Ipamorelin
Also known as: Ipamorelin acetate, NNC 26-0161
3 notable studies · 6 references
TLDR
Ipamorelin is a selective ghrelin-receptor growth hormone secretagogue that reliably stimulates GH release in preclinical research, but human evidence is limited and common claims involving body composition, recovery, and anti-aging have not been established in controlled clinical trials.
Research Supports
- Studied for stimulating endogenous growth hormone release via the ghrelin receptor (GHS-R1a)
- Investigated for hormonal selectivity versus ACTH/cortisol release compared with other GHRPs
- Examined as a potential gastrointestinal prokinetic for postoperative ileus
- Investigated by FDA for compounded use in growth hormone deficiency and postoperative ileus
Observations Reported in Research
- Raun et al., 1998: GHRP-2/GHRP-6 raised ACTH and cortisol in swine; ipamorelin did not, even at high exposures
- 2009 rat postoperative-ileus model showed accelerated gastrointestinal transit after ipamorelin
- FDA's review found available clinical evidence did not support effectiveness for proposed uses
- Safety reports in the postoperative-ileus program included hypokalemia, hyperglycemia, and two deaths of unclear causation
These are brief summaries of what the referenced research examined or reported — not conclusions about safety or effectiveness, and not medical advice. See Notable Studies and Sources & References below for the full context and citations.
At a Glance
Classification: Synthetic pentapeptide; growth hormone secretagogue; ghrelin receptor / growth hormone secretagogue receptor agonist
Ipamorelin is a synthetic five-amino-acid growth hormone secretagogue developed to stimulate endogenous growth hormone release through the growth hormone secretagogue receptor, now generally known as the ghrelin receptor (GHS-R1a). Early experiments found that ipamorelin stimulated growth hormone release while producing substantially less ACTH and cortisol release than older growth hormone-releasing peptides such as GHRP-2 and GHRP-6. This selectivity became its defining research characteristic. Ipamorelin has subsequently been investigated in gastrointestinal motility and postoperative ileus because ghrelin-receptor signaling also affects the gastrointestinal tract. Despite its popularity in peptide and anti-aging communities, ipamorelin has not been FDA-approved, and controlled evidence supporting common claims involving muscle gain, fat loss, recovery, anti-aging, or improved body composition remains inadequate.
What Is Ipamorelin?
Ipamorelin is a synthetic pentapeptide, meaning it consists of five amino-acid residues. Its sequence is: Aib-His-D-2-Nal-D-Phe-Lys-NH₂ Researchers developed ipamorelin during efforts to produce growth hormone secretagogues with greater hormonal selectivity than earlier GHRPs. The original pharmacological work compared ipamorelin with GHRP-2 and GHRP-6. All three stimulated growth hormone release. However, GHRP-2 and GHRP-6 also increased ACTH and cortisol in animal experiments, whereas ipamorelin did not significantly increase those hormones even at exposures far above those needed to stimulate GH. This led researchers to describe ipamorelin as the first selective growth hormone secretagogue. That description has a specific meaning: selectivity for GH release in the experimental systems studied. It does not mean that ipamorelin has been established as safer or more effective than other GH secretagogues in humans.
What Are Researchers Studying?
Growth hormone secretion
The principal pharmacological action studied with ipamorelin is stimulation of endogenous growth hormone release. Early cell and animal experiments demonstrated potent GH release comparable with GHRP-6. Ipamorelin acts through the growth hormone secretagogue receptor rather than the GHRH receptor used by compounds such as tesamorelin and CJC-1295.
Hormonal selectivity
One of the original goals in developing ipamorelin was separating growth-hormone stimulation from some of the additional endocrine effects produced by earlier GHRPs. In swine experiments, GHRP-2 and GHRP-6 increased ACTH and cortisol concentrations. Ipamorelin did not produce significant ACTH or cortisol increases compared with GHRH, even at exposures more than 200 times greater than the amount required for half-maximal GH release. This finding established ipamorelin's reputation as a relatively selective GH secretagogue. Whether this translates into a superior long-term human safety profile has not been established.
Ghrelin-receptor signaling
Ipamorelin belongs to the synthetic growth hormone secretagogue family that activates the same receptor system subsequently identified as the receptor for the endogenous hormone ghrelin. Ghrelin-receptor signaling affects more than growth hormone secretion. It participates in appetite regulation, gastrointestinal function, energy metabolism, and neuroendocrine signaling. This broader biology helps explain why ipamorelin has also been investigated for effects on gastrointestinal motility.
Gastrointestinal motility
Ghrelin and synthetic ghrelin-receptor agonists can influence gastrointestinal movement. Researchers therefore investigated ipamorelin as a potential treatment for postoperative ileus, a temporary impairment of intestinal motility that can occur following surgery. Animal experiments demonstrated accelerated gastrointestinal transit in models of postoperative ileus. This led to human clinical development, although the human program did not establish ipamorelin as an approved treatment.
Growth hormone deficiency
Because ipamorelin stimulates endogenous growth hormone release, it has been proposed as a potential treatment for growth hormone deficiency. FDA reviewed ipamorelin free base and ipamorelin acetate in connection with proposed compounding for growth hormone deficiency. The agency concluded that available evidence did not adequately support effectiveness and identified unresolved safety and product-characterization concerns.
Body composition and aging
Ipamorelin is frequently promoted outside the scientific literature for muscle growth, fat loss, recovery, sleep, or “anti-aging.” These claims are largely extrapolated from its ability to stimulate the GH/IGF-1 axis. Demonstrating that a compound increases growth hormone does not establish that it improves these clinical outcomes. Adequately controlled human trials supporting these common uses have not been established.
How Does It Work?
Ipamorelin primarily activates the growth hormone secretagogue receptor type 1a (GHS-R1a), commonly called the ghrelin receptor. This distinguishes it mechanistically from GHRH analogues. CJC-1295 / Tesamorelin → GHRH receptor Ipamorelin / GHRP-2 / GHRP-6 → Ghrelin/GHS receptor Activation of GHS-R1a within the hypothalamic-pituitary system stimulates release of growth hormone from pituitary somatotroph cells. Growth hormone can subsequently increase production of IGF-1 and influence metabolic and growth-related signaling. Early pharmacological experiments demonstrated that antagonists of the GHRP/GHS pathway inhibited ipamorelin-induced GH release, while a GHRH antagonist did not, supporting a mechanism distinct from direct GHRH-receptor agonism. The ghrelin receptor is also expressed outside the pituitary and participates in gastrointestinal and metabolic signaling, helping explain ipamorelin's effects on intestinal motility.
What Does the Research Show?
Human research
Human evidence for ipamorelin is limited. This is important because the compound's online popularity can make its clinical evidence appear considerably stronger than it actually is. Ipamorelin entered clinical development, including investigation as a gastrointestinal prokinetic for postoperative ileus. However, the program did not establish an approved indication. FDA's detailed review identified human clinical information from the postoperative-ileus development program but concluded that available clinical evidence did not support effectiveness for the proposed uses evaluated by the agency. Safety findings in the postoperative-ileus program included reports of: • Hypokalemia • Hyperglycemia • Insomnia • Nausea • Vomiting • Abdominal distension Two deaths occurred among ipamorelin-treated subjects. Importantly, FDA stated that it was unclear whether those deaths were caused by ipamorelin. They therefore should not be described as confirmed ipamorelin-related deaths. FDA also reported that it had not identified safety data for the subcutaneous route proposed in the compounding nomination it evaluated. There is not an established controlled human evidence base demonstrating that ipamorelin improves muscle growth, recovery, fat loss, aging, or athletic performance.
Animal research
The foundational evidence for ipamorelin comes primarily from animal experiments. In the original 1998 characterization study, ipamorelin stimulated growth hormone release in rats and conscious swine. Its potency and efficacy were broadly comparable to GHRP-6 in those experimental systems. Most notably, ipamorelin demonstrated substantially greater endocrine selectivity than GHRP-2 and GHRP-6 with respect to ACTH and cortisol release. Later animal research investigated gastrointestinal effects. In a rat model of postoperative ileus, ipamorelin accelerated gastrointestinal transit and improved measures of postoperative intestinal function. These experiments established biological activity but cannot establish clinical efficacy or long-term safety in humans.
In-vitro research
Ipamorelin has been studied in cultured pituitary cells and receptor-based experimental systems. The original characterization demonstrated dose-dependent GH release from primary rat pituitary cells, with potency and efficacy similar to GHRP-6. Subsequent pharmacological work helped establish the relationship between synthetic GH secretagogues and the GHS-R1a/ghrelin receptor system. These studies are useful for understanding receptor pharmacology but cannot establish clinical benefits.
Notable Studies
Ipamorelin, the First Selective Growth Hormone Secretagogue
animalResearchers characterized the pharmacology and endocrine selectivity of ipamorelin. Ipamorelin stimulated GH release from cultured rat pituitary cells and produced potent GH release in rats and swine. GHRP-2 and GHRP-6 increased ACTH and cortisol in swine, while ipamorelin did not produce significant increases compared with GHRH even at exposures substantially greater than those required for GH release. The researchers therefore characterized ipamorelin as the first GHRP-receptor agonist demonstrating GH selectivity similar to GHRH.
Limitations: The key experiments were conducted in cultured rat cells, rats, and swine. Hormonal selectivity in animal models does not establish long-term safety, efficacy, or endocrine selectivity in humans.
View publication →Efficacy of Ipamorelin, a Novel Ghrelin Mimetic, in a Rodent Model of Postoperative Ileus
animalResearchers investigated whether ipamorelin could accelerate gastrointestinal transit following experimentally induced postoperative ileus in rats. Ipamorelin was administered after surgery, and researchers evaluated colonic transit, fecal output, food intake, and body weight. The findings supported prokinetic activity and provided rationale for clinical investigation of ipamorelin in postoperative ileus.
Limitations: This was an animal model. Improved gastrointestinal transit in rats cannot establish efficacy or safety for postoperative ileus in humans.
View publication →FDA Evaluation of Ipamorelin and Ipamorelin Acetate for the 503A Bulks List
animalFDA evaluated ipamorelin free base and ipamorelin acetate for proposed compounded uses including growth hormone deficiency and postoperative ileus. The review examined chemical characterization, historical use, preclinical research, available clinical studies, effectiveness, and safety. FDA concluded that the available information weighed against adding the substances to the 503A Bulks List, citing inadequate evidence of effectiveness, limited physicochemical characterization, and unresolved safety concerns.
Limitations: This was a regulatory evidence assessment rather than a new clinical experiment. The decision concerned suitability for pharmacy compounding and should not be interpreted as evidence that ipamorelin lacks biological activity.
View publication →What We Still Don't Know
Major unanswered questions include: • Whether ipamorelin effectively treats growth hormone deficiency • Whether it produces clinically meaningful improvements in body composition • Whether it improves muscle mass or strength in humans • Whether it meaningfully affects fat loss • Whether it improves recovery or physical performance • Long-term effects on glucose metabolism • Long-term consequences of increased GH/IGF-1 signaling • Long-term cardiovascular safety • Human endocrine selectivity during repeated exposure • Immunogenicity • Effects of peptide aggregation and impurities • Safety of commonly proposed injectable routes • Whether ipamorelin offers meaningful clinical advantages over other GH secretagogues FDA specifically identified insufficient information concerning immunogenicity and aggregation and noted the absence of safety data for the proposed subcutaneous route evaluated in the compounding review.
Related Compounds
Recent publications
Latest titles from PubMed, not reviewed by Aminodex. Not an endorsement. See all on PubMed ↗
Take the Ipamorelin research with you.
Get the Aminodex Ipamorelin Brief—a concise summary of the research, notable studies, evidence types, limitations, and references.
One-time email. We do not add you to any mailing list.
Sources & References
- Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the First Selective Growth Hormone Secretagogue. European Journal of Endocrinology. 1998.
- Venkova K, Mann W, Nelson R, Greenwood-Van Meerveld B. Efficacy of Ipamorelin, a Novel Ghrelin Mimetic, in a Rodent Model of Postoperative Ileus. Journal of Pharmacology and Experimental Therapeutics. 2009.
- Hansen BS et al. Pharmacological Characterisation of a New Oral GH Secretagogue, NN703. 1999.
- Arvat E, Broglio F, Aimaretti G, et al. Ghrelin and Synthetic GH Secretagogues. Best Practice & Research Clinical Endocrinology & Metabolism. 2002;16(3):505–517.
- U.S. Food and Drug Administration. Pharmacy Compounding Advisory Committee meeting, October 29, 2024 (ipamorelin-related bulk drug substances).
- U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks.
Supplier Listings
Disclosure: The owner of Aminodex operates the supplier(s) marked below. These listings are promotion for businesses we own, not independent recommendations. Read our disclosures.