin released GH from primary rat pituitary cells with a potency and efficacy close to GHRP-6, worked through the GHRP receptor rather than the GHRH receptor, and in swine released GH without affecting FSH, LH, prolactin, TSH, ACTH or cortisol. The authors concluded that its selectivity for GH was similar to that of GHRH itself.
Human pharmacology followed in 1999 (Gobburu et al., Pharmaceutical Research). In a dose-escalation study with eight healthy men per dose level, ipamorelin showed dose-proportional kinetics, a terminal half-life of about 2 hours, and one discrete GH release episode peaking at about 0.67 hours at every dose. The authors built a PK/PD model describing this episodic, pulse-like response.
Skeletal research is the most consistent preclinical theme. Johansen et al. (1999) reported faster longitudinal bone growth in rats, and Svensson et al. (2000, Journal of Endocrinology) found that 12 weeks of ipamorelin increased bone mineral content in adult female rats through increased bone size, while volumetric bone density stayed unchanged.
Ipamorelin was also developed for gut motility. In rats after abdominal surgery it accelerated recovery of bowel function (Venkova et al., 2009). A phase 2 trial in 114 bowel-resection patients found it well tolerated, with a median time to first tolerated meal of 25.3 hours versus 32.6 hours on placebo, but that difference did not reach statistical significance (Beck et al., 2014).
Ipamorelin - frequently asked questions
What is ipamorelin?
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Ipamorelin is a synthetic pentapeptide that mimics ghrelin at the GHS-R1a receptor and stimulates the pituitary to release growth hormone. It was developed by Novo Nordisk and described in 1998 as the first selective growth hormone secretagogue.
What are the benefits of ipamorelin?
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Research reports potent, pulse-like GH release in humans and animals without the cortisol and ACTH rise seen with older GHRPs. Rat studies also showed faster bone growth, higher bone mineral content and improved gut motility after surgery.
Ipamorelin vs CJC-1295: what is the difference?
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Ipamorelin acts on the ghrelin receptor (GHS-R1a), while CJC-1295 is a GHRH analogue acting on the GHRH receptor. Because they use two separate pathways, researchers often study them together, which is why Cryopept also offers a CJC-1295 (no DAC) + Ipamorelin blend.
How should ipamorelin be stored?
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Lyophilized ipamorelin is best kept at -20 °C, sealed, dry and away from light, where it remains stable for long periods. Once in solution it should be refrigerated and protected from repeated freezing and thawing.
Is ipamorelin legal in the EU?
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Ipamorelin is not an authorised medicine in the EU, and growth hormone secretagogues are on the WADA prohibited list for athletes. It can be purchased in the EU as a research compound, and Cryopept supplies it for laboratory research use.
