Ipamorelin
Also known as: Ipamorelin Acetate, NNC 26-0161
Ipamorelin is a selective growth hormone secretagogue and ghrelin receptor agonist. It stimulates the release of growth hormone from the pituitary gland without significantly affecting cortisol or prolactin levels.
Key Findings at a Glance
- •Ipamorelin is called the first truly selective growth hormone secretagogue because it stimulates GH release without measurably raising cortisol, prolactin, or ACTH at therapeutic doses.
- •Unlike most GHRPs, Ipamorelin preserves the natural pulsatile rhythm of growth hormone release rather than forcing a continuous elevation, maintaining normal feedback regulation.
- •Ipamorelin has only a handful of human studies, primarily pharmacokinetic trials and a discontinued Phase II for postoperative ileus, making its widespread popularity largely based on animal data.
- •In glucocorticoid-treated rats mimicking osteoporosis, Ipamorelin counteracted steroid-induced bone loss by enhancing bone formation without changing bone mineral density markers.
Ipamorelin Overview & Molecular Profile
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue that acts as a selective agonist at the ghrelin receptor (GHSR-1a). First described by Raun et al. in 1998, it is distinguished from other GHRPs by releasing GH without meaningfully elevating cortisol, prolactin, or ACTH at therapeutic doses—a selectivity profile unique among its class. Human data is limited to two PK/PD studies and a discontinued Phase II trial; the majority of evidence derives from rodent models.
Mechanism of Action: Hormonal Signaling & Receptor Binding
Ipamorelin acts as an agonist at the ghrelin receptor (GHSR-1a) in the pituitary gland, stimulating the release of growth hormone through activation of specific signaling pathways (PMID: 9849822). It mimics the action of the natural hormone ghrelin but with higher selectivity. The peptide stimulates GH release in a dose-dependent manner while maintaining the natural pulsatile pattern of GH secretion. Importantly, it does not significantly stimulate ACTH, cortisol, or prolactin release at physiological doses (PMID: 9849822).
Research-Observed Effects
Growth Hormone Release
Research demonstrates significant, dose-dependent increases in growth hormone levels following Ipamorelin administration (PMID: 9849822), with peak GH concentrations occurring approximately 30-40 minutes post-injection (PMID: 10496658). Studies consistently show that Ipamorelin maintains the natural pulsatile pattern of GH secretion rather than causing unnatural sustained elevation, which is considered beneficial for maintaining normal feedback regulation (PMID: 9849822). While Ipamorelin's human data is limited (primarily PK/PD studies and a discontinued Phase II for postoperative ileus), the dose-dependent acute stimulation aligns with 3-10 fold increases in peak GH, with effects lasting approximately 2-3 hours per administration (PMID: 10496658). The peptide has been studied for optimization of natural GH production patterns (PMID: 9849822), though it has not been extensively studied for age-related hormone decline or adult growth hormone deficiency in clinical trials.
Selective GH Stimulation
One of Ipamorelin's most significant research advantages is its remarkable selectivity for growth hormone release without substantial effects on other pituitary hormones or stress hormones. Clinical studies demonstrate minimal impact on cortisol levels (unlike GHRP-6 and GHRP-2), negligible prolactin elevation, and no significant effects on FSH, LH, TSH, or ACTH at therapeutic dosages. This selectivity profile makes Ipamorelin invaluable for research requiring isolated study of GH pathway effects without confounding hormonal variables. The peptide's clean hormonal profile has made it the preferred GHRP for many endocrinology research applications studying GH deficiency, aging, and metabolic regulation.
Body Composition Effects
Research in animal models and preliminary human studies indicates Ipamorelin may influence body composition through GH-mediated pathways including enhanced lipolysis (fat breakdown), increased lean body mass, and improved fat-free mass to fat mass ratios. Studies have documented potential effects on visceral adipose tissue (belly fat), subcutaneous fat distribution, and skeletal muscle protein synthesis. The peptide has been investigated for applications in obesity research, sarcopenia (age-related muscle loss) studies, and metabolic syndrome investigations. Long-term administration studies in animals suggest sustained improvements in body composition metrics without significant adverse effects.
Bone Density Research
Studies suggest Ipamorelin may positively influence bone metabolism through mechanisms involving growth hormone and IGF-1 elevation (PMID: 9849822, PMID: 10373343). While GH and IGF-1 positively influence bone metabolism, the direct effect of Ipamorelin on bones is less studied. Research in animal models has documented increased longitudinal bone growth in young subjects (PMID: 10373343) and increased bone mineral content (BMC) due to increased volume of bone, though bone mineral density itself remained unchanged (PMID: 10828840). Note: No significant changes in bone turnover markers (osteocalcin and bone-specific alkaline phosphatase) were observed in studies (PMID: 10373343, PMID: 10828840). The peptide was studied in an osteoporosis-mimicking model (glucocorticoid-induced bone loss in adult rats), where it enhanced bone formation (PMID: 11735244). Studies show Ipamorelin causes pulsatile GH release (not sustained elevation), indicating it may preserve normal feedback regulation while potentially supporting bone remodeling processes.
Sleep and Recovery Research
The relationship between growth hormone secretion and sleep quality is well-established in endocrinology research, as natural GH release peaks during slow-wave (deep) sleep. Since Ipamorelin stimulates pulsatile GH release that mimics natural patterns (PMID: 9849822), researchers have hypothesized potential benefits for sleep architecture. However, direct studies specifically evaluating Ipamorelin's effects on sleep quality metrics are limited. Any observed sleep-related effects would theoretically be mediated through GH pathway activation rather than direct CNS effects. Further research is needed to establish whether Ipamorelin administration influences sleep architecture, recovery processes, or subjective sleep quality in controlled settings.
Research Dosing Information
| Route | Dose | Frequency | Notes |
|---|---|---|---|
| Subcutaneous | 1–3 mcg/kg | 1–3× daily | Mimics pulsatile GH secretion; most studied route |
| Intravenous | 1–3 mcg/kg | Single dose | Used in PK/PD studies (PMID: 10496658) |
| Intraperitoneal | 1–3 mcg/kg | Daily | Rodent bone and metabolic studies |
Note: Dosing information is provided for research reference only and is based on published studies using research subjects. This is not a recommendation for any use.
Research Studies & References
Ipamorelin, the first selective growth hormone secretagogue
Raun K, Hansen BS, Johansen NL, et al. (1998). European Journal of Endocrinology
This foundational study established Ipamorelin as a selective growth hormone secretagogue, demonstrating its unique ability to stimulate GH release without significantly affecting cortisol, prolactin, or ACTH levels. The research showed dose-dependent GH release while maintaining natural pulsatile secretion patterns. This selectivity profile distinguished Ipamorelin from earlier GHRPs like GHRP-6 and GHRP-2, establishing it as a valuable tool for isolated GH research.
Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers
Gobburu JV, Agersø H, Jusko WJ, Ynddal L (1999). Pharmaceutical Research
This PK/PD study in human volunteers documented Ipamorelin's pharmacokinetic profile, showing peak GH concentrations approximately 30-40 minutes post-injection with effects lasting 2-3 hours. The research established dose-response relationships and confirmed the peptide's favorable pharmacological characteristics for GH research applications.
Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats
Johansen PB, Nowak J, Skjaerbaek C, et al. (1999). Growth Hormone & IGF Research
This study demonstrated Ipamorelin's effects on longitudinal bone growth in rat models. Researchers documented increased tibial bone length through GH-mediated mechanisms. Notably, no significant changes in bone turnover markers (osteocalcin, bone-specific alkaline phosphatase) were observed, indicating effects primarily through bone volume rather than remodeling markers.
The GH secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats
Andersen NB, Malmlöf K, Johansen PB, et al. (2001). Growth Hormone & IGF Research
This study investigated Ipamorelin in a glucocorticoid-induced bone loss model (mimicking osteoporosis conditions). Results showed Ipamorelin enhanced bone formation in adult rats treated with dexamethasone, suggesting potential applications in studying GH-based interventions for steroid-induced bone loss.
Comparative Research
Explore in-depth research analyses and comparative studies featuring Ipamorelin.
Comparative Clinical Analysis
CJC-1295 vs Ipamorelin: GHRH Analog vs GHRP Comparison for Growth Hormone Research
CJC-1295 and Ipamorelin represent two complementary mechanisms for stimulating growth hormone release, which is why they are frequently combined in research settings. CJC-1295, a GHRH (growth hormone ...
Hexarelin vs Ipamorelin: GHRP Potency vs Selectivity Comparison for Research
Hexarelin and Ipamorelin represent opposite ends of the GHRP spectrum: maximum potency versus maximum selectivity. Hexarelin is the most potent GHRP for acute GH release but carries significant off-ta...
Ipamorelin vs Sermorelin: GHRP vs GHRH Comparison for GH Secretion | Peptpedia
Ipamorelin and Sermorelin represent two distinct mechanistic approaches to growth hormone stimulation. Ipamorelin is a GHRP (ghrelin receptor agonist) that amplifies GH pulse amplitude; Sermorelin is ...
BPC-157 vs Ipamorelin: Healing Peptide vs GH Secretagogue Comparison | Peptpedia
BPC-157 and Ipamorelin target entirely different physiological systems: BPC-157 is a tissue repair peptide derived from gastric juice that promotes healing through angiogenesis and fibroblast activati...
Frequently Asked Questions
What makes Ipamorelin selective compared to other GHRPs?
Unlike GHRP-6 and GHRP-2, Ipamorelin stimulates GH release without meaningfully elevating cortisol, prolactin, or ACTH at physiological doses (PMID: 9849822). This is because Ipamorelin has high selectivity for the GHSR-1a receptor on pituitary somatotrophs and does not significantly activate the adrenocortical axis or stimulate prolactin-releasing pathways. It also lacks the potent ghrelin-mimetic appetite-stimulating effects seen with GHRP-6, making it cleaner for isolated GH research.
What human clinical data exists for Ipamorelin?
Ipamorelin's human data is limited to two published pharmacokinetic/pharmacodynamic studies: a 1999 PK/PD study (PMID: 10496658) that documented dose-response relationships and peak GH at 30-40 minutes post-injection in human volunteers, and a Phase II clinical trial for postoperative ileus (NCT00272649) that was discontinued. No published human efficacy trials for GH deficiency, body composition, or anti-aging applications exist. The extensive preclinical literature should not be conflated with established human clinical efficacy.
How does Ipamorelin preserve the natural pulsatility of GH secretion?
Ipamorelin stimulates GH release in discrete pulses that clear from circulation relatively quickly (plasma half-life approximately 2 hours), allowing the pituitary to return to baseline between doses. This mirrors the natural pattern of GH secretion, which occurs in 4-6 pulses per day—predominantly during deep sleep. Continuous GH elevation (as with exogenous GH administration) suppresses this natural pulsatility and can downregulate GH receptors. Ipamorelin's pulsatile profile may better preserve normal GH axis feedback compared to sustained-release compounds.
How does Ipamorelin compare to CJC-1295?
They work through complementary but different mechanisms. Ipamorelin activates the ghrelin receptor (GHSR-1a), while CJC-1295 activates the GHRH receptor on the same pituitary somatotroph cells. Because these are separate receptor systems, the combination produces synergistic GH release greater than either alone. CJC-1295 (with DAC) provides sustained background GH elevation lasting days, while Ipamorelin creates acute GH pulses. The combination protocol exploits both pathways simultaneously to maximize GH output.
What bone research has been done with Ipamorelin?
Ipamorelin has been studied in two bone-related rodent models. A 1999 study (PMID: 10373343) showed increased longitudinal bone growth (tibial length) with no significant change in bone turnover markers (osteocalcin, BSAP)—suggesting growth through increased bone volume rather than remodeling. A 2001 study (PMID: 11735244) found Ipamorelin partly counteracted glucocorticoid-induced bone formation loss in adult rats. These findings suggest bone-supportive effects mediated through GH/IGF-1 but do not establish clinical efficacy for osteoporosis prevention.
Can Ipamorelin be combined with other peptides?
In research settings, Ipamorelin is frequently studied in combination with GHRH analogs like CJC-1295 or Sermorelin. The synergistic effect arises because the two receptor pathways (GHSR-1a for Ipamorelin, GHRHR for the GHRH analog) amplify each other's pituitary stimulation. This combination has been shown to produce 2-5× greater GH release than either compound alone. Combinations with other peptides have not been formally studied in published clinical research.
What is the half-life of Ipamorelin?
Human pharmacokinetic data from the 1999 PK/PD study (PMID: 10496658) documented a plasma half-life of approximately 2 hours in humans. Peak GH concentrations occurred 30-40 minutes post-subcutaneous injection, with GH effects persisting 2-3 hours. The relatively short half-life supports multi-daily dosing protocols designed to create GH pulses that mimic the natural circadian pattern of growth hormone secretion.
What side effects have been observed with Ipamorelin in research?
In published human PK/PD studies, Ipamorelin demonstrated a favorable tolerability profile. Unlike GHRP-6, it does not significantly stimulate appetite (minimal ghrelin-mimetic effects at the hypothalamic level). Unlike GHRP-2, it does not significantly elevate cortisol or ACTH. Common mild observations in studies include transient facial flushing and headache. No serious adverse events specific to Ipamorelin were documented in the limited published human data. The long-term safety profile in humans is not established due to the absence of extended clinical trials.
CJC-1295
C152H252N44O42
CJC-1295 is a synthetic analog of growth hormone releasing hormone (GHRH) with a Drug Affinity Complex that extends its half-life significantly compared to native GHRH.
GHRP-6
C46H56N12O6
GHRP-6 is a synthetic hexapeptide that stimulates growth hormone release through the ghrelin receptor. It was one of the first growth hormone releasing peptides developed.