Ipamorelin

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) that acts as a selective agonist of the ghrelin receptor (GHSR-1a), also called the growth hormone secretagogue receptor. It was developed by Novo Nordisk and has been studied extensively in preclinical and early clinical settings.

Ipamorelin belongs to the growth hormone-releasing peptide (GHRP) family, which includes GHRP-2, GHRP-6, and Hexarelin. Among this class, Ipamorelin is particularly notable for its selectivity: it strongly stimulates GH release while having minimal effects on cortisol (stress hormone) or prolactin (as compared to GHRP-2 and GHRP-6, which can significantly elevate both). This selectivity makes Ipamorelin a cleaner GH-stimulating tool for research purposes.

Unlike CJC-1295 (which acts through GHRH receptors), Ipamorelin acts through the ghrelin/GHS receptor — a distinct and complementary GH-releasing pathway. This complementarity is why the CJC-1295 + Ipamorelin combination is so widely used: the two peptides stimulate GH release through different pathways that act synergistically.

Ipamorelin is not FDA-approved for human use. It has been studied in clinical trials (primarily for postoperative ileus) but did not receive regulatory approval for that indication.

Ipamorelin's mechanism centers on ghrelin receptor activation:

• GHSR-1a agonism: Ipamorelin binds with high affinity and selectivity to the ghrelin receptor (growth hormone secretagogue receptor 1a, GHSR-1a) on pituitary somatotroph cells. This activates phospholipase C and increases intracellular calcium, triggering GH granule exocytosis.
• Selectivity for GH over cortisol/prolactin: Ipamorelin's selectivity for GHSR-1a without activating related receptors (or with much lower activation) compared to older GHRPs is the key pharmacological advantage. GHRP-6 and GHRP-2 co-activate receptors that drive cortisol and prolactin release; Ipamorelin largely avoids this.
• Synergy with GHRH: The GHRH pathway (activated by CJC-1295) and the ghrelin/GHS pathway (activated by Ipamorelin) converge in the pituitary to produce additive-to-synergistic GH secretion. Natural GH pulsatility involves both pathways, and combining their pharmacological analogs recapitulates a more physiological GH release pattern.
• GH pulse amplification: Rather than causing continuous GH secretion, Ipamorelin (especially combined with CJC-1295) produces large, distinct GH pulses, which is consistent with the natural secretion pattern.
• Downstream IGF-1: Released GH acts on the liver to stimulate IGF-1 production, mediating muscle anabolic and fat catabolic effects.

Ipamorelin's benefits follow from GH/IGF-1 elevation, with advantages from its selectivity profile:

• Lean muscle growth: Elevated IGF-1 from increased GH output drives muscle protein synthesis, satellite cell activation, and hypertrophy. The absence of cortisol elevation (unlike some GHRPs) means less catabolic interference with muscle building.
• Fat loss: GH's direct lipolytic effects promote fat mobilization; the favorable GH:cortisol ratio of Ipamorelin may support body recomposition more effectively than less selective GHRPs.
• Improved recovery: GH and IGF-1 support tissue repair and recovery from both exercise and injury.
• Sleep quality: Increased GH secretion during sleep (particularly deep NREM sleep) may improve sleep quality and the restorative effects of sleep.
• Anti-aging profile: GH and IGF-1 decline substantially with age. Ipamorelin-stimulated GH production may partially address age-related declines in muscle mass, bone density, and skin quality.
• Lower side effect burden: Compared to older GHRPs and direct GH administration, Ipamorelin's selectivity profile generally produces fewer and milder side effects, making it better tolerated for extended research use.

Ipamorelin's side effect profile is generally considered one of the most favorable among GH-stimulating peptides:

• Injection site reactions: Minor discomfort, redness, or swelling at the subcutaneous injection site
• Headache: Reported in some users, typically mild and transient
• Water retention: Mild fluid retention from elevated GH, typically less pronounced than with direct GH
• Appetite stimulation: As a ghrelin receptor agonist, Ipamorelin may increase appetite in some individuals (though less than GHRP-6, which has marked appetite-stimulating effects)
• Facial flushing: Reported shortly after injection
• Carpal tunnel symptoms: Possible with higher doses due to GH-induced fluid shifts

Absent or minimized compared to other GHRPs:

• Cortisol elevation (Ipamorelin does not significantly increase cortisol)
• Prolactin elevation
• Strong hunger stimulation (unlike GHRP-6)

IGF-1 elevation concerns and theoretical cancer risk considerations apply to Ipamorelin as they do to all GH-stimulating peptides.

Disclaimer: Ipamorelin is not FDA-approved for human use. The following is for educational purposes only.

Common research protocols:

• Standard dose: 200–300 mcg per injection, administered subcutaneously
• Frequency: 1–3 times per day; before-bed dosing is common to enhance nocturnal GH pulsatility
• With CJC-1295 (without DAC): 100–300 mcg Ipamorelin + 100 mcg CJC-1295 without DAC per injection, 1–2x daily
• Timing: Best administered in a fasted state or 2+ hours after meals to avoid insulin-blunted GH response
• Cycle length: Typically 8–16 week cycles described in the research community

Ipamorelin is reconstituted from lyophilized powder with bacteriostatic water. Subcutaneous injection is the standard route; intramuscular is less common.

Ipamorelin has been studied in both preclinical and clinical settings:

• Preclinical GH studies: Extensive animal research confirms selective GH release with minimal cortisol or prolactin elevation at effective doses, validating the selectivity advantage over older GHRPs.
• Postoperative ileus trial: Novo Nordisk studied Ipamorelin (as part of a prodrug program) for postoperative gastrointestinal dysmotility in Phase II trials, reflecting GHS receptor activity in the GI tract. The compound did not advance through clinical development for this indication.
• Body composition studies: Animal research demonstrates improved body composition (increased lean mass, decreased fat mass) with Ipamorelin treatment, consistent with GH/IGF-1 effects.
• Bone density: Some animal studies show improved bone mineral density and collagen synthesis relevant to osteoporosis prevention.

Ipamorelin has less published clinical trial data than some other peptides despite its widespread use in the research community. Its favorable selectivity profile is well-characterized in animals but comprehensive human pharmacology data is limited.