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Ipamorelin
Research PeptideAlso known as: NNC 26-0161 · NNC26-0161
Animal Only
Ipamorelin's published evidence base consists of animal studies (rats, pigs, dogs, mice) and in vitro pituitary cell data. In these models, it selectively stimulates GH release without raising ACTH or cortisol, increases bone mineral content, and shows partial rescue of glucocorticoid-induced nitrogen wasting. The Lall 2001 mouse study documented a GH-independent adipogenic effect, directly contradicting the popular fat-loss claim. The body-composition, anti-aging, sleep, and wound-healing claims that drive off-label interest are not supported by animal or in vitro research specific to ipamorelin. The most commonly cited "preserves pulsatile GH release" reference (Ionescu & Frohman 2006, JCEM) is a CJC-1295 study, not an ipamorelin study, a misattribution routinely propagated in vendor marketing.
The "preserves pulsatility" source is a CJC-1295 paper
The paper most often cited online to support the claim that ipamorelin "preserves natural GH pulsatility", Ionescu M & Frohman LA, JCEM 2006 (PMID 17018654), is a study of CJC-1295, not ipamorelin. The misattribution is pervasive in vendor marketing and online blogs. The evidence for ipamorelin pulsatility is limited to animal and in vitro data. The underlying mechanism (GHS release is somatostatin-feedback-governed, unlike exogenous rhGH) is sound, but claims that ipamorelin specifically "preserves pulsatility" are extrapolations from animal models, not findings from ipamorelin-specific research.
The only published efficacy trial for ipamorelin failed its primary endpoint
Beck DE, Sweeney WB, McCarter MD (2014), a multicenter, double-blind, placebo-controlled trial in bowel-resection patients sponsored by Rhythm Pharmaceuticals, tested ipamorelin for postoperative ileus. Median time to first tolerated meal was 25.3 h (ipamorelin) vs 32.6 h (placebo), p=0.15. The primary endpoint was NOT met. No further development has been publicly announced. This is the only controlled efficacy study published for ipamorelin, and it was negative. Every marketing claim rests on animal and in vitro data or extrapolation.
For laboratory research use only. Not for human or animal consumption.
Evidence Tier
Animal Only
Mol. Weight
711.85 Da
Last Reviewed
Apr 21, 2026
Claimed benefits by evidence tier
Column header colour matches the tier
Animal Only7
- Selective for GH (does not raise cortisol/ACTH)
- Increases lean body mass / muscle
- Reduces body fat
- Increases bone mineral density / content
- Counteracts steroid/glucocorticoid-induced muscle & bone loss
- Preserves natural pulsatile GH pattern vs exogenous GH
- Treatment of GH deficiency
Anecdotal3
- Anti-aging / longevity effects
- Improves sleep quality
- Accelerates wound healing or recovery
About this peptide
Plain English
Ipamorelin is a research peptide developed in the 1990s by Novo Nordisk. It works by signaling the pituitary gland, the brain's master hormone regulator, to release a pulse of growth hormone. Unlike older peptides with a similar mechanism, ipamorelin appears to do this without substantially raising stress hormones like cortisol, which was considered an improvement when it was first described in animal studies. The many claims made about it online, fat loss, muscle gain, anti-aging, sleep improvement, are either extrapolated from animal and in vitro studies or have no formal research behind them at all.
Technical
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue (GHS) that acts as a selective agonist at the ghrelin receptor (GHS-R1a, also called the growth hormone secretagogue receptor). Upon binding GHS-R1a in pituitary somatotroph cells, it activates G-protein signaling pathways that elevate intracellular Ca²⁺ and cAMP, triggering pulsatile GH secretion. Its defining pharmacological characteristic relative to its predecessors (GHRP-2, GHRP-6) is its selectivity: at doses exceeding 200-fold the GH-release ED₅₀, ipamorelin does not stimulate significant release of adrenocorticotropic hormone (ACTH), cortisol, prolactin, FSH, LH, or TSH, in animal studies. The non-standard residues in its sequence (Aib, D-2-Nal, D-Phe) confer metabolic stability against peptidase degradation and constrain the bioactive conformation. GH-mediated downstream effects (hepatic IGF-1 production, anabolic signaling) are the proposed basis for claimed metabolic benefits, but the evidence base is limited to animal and in vitro research.
Mechanism of action
GHS-R1a agonism → pulsatile GH secretion
Ipamorelin binds and activates GHS-R1a on pituitary somatotroph cells. Receptor activation couples to Gαq proteins, elevating intracellular IP₃ and Ca²⁺, which triggers exocytosis of stored GH. The result is a discrete pulse of GH release subject to normal somatostatin-mediated negative feedback, theoretically preserving pulsatility, unlike exogenous recombinant GH which produces sustained non-physiologic serum levels.
Selectivity for GH, absence of ACTH/cortisol stimulation
In rats, pigs, and dogs, GHRP-2 and GHRP-6 at GH-stimulating doses also produced significant ACTH and cortisol elevations. Ipamorelin, even at doses 200-fold above its GH-release ED₅₀, did not raise ACTH or cortisol above levels seen with GHRH alone in these animal models. The structural basis is attributed to the D-2-Nal substitution and C-terminal amide. This selectivity has been characterized in animal studies only.
GH → IGF-1 → downstream anabolic effects
GH released by ipamorelin acts on hepatic GH receptors to induce IGF-1 production, which mediates most of the classically "anabolic" effects attributed to GH (protein synthesis, lipolysis, nitrogen retention, bone turnover). The magnitude and duration of IGF-1 elevation following ipamorelin administration is not characterised in published research beyond what has been observed in animal models.
GI motility (ghrelin-mimetic peripheral effect)
Ghrelin receptors are expressed in the gastrointestinal tract where ghrelin promotes gastric motility. As a ghrelin mimetic, ipamorelin was hypothesized to accelerate gastric emptying and GI transit based on rodent preclinical models. Controlled testing of this hypothesis in a bowel-resection context failed to show a statistically significant effect (Beck 2014, p=0.15).
All mechanistic characterization of ipamorelin, including its defining cortisol-selectivity claim, was performed in rats, pigs, and dogs. Receptor pharmacology is largely conserved across species for GHS-R1a, but dose-response relationships, receptor density, and feedback dynamics differ. Preclinical findings cannot be assumed to translate directly to other species. All post-2001 mechanistic discussion in review articles is derivative of the original Novo Nordisk-authored papers; there is no independent mechanistic replication outside the GHS class literature.
Key studies
Ipamorelin, the first selective growth hormone secretagogue (1998)
Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH · European Journal of Endocrinology 139(5):552–561
- Participants
- Rats (Sprague-Dawley), pigs, dogs; in vitro pituitary cells. No human subjects.
- Methodology
- In vitro receptor binding and pituitary cell GH release; in vivo IV/SC dose-response in rodents and large animals; comparison to GHRH, GHRP-2, GHRP-6 for GH, ACTH, and cortisol release.
- Result
- Ipamorelin was highly potent for GH release and, uniquely among GHRPs tested, did not raise ACTH or cortisol above GHRH baseline even at doses 200× the GH-release ED₅₀.
Honest read
All authors are employees of Novo Nordisk A/S, the developer of ipamorelin, a clear conflict of interest. This is an animal study; the cortisol-selectivity finding, which became the cornerstone of ipamorelin's marketing, originates entirely from animal models and has not been replicated in any independent study. The study established ipamorelin's GH selectivity profile in animals. This paper has been cited extensively in marketing materials without disclosing that it is entirely animal work from the peptide's manufacturer.
The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats (2000)
Svensson J, Lall S, Dickson SL, Bengtsson BA, Rømer J, Ahnfelt-Rønne I, Ohlsson C, Jansson JO · Journal of Endocrinology 165(3):569–577
- Participants
- Adult female Sprague-Dawley rats
- Methodology
- SC treatment with ipamorelin or GHRP-6; DXA bone mineral content and density measurements vs controls.
- Result
- Both GHS increased total BMC. Tibial area BMD increased. Total and vertebral BMD unchanged.
Honest read
Rat model, female-only. The evidence is limited to this animal model and no bone density data beyond animal studies exists for ipamorelin.
The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats (2001)
Svensson J, et al. · Journal of Bone and Mineral Research 16(12):2280–2286
- Participants
- Adult rats treated with prednisolone ± ipamorelin
- Methodology
- In vivo treatment; bone formation markers, nitrogen balance, body composition. Followed by Aagaard 2009 which extended to N-balance.
- Result
- Ipamorelin partially counteracted glucocorticoid-induced decreases in bone formation markers. Aagaard 2009 showed partial rescue of nitrogen wasting, though less effectively than exogenous GH.
Honest read
Rat study only. Prednisolone doses appropriate to rat glucocorticoid excess models; the evidence is limited to animal models and the finding should not be extrapolated beyond that context. This finding is sometimes cited to justify ipamorelin use in corticosteroid contexts, but that extrapolation is not supported by available evidence.
Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues (2001)
Lall S, Tung LY, Ohlsson C, Jansson JO, Dickson SL · Biochemical and Biophysical Research Communications 280(1):132–138
- Participants
- GH-deficient and GH-intact mice
- Methodology
- 9-week SC ipamorelin treatment; DXA body composition; fat pad weights; comparison to GH treatment.
- Result
- In GH-deficient mice, ipamorelin increased body weight by 15.3% vs 95.5% for GH. In GH-intact mice, ipamorelin increased total body fat percentage on DEXA. Relative fat pad weights increased. Weight gain occurred in BOTH GH-deficient and GH-intact mice, suggesting a GH-independent adipogenic component.
Honest read
This finding, that ipamorelin may increase body fat independent of GH action, directly contradicts the popular claim that ipamorelin causes fat loss. It is almost never mentioned in online discussions of ipamorelin. The study was conducted in mice and the finding is mechanistically plausible given ghrelin's known orexigenic and lipogenic effects. This study should be considered in any honest assessment of body composition claims.
Research timeline
- 1997
Novo Nordisk A/S medicinal chemistry program (Måløv, Denmark) identifies ipamorelin within a GHRP-1 analogue series; internal development code NNC 26-0161 assigned.
- 1998
Raun K, Hansen BS, Johansen NL et al. publish the founding characterization paper, "Ipamorelin, the first selective growth hormone secretagogue", in European Journal of Endocrinology. All seven authors are Novo Nordisk employees. Animal studies only (rats, pigs, dogs).
- 1999
Gobburu JVS et al. publish a PK/PD study (IV dose-escalation) in Pharmaceutical Research, the only published pharmacokinetic characterization of ipamorelin. Confirms GH release in an acute setting; no efficacy endpoint assessed. Novo Nordisk / SUNY Buffalo affiliation.
- 2000
Svensson J et al. publish rat BMC data in Journal of Endocrinology, showing ipamorelin increases total bone mineral content in adult female rats.
- 2001
Svensson J et al. publish rat data showing ipamorelin counteracts glucocorticoid-induced bone formation loss (JBMR). Same year, Lall S et al. document GH-INDEPENDENT ADIPOGENIC effects in GH-deficient and GH-intact mice (BBRC), a countersignal to fat-loss claims.
- 2006
Ionescu M & Frohman LA publish "Pulsatile Secretion of Growth Hormone (GH) Persists during Continuous Stimulation by CJC-1295" in JCEM. This is a CJC-1295 study, not an ipamorelin study, but the paper is frequently misattributed in ipamorelin marketing to support a "preserves natural pulsatility" claim. Recorded here for that reason.
- 2009
Aagaard NK et al. publish prednisolone N-balance rat data (Growth Horm IGF Res), showing ipamorelin counteracts accelerated nitrogen wasting though less efficiently than GH.
- 2012
Greenwood-Van Meerveld B et al. publish rodent postoperative ileus studies providing the preclinical rationale for clinical development in GI motility.
- 2014
Beck DE, Sweeney WB, McCarter MD publish a multicenter, double-blind, placebo-controlled trial in International Journal of Colorectal Disease. Primary endpoint (time to first tolerated meal) FAILED at p=0.15. No further clinical development announced. This is the only published efficacy trial of ipamorelin and it was negative.
- 2017
Sigalos JT & Pastuszak AW publish a broad GHS-class safety and efficacy review (Sex Med Rev) from Baylor College of Medicine urology. Limited ipamorelin-specific primary data; useful as class context.
- 2020
Sinha DK et al. publish narrative review on GHS (Transl Androl Urol); ipamorelin mentioned in the broader GHS class discussion but no new primary data.
- 2024
FDA Pharmacy Compounding Advisory Committee meeting (October 29, 2024), docket FDA-2024-N-4188. The committee reviewed ipamorelin acetate; FDA cited absence of a USP monograph, absence of an approved drug product, insufficient evidence of clinical need and safety, and nominator data inconsistencies between acetate and free base forms.
- 2026
WADA 2026 Prohibited List enters force (January 1, 2026). Ipamorelin explicitly named in category S2.2.4, Growth Hormone Secretagogues and their mimetics.
What we don't know
- Efficacy for any marketed indication, the evidence base is limited to animal and in vitro studies. Body composition, GH deficiency treatment, anti-aging, sleep, and wound healing claims are not supported by any published animal or in vitro research specific to ipamorelin, let alone controlled efficacy data.
- Long-term safety characterization, published safety data is limited to short-duration animal studies. No published study characterizes the safety profile at extended treatment durations.
- Subcutaneous pharmacokinetics, all published PK data (Gobburu 1999) was obtained via IV infusion in an acute setting. SC bioavailability, Tmax, Cmax, and GH response following SC injection are unpublished for any species.
- IGF-1 response magnitude and duration, whether ipamorelin-stimulated GH pulses produce sustained, meaningful IGF-1 elevation is not established in published research.
- Dose-response for any indication, all proposed protocols are extrapolated from animal studies; no published dose-response or dose-optimization data exists beyond the animal pharmacology.
- Drug interactions, no formal interaction studies. Theoretical interactions with insulin, exogenous GH, somatostatin analogues, glucocorticoids, thyroid hormone, and other GHS-R1a ligands are mechanistically plausible.
- Carcinogenesis risk, chronic IGF-1 elevation is associated with increased cancer risk in epidemiological literature; no ipamorelin-specific carcinogenicity studies exist.
- Oral / intranasal bioavailability, oral bioavailability is essentially zero (peptide-bond hydrolysis in GI tract). Intranasal delivery was studied preclinically but no bioavailability data beyond that has been published.
- The adipogenic signal from Lall 2001, whether GH-independent fat gain occurs at relevant doses is unknown. This finding potentially directly contradicts the fat-loss marketing claim.
- Cortisol selectivity beyond animal models, the cornerstone selectivity claim has been demonstrated in rats, pigs, and dogs only; no cortisol/ACTH challenge study beyond animal models exists for ipamorelin.
Stability & handling
- Lyophilized shelf life
- Up to ~24 months from manufacture at −20°C (vendor-claimed; no peer-reviewed stability study specific to ipamorelin identified)
- Lyophilized storage
- Freeze at −20°C (preferred) or 2–8°C short-term; sealed, desiccated, protected from light and moisture
- Reconstitution diluents
- Bacteriostatic water for injection (benzyl alcohol preserved; standard for multi-dose research vials), Sterile saline (0.9% NaCl), Sterile water for injection (single-use only)
- Reconstituted (refrigerated)
- ~28–40 days at 2–8°C (vendor/manufacturer guidance; no peer-reviewed analytical stability validation)
- Reconstituted (room temp)
- Degrades within hours to days; not recommended, peptide-bond hydrolysis and D-amino acid epimerization risk increases with temperature
- OK to refreeze
- No
- Light sensitive
- Yes, protect from light
Contains two D-amino acid residues (D-2-Nal, D-Phe) critical for receptor binding and metabolic stability; racemization during synthesis or storage reduces potency substantially and is not detectable by standard reverse-phase HPLC (requires chiral HPLC). Commonly sold as the acetate salt, salt counterions add ~60 Da per acetate, so stated mass is not pure peptide content unless a salt-corrected peptide content value is reported. Residual TFA from preparative HPLC mobile phases can be cytotoxic and is under-reported on research-grade COAs. No peer-reviewed stability study specific to ipamorelin has been identified; values above are vendor-derived.
Frequently asked questions
Is ipamorelin the same as CJC-1295, and why are they often sold together?
No, they are mechanistically distinct. Ipamorelin acts on the ghrelin receptor (GHS-R1a) to release GH. CJC-1295 is a GHRH analogue that acts on the GHRH receptor, a different receptor on the same pituitary cells. The rationale for combining them is that they act through complementary pathways and may produce synergistic GH release (the "dual-pulse" or "stack" hypothesis). This synergy has been demonstrated in animal models.
Does ipamorelin raise cortisol?
In animals (rats, pigs, dogs), ipamorelin does not raise ACTH or cortisol at doses up to 200× its GH-release ED₅₀ (Raun 1998). GHS-R1a pharmacology is largely conserved across species, so the animal finding is mechanistically plausible in a broader context, but the selectivity claim is based on animal data only and should be stated as such.
Is ipamorelin detectable in drug testing?
Yes. WADA has detection methods for GHS-class compounds including ipamorelin, and it is explicitly named in the 2026 Prohibited List under S2.2.4. Detection windows vary with analytical method (urine vs blood, LC-MS/MS sensitivity).
Does ipamorelin preserve "natural" GH pulsatility unlike exogenous GH injections?
This is a theoretically well-founded claim that is commonly supported by citing Ionescu & Frohman 2006 (JCEM, PMID 17018654), which is a CJC-1295 study, NOT an ipamorelin study. That misattribution is pervasive in ipamorelin marketing. The mechanistic principle (GHS release is somatostatin-feedback-governed) is sound and animal data on ipamorelin supports the pulsatile pattern, but ipamorelin-specific pulsatility evidence is limited to animal and in vitro models. Whether preserved-pulsatility would translate into better outcomes or different body composition is untested for this compound.
What should I look for on an ipamorelin COA?
Four things, separately reported: (1) salt form, acetate vs free base, with salt-corrected peptide content distinct from HPLC chromatographic purity, because each acetate counterion adds ~60 Da to stated mass; (2) chiral / stereochemistry confirmation (chiral HPLC or amino acid analysis) because the two critical D-amino acid residues (D-2-Nal, D-Phe) cannot be distinguished from L-isomers by standard reverse-phase HPLC; (3) residual TFA content, preparative HPLC leaves TFA as counterion unless converted via ion exchange; TFA is cytotoxic at high residuals; (4) endotoxin (LAL) testing per USP <85> because the product is injectable and bacterial endotoxin contamination causes fever and systemic toxicity at very low concentrations. A COA showing only "HPLC purity ≥98%" without these four items has not actually characterized what's in the vial.
Last researched: Apr 21, 2026
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