What Is Ipamorelin?

What Is Ipamorelin?. Complete research guide to Ipamorelin: GHS-R1a mechanism, selectivity data, published studies, and how it compares to other GHRPs. Key Takeaways Ipamorelin is a synthetic pentapeptide growth hormone secretagogue (GHS) that selectively activates the GHS-R1a (ghrelin) receptor to stimulate pulsatile growth hormone release. Originally developed by Novo Nordisk in the mid-1990s, it was characterized in pivotal research by Raun et al. (1998). Its key research differentiator is selectivity — preclinical data shows GH release without significant elevation of cortisol, prolactin, or ACTH, unlike GHRP-2 and GHRP-6. Ipamorelin is not FDA approved for any indication and remains available only as a research compound. Researchers frequently combine Ipamorelin with CJC-1295 (a GHRH analog) to study dual-pathway GH amplification. What Is Ipamorelin? Ipamorelin is a synthetic pentapeptide classified as a growth hormone releasing peptide (GHRP) . It was developed by Novo Nordisk in the mid-1990s as part of a research program investigating selective growth hormone secretagogues. The compound was first characterized in detail in a landmark 1998 publication by Raun et al. in the European Journal of Endocrinology , which established its pharmacological profile as a selective GHS-R1a agonist. Unlike earlier GHRPs such as GHRP-2 and GHRP-6, Ipamorelin was specifically designed to minimize off-target endocrine effects. Researchers have observed that it stimulates growth hormone release from anterior pituitary somatotrophs without significantly affecting cortisol, prolactin, or adrenocorticotropic hormone (ACTH) levels — a selectivity profile that has made it one of the most widely studied GHRPs in preclinical research. Chemical Identity Ipamorelin belongs to the pentapeptide class of growth hormone secretagogues. Its structure incorporates several non-natural amino acid modifications that enhance receptor binding affinity and metabolic stability compared to endogenous ghrelin. Molecular Properties Property Value Systematic Name Aib-His-D-2-Nal-D-Phe-Lys-NH₂ Molecular Formula C₃₈H₄₉N₉O₅ Molecular Weight 711.85 Da CAS Number 170851-70-4 Structure Class Synthetic pentapeptide Receptor Target GHS-R1a (growth hormone secretagogue receptor type 1a) Development Novo Nordisk (NNC 26-0161) The sequence includes α-aminoisobutyric acid (Aib) at position 1, D-2-naphthylalanine (D-2-Nal) at position 3, and D-phenylalanine (D-Phe) at position 4. These non-natural residues contribute to the compound's binding selectivity and resistance to enzymatic degradation. Mechanism of Action: GHS-R1a Agonist Ipamorelin exerts its effects through selective agonism of the growth hormone secretagogue receptor type 1a (GHS-R1a) , also known as the ghrelin receptor. This G protein-coupled receptor is primarily expressed on somatotroph cells in the anterior pituitary gland. When Ipamorelin binds to GHS-R1a, it triggers an intracellular signaling cascade: Receptor activation — Ipamorelin binds the GHS-R1a receptor on pituitary somatotrophs Phospholipase C pathway — Gq/11 protein coupling activates PLC, generating IP3 and DAG Calcium mobilization — IP3-mediated calcium release from intracellular stores triggers GH vesicle exocytosis Pulsatile GH release — Growth hormone is released in a physiological pulsatile pattern, preserving hypothalamic feedback A critical distinction in Ipamorelin's mechanism is that it preserves the hypothalamic-pituitary feedback axis . Unlike exogenous GH administration, which can suppress endogenous GH production, Ipamorelin works through the body's existing regulatory architecture. Researchers have observed that the GH pulses stimulated by Ipamorelin remain subject to somatostatin-mediated negative feedback, meaning the system self-regulates rather than producing supraphysiological, sustained GH elevation. GHRP vs GHRH: Understanding the Difference Growth hormone release is governed by two opposing hypothalamic signals: GHRH (growth hormone releasing hormone) , which stimulates release, and somatostatin , which inhibits it. Research peptides in this space fall into two distinct mechanistic categories: GHRH analogs (e.g., CJC-1295, Sermorelin, Tesamorelin ) — bind the GHRH receptor on pituitary somatotrophs to directly stimulate GH synthesis and release GHRPs / Ghrelin mimetics (e.g., Ipamorelin, GHRP-2, GHRP-6, Hexarelin) — bind the GHS-R1a receptor to amplify GH release through a separate, complementary pathway Ipamorelin falls firmly in the GHRP/ghrelin mimetic category. This distinction matters for researchers because the two pathways are synergistic — which is why CJC-1295 + Ipamorelin combinations are so widely studied. GH Secretagogue Comparison Compound Class Receptor FDA Status Ipamorelin GHRP (ghrelin mimetic) GHS-R1a Not approved CJC-1295 GHRH analog GHRH-R Not approved Sermorelin GHRH analog GHRH-R Previously approved (Geref®, discontinued) Tesamorelin GHRH analog GHRH-R FDA approved (Egrifta®) GHRP-2 GHRP (ghrelin mimetic) GHS-R1a Not approved GHRP-6 GHRP (ghrelin mimetic) GHS-R1a Not approved Selectivity Profile: The Key Research Differentiator What makes Ipamorelin stand out among GHRPs is its endocrine selectivity . In the pivotal Raun et al. (1998) study, researchers compared the hormonal effects of Ipamorelin against GHRP-6 and GHRP-2 in swine models. The findings established Ipamorelin's defining characteristic: Growth hormone — Ipamorelin produced dose-dependent GH release comparable to GHRP-6 Cortisol — No significant cortisol elevation was observed with Ipamorelin, while GHRP-2 and GHRP-6 produced measurable cortisol increases Prolactin — No significant prolactin elevation at GH-effective concentrations ACTH — No significant ACTH stimulation, contrasting with the adrenocorticotropic effects of other GHRPs GHRP Selectivity Comparison (Preclinical Data) Compound GH Release Cortisol Effect Prolactin Effect ACTH Effect Ipamorelin ✓ Dose-dependent Minimal / none Minimal / none Minimal / none GHRP-2 ✓ Dose-dependent ↑ Moderate increase ↑ Moderate increase ↑ Moderate increase GHRP-6 ✓ Dose-dependent ↑ Moderate increase ↑ Moderate increase ↑ Moderate increase Hexarelin ✓ Strong ↑↑ Significant increase ↑↑ Significant increase ↑↑ Significant increase Data adapted from Raun et al. (1998), European Journal of Endocrinology. All observations from preclinical (swine) models. This selectivity profile is the primary reason Ipamorelin has become one of the most referenced GHRPs in contemporary peptide research. Published Research Ipamorelin has been characterized across multiple published studies spanning from the late 1990s through the 2000s. The key publications that established its pharmacological profile include: Study Year Journal Key Finding Raun et al. 1998 European Journal of Endocrinology Established Ipamorelin's selective GH release without cortisol/ACTH elevation in swine models Johansen et al. 1999 Growth Hormone & IGF Research Characterized pharmacokinetic profile and dose-response relationships Hansen et al. 2002 European Journal of Endocrinology Confirmed selectivity in human volunteers; no cortisol/prolactin changes at GH-effective concentrations Jimenez-Reina et al. 2002 Pituitary Investigated GHS-R1a receptor binding kinetics and compared with other secretagogues The Hansen et al. (2002) study is particularly notable because it extended the selectivity observations from animal models to human subjects, confirming that Ipamorelin produced robust GH elevation without significant changes in cortisol, ACTH, prolactin, or FSH/LH levels. Combination Research: CJC-1295 + Ipamorelin One of the most widely studied peptide combinations in GH research is CJC-1295 + Ipamorelin . The rationale is dual-pathway activation: CJC-1295 (GHRH analog) → activates the GHRH receptor to stimulate GH synthesis and baseline release Ipamorelin (ghrelin mimetic) → activates GHS-R1a to amplify GH pulse amplitude By engaging both regulatory pathways simultaneously, researchers have observed synergistic GH elevation greater than either compound alone. The combination also preserves the physiological pulsatile pattern of GH release, as both pathways remain subject to somatostatin feedback. Regulatory Status Ipamorelin is not FDA approved for any indication. It has never completed Phase III clinical trials and remains classified as a research compound. Unlike Tesamorelin (Egrifta®), which received FDA approval in 2010 for HIV-associated lipodystrophy, Ipamorelin has not progressed through the regulatory pipeline. The compound is available for purchase as a research chemical through laboratory supply vendors. Researchers comparing supply options can browse our Ipamorelin product page . It is not approved for human therapeutic use, and any research use should comply with applicable institutional and regulatory guidelines. For a comprehensive deep-dive into Ipamorelin's regulatory history, clinical trial status, and comparison with approved alternatives, see our dedicated guide: Ipamorelin FDA Approval Status 2026 . For a broader view of which peptides have achieved regulatory approval, see our pillar article: FDA Approved Peptides List 2026 . Laboratory Handling Ipamorelin is supplied as a lyophilized (freeze-dried) powder and requires proper storage and reconstitution for research use. Storage Lyophilized (unreconstituted): Store at -20°C for long-term stability. Short-term storage at 2-8°C (refrigerated) is acceptable for peptides that will be used within weeks. Reconstituted: Store at 2-8°C and use within 4-6 weeks. Avoid repeated freeze-thaw cycles, which can degrade peptide integrity. Light sensitivity: Protect from direct light. Store in amber vials or opaque containers when possible. Reconstitution Reconstitute with bacteriostatic water (BAC water) or sterile water for injection. The standard approach: Allow the vial to reach room temperature before reconstitution Direct the solvent gently down the interior wall of the vial — do not inject directly onto the lyophilized cake Swirl gently; do not shake vigorously Allow the solution to sit until fully dissolved (may take several minutes) For precise concentration calculations based on your reconstitution volume, use our free Peptide Reconstitution Calculator . Need help determining how much bacteriostatic water to add? Try our BAC Water Calculator . Frequently Asked Questions What is Ipamorelin used for in research? Ipamorelin is used in preclinical and laboratory research to study growth hormone secretion pathways. Its selective GHS-R1a agonism — producing GH release without cortisol or prolactin elevation — makes it a valuable tool for investigating the growth hormone axis in isolation from other endocrine effects. How does Ipamorelin differ from GHRP-2 and GHRP-6? The primary difference is selectivity. While all three compounds stimulate growth hormone release via the GHS-R1a receptor, preclinical data from Raun et al. (1998) showed that Ipamorelin does not significantly elevate cortisol, prolactin, or ACTH at GH-effective concentrations. GHRP-2 and GHRP-6 produce measurable increases in these hormones. Is Ipamorelin FDA approved? No. Ipamorelin has never received FDA approval for any indication. It remains available only as a research compound. Why do researchers combine CJC-1295 with Ipamorelin? CJC-1295 (a GHRH analog) and Ipamorelin (a ghrelin mimetic) activate two different receptors that regulate growth hormone release. By stimulating both the GHRH-R and GHS-R1a pathways simultaneously, researchers have observed synergistic GH elevation while maintaining physiological pulsatile release patterns. How should Ipamorelin be stored? Lyophilized Ipamorelin should be stored at -20°C for long-term stability or 2-8°C for short-term use. Once reconstituted, store at 2-8°C and use within 4-6 weeks. Avoid repeated freeze-thaw cycles and protect from direct light. Disclaimer: This article is for informational and educational purposes only. Ipamorelin is a research compound and is not approved by the FDA for any therapeutic use. PeptideStack does not provide medical advice, and all products referenced are intended for laboratory and research use only. Not for human consumption. Always consult applicable institutional guidelines and regulations before conducting research with any compound. PeptideStack page context: visitors can use the header navigation to reach the product catalog, blog, calculators, supplier pages, discount-code pages, contact page, legal policies, shipping policy, refund policy, privacy policy, terms, and research disclaimer. The site is organized around research peptide education, supplier transparency, product comparison, vendor review content, discount-code tracking, and calculator tools for reconstitution or unit conversion research planning. PeptideStack separates research-use-only peptide information from FDA-approved medication and licensed telehealth pathways. Research peptide pages are informational and are not medical advice, prescription guidance, dosing instructions, treatment recommendations, or instructions for human consumption. Many pages include affiliate disclosures because PeptideStack may earn a commission when visitors click external supplier or telehealth links. That commission does not change the price paid by visitors and does not mean PeptideStack manufactures, sells, distributes, compounds, or ships peptides or medications. Supplier and product pages should be evaluated for third-party testing, batch-specific certificates of analysis, named laboratory verification, transparent pricing, realistic delivery expectations, payment security, refund policies, support quality, and consistent research-use-only labeling. Blog pages connect related guides, comparison articles, FDA approval status explainers, safety context, legality resources, product pages, vendor reviews, and calculator tools so visitors can keep researching without relying on a single supplier claim. Calculator pages are educational tools for laboratory planning and should be cross-checked against professional protocols, institutional requirements, and applicable laws. Legal and disclaimer pages explain the boundaries of PeptideStack content and the responsibility of visitors who evaluate third-party vendors. The rendered interface may add interactive details such as mobile navigation labels, product tabs, share buttons, related article cards, disclosure boxes, call-to-action buttons, vendor selectors, copy-code controls, email-code forms, footer navigation, and status labels. The static HTML fallback includes this context so the same page purpose is understandable before the JavaScript application finishes loading. Visitors should treat PeptideStack as a research and comparison starting point. Final supplier evaluation should include direct review of the external vendor website, current product availability, checkout terms, applicable laws, institutional requirements, and any third-party laboratory documentation available for the exact product or batch being considered. Footer resources repeat important sitewide context: PeptideStack is independent, affiliate-supported, research-focused, and not a pharmacy or manufacturer. Pages may include links to the iOS app, calculators, blog hubs, product hubs, supplier comparisons, support contact, and policy documents. This repeated context is intentionally available in the raw HTML for crawlers that inspect a page before executing the React bundle. Raw HTML also includes page summaries for mobile crawlers using JavaScript rendering, desktop crawlers comparing source to rendered output, accessibility tools, and no-script visitors. The fallback is replaced by the React app in normal browsers but keeps the source document aligned with the visible page topic. This fallback keeps source HTML and rendered HTML closer for crawl diagnostics and SEO audits across crawled pages, routes, reports, and recrawls.