Overview
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue developed by Novo Nordisk in the mid-1990s. It belongs to a class of compounds that stimulate growth hormone release by acting on the growth hormone secretagogue receptor (GHSR, also known as the ghrelin receptor). Ipamorelin is distinguished from other GH secretagogues by its notable selectivity for growth hormone release without significantly affecting other pituitary hormones.
Contents
Overview Mechanism of Action Selective GHSR Agonism Synergy with GHRH Pathway Dose-Dependent Response Research Summary Selectivity Studies Postoperative Ileus Clinical Trials Bone Metabolism Growth Hormone Kinetics Dosing in Published Research Safety and Side Effects Current Research Status Frequently Asked Questions
Unlike earlier growth hormone releasing peptides such as GHRP-6 and GHRP-2, Ipamorelin does not cause significant increases in cortisol, prolactin, or adrenocorticotropic hormone (ACTH) at GH-stimulating doses. This selectivity profile has made it one of the most extensively studied GH secretagogues in both preclinical and clinical settings, with particular interest in its potential for growth hormone deficiency, age-related sarcopenia, and post-surgical recovery.
The peptide was advanced through Phase II clinical trials for postoperative ileus (delayed return of bowel function after surgery), conducted under the name NNC 26-0161. While the development program was ultimately discontinued, the clinical data generated provided valuable insights into the pharmacology and safety of selective GH secretagogues.
Mechanism of Action
Ipamorelin exerts its effects through highly selective agonism of the growth hormone secretagogue receptor type 1a (GHS-R1a), the same receptor targeted by the endogenous hormone ghrelin.
Selective GHSR Agonism
The GHS-R1a is a seven-transmembrane G-protein coupled receptor expressed in the hypothalamus and anterior pituitary. When activated by Ipamorelin, it triggers a Gq/11-phospholipase C-IP3 signaling cascade that raises intracellular calcium, stimulating GH release from somatotrophs. The key distinction of Ipamorelin is its narrow binding profile: it activates GHS-R1a without engaging other receptor subtypes or pathways that stimulate ACTH or prolactin secretion.
Synergy with GHRH Pathway
Ipamorelin acts synergistically with endogenous GHRH and its analogs (such as CJC-1295 and Mod GRF 1-29). While GHRH activates the cAMP-PKA pathway in somatotrophs, Ipamorelin activates the IP3-calcium pathway. These complementary mechanisms produce a greater GH response when combined than either agent alone, which is why the Ipamorelin/CJC-1295 combination has been widely studied in research contexts.
Dose-Dependent Response
Research has shown that Ipamorelin produces a dose-dependent, bell-shaped GH response curve. At optimal doses, it produces robust GH pulses with a rapid onset (peak at approximately 40 minutes post-injection) and relatively short duration, allowing for multiple daily administrations that mimic natural pulsatile GH secretion patterns.
Research Summary
Selectivity Studies
Raun et al. (1998), publishing in the European Journal of Endocrinology, conducted the landmark characterization of Ipamorelin’s selectivity. In swine models, Ipamorelin stimulated GH release in a dose-dependent manner comparable to GHRP-6, but unlike GHRP-6, it did not affect plasma ACTH or cortisol levels even at doses 200 times the effective GH-releasing dose. This study established Ipamorelin as the first truly selective GH secretagogue.
Postoperative Ileus Clinical Trials
Beck et al. (2008), in research published in the Journal of Surgical Research, reported results from a Phase II clinical trial of Ipamorelin for postoperative ileus following abdominal surgery. Intravenous Ipamorelin (0.03 mg/kg) significantly accelerated the time to first bowel movement and was well-tolerated with minimal adverse effects. A larger Phase IIb trial was conducted by Helsinn Healthcare but did not meet its primary endpoints, leading to discontinuation of development for this indication.
Bone Metabolism
Andersen et al. (2001), publishing in Bone, investigated the effects of Ipamorelin on bone formation in ovariectomized rats, a model for postmenopausal osteoporosis. Systemic administration of Ipamorelin for 12 weeks increased bone mineral content, bone formation rate, and periosteal mineral apposition rate, suggesting anabolic effects on bone that were mediated through sustained GH/IGF-1 elevation.
Growth Hormone Kinetics
Johansen et al. (1999), in Growth Hormone & IGF Research, performed detailed pharmacokinetic and pharmacodynamic analyses of Ipamorelin in healthy male volunteers. Subcutaneous injection of 1 mcg/kg produced peak GH levels of approximately 30 mcg/L at 40 minutes post-dose, with GH levels returning to baseline within 2-3 hours. No tachyphylaxis was observed with repeated dosing over 7 days.
Dosing in Published Research
About this section
The information below reports dosing only as it appears in published clinical or preclinical research and official regulatory documents. It is provided as published-literature reference material. It is not dosing guidance, not medical advice, and not a recommendation to use or self-administer this compound.
Ipamorelin is a synthetic growth-hormone secretagogue. It is not an approved medicine and has no labeled dose. Its most substantial human evaluation was a Phase 2 trial of postoperative ileus (ClinicalTrials.gov NCT00672074, sponsored by Helsinn), in which patients received intravenous ipamorelin at 0.03 mg per kilogram of body weight twice daily. The compound was not advanced to approval for that indication. These figures describe what was administered in that specific trial.
Research doses, not a protocol
The dose above comes from a single supervised clinical trial, not an established or recommended regimen. Ipamorelin remains an unapproved investigational compound, and material sold for research use is not a regulated drug product.
Safety and Side Effects
Ipamorelin has not been established as safe through completed clinical development. It is a growth hormone secretagogue, and its anticipated adverse effects follow from raising growth hormone and IGF-1: fluid retention, transient changes in insulin sensitivity and blood glucose, headache, and injection-site reactions. Ipamorelin is described as more selective than GHRP-6 and GHRP-2, with less stimulation of cortisol and prolactin, but selectivity reduces rather than eliminates off-target effects, and the sustained elevation of growth hormone and IGF-1 carries the same theoretical proliferative and metabolic concerns as other secretagogues. Long-term human safety data do not exist, and material sold as a research chemical is of uncertain identity and purity.
Current Research Status
Ipamorelin was investigated in early clinical studies, including for postoperative ileus, but was not advanced to regulatory approval; it is not approved by the FDA or any major regulatory agency. It is prohibited in sport by the World Anti-Doping Agency. It remains an investigational compound sold only through unregulated research-chemical channels.
Frequently Asked Questions
What is ipamorelin?
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue developed by Novo Nordisk in the mid-1990s. It was explored as a drug candidate, but development was discontinued, and it is now sold only as a research chemical.
How does ipamorelin work?
Ipamorelin selectively activates the growth hormone secretagogue receptor (GHS-R1a), the ghrelin receptor, in the pituitary and hypothalamus, triggering a short pulse of growth hormone release that mimics the body’s natural pulses.
Is ipamorelin FDA-approved?
No. Ipamorelin was investigated in early clinical studies, including for postoperative ileus, but was not advanced to regulatory approval. It is not approved by the FDA or any major regulatory agency and is prohibited in sport by WADA.
What does the research say about ipamorelin?
A landmark study by Raun and colleagues (1998) characterized ipamorelin’s selectivity, finding that in swine it stimulated growth hormone comparably to GHRP-6 but, unlike GHRP-6, did not meaningfully raise cortisol or prolactin. This relative selectivity is its most-noted feature.
What are the safety concerns with ipamorelin?
Ipamorelin has not been established as safe through completed clinical development. As a growth hormone secretagogue, its anticipated adverse effects follow from raising growth hormone and IGF-1, including fluid retention, transient changes in blood sugar, headache and injection-site reactions.
Research Handling & Storage
⚠ Important: The following information is compiled from published research literature and is provided strictly for educational and reference purposes. These compounds are sold for laboratory and research use only and are not intended for human consumption, self-administration, or any therapeutic application. Always comply with all applicable local, state, and federal regulations. Consult a qualified professional before handling any research compounds.
Reconstitution (General Guidelines)
Lyophilized peptides are typically reconstituted using bacteriostatic water (0.9% benzyl alcohol). Standard reconstitution protocol:
Remove the vial from storage and allow it to reach room temperature (20–25°C / 68–77°F) before opening. This typically takes 15–20 minutes. Clean the vial stopper with an alcohol prep pad and allow to air dry. Using a sterile syringe, slowly inject bacteriostatic water along the inside wall of the vial. Do not spray directly onto the lyophilized powder. Gently swirl the vial until the powder is fully dissolved. Do not shake vigorously as this may damage the peptide structure. The reconstituted solution should be clear and colorless. Discard if cloudy, discolored, or if particulate matter is visible. Label the vial with the reconstitution date, concentration, and your initials.
Common reconstitution volumes in research: 1ml or 2ml of bacteriostatic water per vial, depending on the desired concentration. For example, adding 2ml to a 5mg vial yields a concentration of 2.5mg/ml (2,500mcg/ml).
Storage
Lyophilized (unreconstituted): Store at -20°C (-4°F) for long-term storage (stable 24+ months), or 2–8°C (36–46°F) refrigerated for short-term storage up to 6 months. Keep desiccated and protected from light. Reconstituted: Store at 2–8°C (36–46°F) refrigerated. Use within 4–6 weeks of reconstitution. Do not freeze reconstituted solutions as this may cause degradation. Shipping: Lyophilized peptides are generally stable at ambient temperature during transit for several days. Reconstituted solutions should be shipped on ice packs.
Handling Precautions
Handle with appropriate personal protective equipment (PPE) including nitrile gloves, lab coat, and eye protection. Use aseptic/sterile technique when reconstituting and transferring solutions to prevent contamination. Avoid repeated freeze-thaw cycles which may denature the compound and reduce potency. Keep detailed laboratory records including reconstitution dates, lot numbers, concentrations, and storage conditions. Dispose of unused material and sharps in accordance with local regulations and institutional biosafety guidelines.
Stability & Shelf Life
Lyophilized (freeze-dried) peptides are highly stable when stored correctly. At -20°C (-4°F), most peptides retain >95% purity for 24 months or longer. Once reconstituted, the clock starts—proteins in solution are inherently less stable than in dry form. Factors that accelerate degradation include temperature fluctuations, exposure to light, repeated freeze-thaw cycles, bacterial contamination, and oxidation.
Purity & Quality Considerations
Research-grade compounds should be accompanied by a Certificate of Analysis (COA) confirming purity, typically verified by High-Performance Liquid Chromatography (HPLC) and Mass Spectrometry (MS). Look for purity levels of ≥98% for research applications. Third-party testing adds an additional layer of quality assurance. Always verify the source and documentation before using any research compound.
⚠ Reminder: This product and the information provided are intended exclusively for in-vitro research and laboratory use. Not for human or veterinary use. Not a drug, food, or cosmetic. The buyer assumes all responsibility for compliance with applicable laws and regulations.
Disclaimer: The information on peptides.fyi is provided for educational and research purposes only. This content is not intended as medical advice and should not be used to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional before making any decisions related to your health.