Maple Ipamorelin is a synthetic pentapeptide growth hormone secretagogue (GHS) that acts as an agonist at the ghrelin receptor (GHS-R1a). It is distinguished from other GHS compounds by its selective stimulation of growth hormone (GH) release without significantly affecting adrenocorticotropic hormone (ACTH), cortisol, prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), or thyroid-stimulating hormone (TSH) levels, a selectivity profile described in its seminal characterization as unique among GHRP-receptor agonists.
For research purposes only. Not for human consumption. Not for diagnostic or therapeutic use.
Molecular Profile
Ipamorelin has the amino acid sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2, where Aib is alpha-aminoisobutyric acid and D-2-Nal is D-2-naphthylalanine. Its molecular formula is C38H49N9O5 with a molecular weight of approximately 711.85 Da and CAS number 170851-70-4. The peptide was developed at Novo Nordisk A/S through a systematic structure-activity program that identified it within a series of compounds lacking the central Ala-Trp dipeptide of growth hormone-releasing peptide-1 (GHRP-1).
The structural modifications that distinguish ipamorelin from earlier GHS compounds, particularly the incorporation of non-natural amino acids and D-amino acids, confer both its selectivity profile and its resistance to enzymatic degradation.
Primary Research Mechanisms
Growth Hormone Release Selectivity
The defining pharmacological property of ipamorelin is its selective stimulation of GH secretion. According to the foundational characterization by Raun et al. (1998) in the European Journal of Endocrinology (DOI: 10.1530/eje.0.1390552), ipamorelin was designated “the first selective growth hormone secretagogue.” In conscious swine, ipamorelin released GH with an ED50 of 2.3 nmol/kg and an Emax of 65 ng GH/mL plasma, comparable to GHRP-6 (ED50 = 3.9 nmol/kg, Emax = 74 ng GH/mL).
The critical distinction emerged in hormonal profiling: while both GHRP-6 and GHRP-2 administration resulted in increased plasma levels of ACTH and cortisol, ipamorelin did not elevate ACTH or cortisol to levels significantly different from those observed with growth hormone-releasing hormone (GHRH) stimulation. This lack of ACTH/cortisol stimulation persisted even at doses more than 200-fold higher than the ED50 for GH release, indicating that the selectivity is not dose-dependent but represents a fundamental mechanistic difference.
Ghrelin Receptor (GHS-R1a) Agonism
Ipamorelin acts through the growth hormone secretagogue receptor type 1a (GHS-R1a), the same receptor bound by the endogenous hormone ghrelin. Pharmacological profiling using GHRP and GHRH antagonists confirmed that ipamorelin stimulates GH release via a GHRP-like receptor mechanism rather than through the GHRH receptor pathway. In primary rat pituitary cells, ipamorelin released GH with a potency (EC50 = 1.3 nmol/L) and efficacy (Emax = 85%) similar to GHRP-6 (EC50 = 2.2 nmol/L, Emax = 100%).
Research by Ahnfelt-Ronne et al. (2001) at Novo Nordisk (DOI: 10.1385/ENDO:14:1:133) demonstrated that GHS compounds including those derived from the ipamorelin series accumulate substantially in the glandular part of the stomach, the site of ghrelin synthesis. Their finding that gastrointestinal tract resection attenuated GHRP-6-induced GH secretion by 60-70% suggests that endogenous ghrelin may mediate part of the GH-releasing effect of exogenous GHS compounds, adding complexity to the pharmacology of this receptor system.
Gastrointestinal Motility Effects
Beyond GH secretion, ipamorelin’s activity at the ghrelin receptor produces effects on gastrointestinal function. Venkova et al. (2009) at the University of Oklahoma (DOI: 10.1124/jpet.108.149211) investigated ipamorelin in a rodent model of postoperative ileus (POI). A single dose of ipamorelin (1 mg/kg) decreased the time to first bowel movement following surgical manipulation. Repetitive dosing (0.1 or 1 mg/kg, four doses daily at 3-hour intervals over 2 days) significantly increased cumulative fecal pellet output, food intake, and body weight gain compared to vehicle. These prokinetic effects are consistent with ghrelin receptor activation in the gastrointestinal tract and represent a distinct research application for ipamorelin beyond growth hormone pharmacology.
Comparison with Other Growth Hormone Secretagogues
The GHS class includes several peptidic compounds (GHRP-1, GHRP-2, GHRP-6, hexarelin) and peptidomimetic derivatives (MK-677/ibutamoren). Ipamorelin’s position within this class is defined by its selectivity. While GHRP-2 demonstrates higher GH-releasing potency than ipamorelin (ED50 = 0.6 nmol/kg vs 2.3 nmol/kg in swine), GHRP-2 also stimulates ACTH and cortisol release. GHRP-6 shows similar GH potency to ipamorelin but likewise elevates ACTH and cortisol. Ipamorelin achieves a selectivity for GH release comparable to that of GHRH itself, the endogenous hypothalamic releasing factor, while acting through an entirely different receptor pathway.
For researchers studying GH axis pharmacology, this selectivity is significant because it allows investigation of GH-specific effects without the confounding influence of concurrent ACTH/cortisol axis activation, which can independently affect metabolic, inflammatory, and growth parameters.
Product Specifications
Sequence: Aib-His-D-2-Nal-D-Phe-Lys-NH2
CAS Number: 170851-70-4
Molecular Formula: C38H49N9O5
Molecular Weight: 711.85 Da
Purity: ≥99% (HPLC verified)
Form: Lyophilized powder
Storage: -20°C, desiccated, protected from light
COA: Batch-specific Certificate of Analysis by independent third-party testing (Testides Analytical)
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Frequently Asked Questions
What makes ipamorelin different from other growth hormone secretagogues?
Ipamorelin is distinguished by its selective stimulation of growth hormone release without significantly affecting ACTH, cortisol, prolactin, FSH, LH, or TSH levels. Other GHS compounds like GHRP-2 and GHRP-6 stimulate both GH and ACTH/cortisol release. Ipamorelin’s selectivity profile is comparable to that of GHRH (the endogenous hypothalamic releasing hormone) despite acting through a completely different receptor (the ghrelin receptor GHS-R1a rather than the GHRH receptor). This was documented in the original Raun et al. (1998) characterization at Novo Nordisk.
What receptor does ipamorelin act on?
Ipamorelin acts as an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), also known as the ghrelin receptor. This is the same receptor bound by the endogenous hormone ghrelin. Despite acting on the same receptor as other GHS compounds like GHRP-6 and GHRP-2, ipamorelin produces a more selective hormonal response, suggesting that different GHS-R1a agonists may activate distinct downstream signaling pathways, a concept analogous to biased agonism documented in other receptor systems.
Where can I buy ipamorelin research peptide in Canada?
Maple Research Labs supplies ipamorelin in 5mg and 10mg vial sizes. All ipamorelin is verified at 99%+ purity by Testides Analytical and ships from within Canada with same-day processing. A batch-specific Certificate of Analysis is included with every order. Ipamorelin is sold exclusively for research purposes and is not approved for human use.
What is the difference between ipamorelin and CJC-1295?
Ipamorelin and CJC-1295 act through different receptor pathways in the growth hormone axis. Ipamorelin is a ghrelin receptor (GHS-R1a) agonist that mimics the action of ghrelin at the pituitary level. CJC-1295 is a modified growth hormone-releasing hormone (GHRH) analogue that acts through the GHRH receptor. Because they operate through different receptors, they are sometimes studied in combination in preclinical research. Maple Research Labs offers both ipamorelin and CJC-1295 (with DAC), as well as a CJC-1295 + Ipamorelin blend.
Related Research
Explore related peptide research from Maple Research Labs: CJC-1295 (with DAC) | CJC-1295 (no DAC) | CJC-1295 + Ipamorelin Blend | Tesamorelin | Understanding Certificates of Analysis
For research purposes only. Not for human consumption. Not for diagnostic or therapeutic use.