Ipamorelin (Growth Hormone Secretagogue)
Also Known AsNNC 26-0161 · Ipamorelin Acetate
Developed by Novo Nordisk as a highly selective growth hormone secretagogue peptide (GHSP). Identified through systematic modification of GHRP peptides to eliminate unwanted cortisol and prolactin release while retaining potent GH-releasing activity. First described in the late 1990s.
Aib-His-D-2-Nal-D-Phe-Lys-NH2How Ipamorelin Works
GHS-R1a (Ghrelin Receptor) Agonism
Selectively activates the growth hormone secretagogue receptor type 1a (GHS-R1a), a G-protein-coupled receptor expressed on pituitary somatotrophs. Unlike native ghrelin, ipamorelin shows minimal activity at GHS-R1a populations outside the pituitary, contributing to its selectivity profile.
Somatotroph Calcium Signaling
GHS-R1a activation triggers the Gq/11-PLC-IP3 cascade, releasing calcium from intracellular stores and opening voltage-gated calcium channels. The resulting calcium influx triggers GH vesicle exocytosis. This mechanism is distinct from and synergistic with the cAMP-PKA pathway activated by GHRH.
Selective GH Release
Ipamorelin's selectivity is defined by what it does NOT do: unlike GHRP-6 and GHRP-2, it does not significantly stimulate ACTH or cortisol release, and it produces minimal prolactin elevation. This selectivity is attributed to its pentapeptide structure lacking the lipophilic residues that engage off-target receptors.
Published Research
Growth Hormone Secretion
StrongDose-dependent, selective stimulation of GH release demonstrated in multiple species including human subjects. Peak GH levels occur approximately 40 minutes post-administration. GH release is amplified synergistically when co-administered with GHRH or GHRH analogs (e.g., CJC-1295 No DAC), confirming complementary receptor mechanisms.
Bone Metabolism
ModeratePreclinical and clinical studies demonstrate positive effects on bone mineral content and longitudinal bone growth. GH/IGF-1 axis activation stimulates osteoblast activity and periosteal bone formation. A Phase II clinical trial evaluated ipamorelin for post-operative ileus recovery, with bone effects as secondary endpoints.
Post-Operative Gastrointestinal Recovery
ModeratePhase II clinical trials evaluated ipamorelin for acceleration of GI recovery following abdominal surgery. Ghrelin receptor agonism in the enteric nervous system promotes gastric motility and intestinal transit, independent of the GH-releasing effects. Results showed trends toward reduced time to first bowel movement.
Body Composition in Aging
ModerateAge-related GH decline contributes to increased adiposity and decreased lean mass. Ipamorelin's ability to stimulate physiological GH pulses without cortisol or prolactin co-release makes it a candidate for studying GH axis restoration in aging populations without the confounding hormonal effects of less selective secretagogues.
Safety Profile
Ipamorelin has been evaluated in Phase I and Phase II clinical trials with a favorable safety profile. Transient side effects include mild headache, flushing, and injection site reactions. Critically, ipamorelin does not significantly elevate cortisol, ACTH, or prolactin at GH-stimulating doses — a key differentiator from GHRP-6 and GHRP-2. No dose-limiting toxicities reported in clinical studies.
Handling & Storage
Reconstitute with bacteriostatic water. Direct gentle stream along vial wall. Store lyophilized powder at -20°C. Reconstituted solution at 2-8°C, use within 21 days. Peptide is stable in solution at refrigerator temperature.
Peer-Reviewed Literature
- 1
Ipamorelin, the first selective growth hormone secretagogue
Raun K, Hansen BS, Johansen NL, et al.
- 2
Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers
Gobburu JV, Agersø H, Jusko WJ, Ynddal L.
- 3
Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats
Johansen PB, Nowak J, Skjaerbaek C, et al.
- 4
Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients
Beck DE, Sweeney WB, McCarter MD, et al.
Ipamorelin FAQ
What is Ipamorelin?
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue that selectively activates the GHS-R1a (ghrelin receptor) on pituitary somatotroph cells. It is notable for its selectivity — it stimulates GH release without significantly elevating cortisol, ACTH, or prolactin, distinguishing it from earlier GH secretagogues like GHRP-6.
How does Ipamorelin differ from GHRP-6?
Both are GHS-R1a agonists, but ipamorelin is highly selective for GH release only. GHRP-6 stimulates GH but also increases cortisol, prolactin, and appetite (via ghrelin-like hunger signaling). Ipamorelin's cleaner pharmacological profile is attributed to its distinct pentapeptide structure.
Why combine Ipamorelin with CJC-1295 (No DAC)?
Ipamorelin acts on the GHS-R1a (ghrelin receptor) while CJC-1295 (No DAC) acts on the GHRH receptor. These are separate signaling pathways (Gq/calcium vs. Gs/cAMP) on the same pituitary somatotroph cells. Simultaneous activation produces synergistic GH release exceeding what either compound achieves alone.
How should Ipamorelin be stored?
Store lyophilized powder at -20°C. Reconstitute with bacteriostatic water and refrigerate at 2-8°C. Use reconstituted solution within 21 days.
Has Ipamorelin been used in human clinical trials?
Yes. Ipamorelin was developed by Novo Nordisk and evaluated in Phase I/II clinical trials including studies on GH pharmacokinetics/pharmacodynamics and post-operative ileus. It was the first GH secretagogue to demonstrate selective GH release without cortisol or prolactin co-stimulation in human subjects.
Ipamorelin Products
All compounds 99%+ purity, verified by Janoshik Analytical. GMP-manufactured lyophilized powder.
Ipamorelin
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Disclaimer: This monograph is provided for educational and research purposes only. G26x Peptides products are sold exclusively as research chemicals. They are not intended for human consumption, therapeutic use, or as dietary supplements. All research should be conducted in compliance with applicable laws and institutional review board protocols. Information presented here is sourced from published peer-reviewed literature and does not constitute medical advice.