Ipamorelin

What is Ipamorelin?

Ipamorelin is a synthetic pentapeptide growth hormone secretagogue with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂, molecular formula C₃₈H₄₉N₉O₅, molecular weight 711.85 g/mol, CAS 170851-70-4. Developed at Novo Nordisk and reported by Raun and colleagues in the European Journal of Endocrinology in 1998, it acts as an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), the receptor later identified as the ghrelin receptor. Its defining property is selectivity: in the original characterisation it stimulated growth hormone release with a potency and efficacy comparable to GHRP-6, but unlike GHRP-2 and GHRP-6 it produced no significant release of ACTH or cortisol even at doses more than 200-fold above its GH-releasing ED₅₀, which is why the 1998 paper titled it the first selective growth hormone secretagogue. Clinical development, including a programme in postoperative ileus, was discontinued, and it is not an approved medicine in any jurisdiction. Supplied as lyophilised powder for in-vitro research use only.

Ipamorelin vs GHRP-2 and GHRP-6

All three are short synthetic peptides acting at GHS-R1a, and the differences that matter experimentally are off-target hormone release and receptor pharmacology rather than the GH endpoint itself. GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂) was the first hexapeptide of the class and stimulates GH robustly, but also raises ACTH, cortisol and prolactin, and produces marked hunger signalling consistent with its activity at the ghrelin receptor. GHRP-2 is more potent on GH release than GHRP-6 in comparative studies but shares the same off-target profile, with measurable ACTH, cortisol and prolactin responses. Ipamorelin is the outlier: in the Raun 1998 characterisation it matched GHRP-6 for GH release in vitro and in vivo while showing no significant ACTH or cortisol response in swine even at very high multiples of the effective dose, and no meaningful prolactin release. For research designs where the question is GH-axis biology uncontaminated by simultaneous HPA-axis activation, that selectivity is the entire reason to choose ipamorelin over the older GHRPs; where the interplay of GH and ACTH release is itself the endpoint, GHRP-2 or GHRP-6 are the appropriate tools.

Ipamorelin Research Applications

Ipamorelin is used in endocrine research on GHS-R1a receptor pharmacology, where it serves as the standard selective agonist control against which newer secretagogues and the endogenous ligand ghrelin are compared. Reported applications include pituitary somatotroph signalling studies, pulsatile GH release kinetics in rodent and swine models, receptor binding and functional cAMP or calcium-mobilisation assays in GHS-R1a-transfected cell lines, and the dissection of GH-axis effects from HPA-axis effects that less selective GHRPs cannot cleanly separate. It also appears in bone metabolism work, where rat studies reported increased bone mineral content during ipamorelin administration, and in gastrointestinal motility research stemming from the discontinued postoperative ileus programme. It is frequently paired with GHRH-receptor agonists such as CJC-1295 or sermorelin to study the two-receptor convergence on somatotroph GH release.

Reconstitution Guide

Allow vials to reach room temperature, then sterilise the rubber stopper of both the peptide vial and the bacteriostatic water vial with an alcohol swab. Slowly draw your bacteriostatic water into a sterile insulin syringe, then inject it gently down the inner glass wall of the peptide vial, never directly onto the lyophilised powder. Once added, gently swirl the vial in a slow circular motion until fully dissolved. Never shake or vortex. Ipamorelin is a short, robust pentapeptide with non-natural residues that resist enzymatic attack, and it contains no methionine or cysteine, so handling is forgiving by peptide standards; aseptic technique remains the limiting factor. The solution should be clear and colourless. Label the vial with the reconstitution date and refrigerate immediately.

See our full peptide reconstitution guide and reconstitution calculator for step-by-step protocol.

Storage Instructions

Lyophilised vials should be stored at -20°C, protected from light and moisture, and remain stable for up to 24 months. Once reconstituted with bacteriostatic water, store the solution at 2-8°C and use within approximately 4 weeks, preparing single-use aliquots at -20°C for longer storage. The D-amino acids and aminoisobutyric acid residue that give ipamorelin its metabolic stability in biological matrices also make the stored solution comparatively resilient, but repeated freeze-thaw cycles and repeated stopper punctures remain the practical failure modes, so aliquot rather than re-enter one stock. Handle under sterile laboratory conditions throughout.

Frequently Asked Questions

Research References

• Ipamorelin, the first selective growth hormone secretagogue (Eur J Endocrinol, 1998)
• Selective GH-releasing pentapeptide ipamorelin in pigs (Endocrinology, 1998)

Related Research Compounds

• → CJC-1295 5mg
• → CJC-1295 + Ipamorelin 5+5mg
• → GHRP-2 5mg
• → Bacteriostatic Water 10ml