What is Ipamorelin?
Ipamorelin is a pentapeptide (five amino acid) growth hormone secretagogue (GHS) developed by Novo Nordisk in the late 1990s. It mimics the action of ghrelin — the “hunger hormone” — by binding to the growth hormone secretagogue receptor (GHS-R, also called the ghrelin receptor) in the pituitary gland.
Its key advantage over earlier GH secretagogues (like GHRP-2 and GHRP-6) is its high selectivity: it stimulates GH release without significantly increasing cortisol, prolactin, or ACTH (adrenocorticotropic hormone), which are common unwanted effects with less selective compounds.
How Ipamorelin Works
- Binds to GHS-R1a receptors in the pituitary gland and hypothalamus
- Triggers a pulse of growth hormone release from the anterior pituitary
- Released GH stimulates IGF-1 production in the liver
- GH and IGF-1 promote muscle protein synthesis, lipolysis, bone formation, and cellular repair
Selective vs Non-Selective Secretagogues
| Compound | GH Release | Cortisol Elevation | Prolactin Elevation |
|---|---|---|---|
| Ipamorelin | Strong | Minimal | Minimal |
| GHRP-2 | Strong | Moderate | Moderate |
| GHRP-6 | Strong | Moderate | High |
This selectivity makes ipamorelin the preferred choice in research settings where minimizing hormonal side effects is important.
Common Research Applications
Ipamorelin is frequently used in combination with CJC-1295 (a GHRH analogue) because:
- They work on different receptors (GHS-R vs GHRH-R)
- They produce synergistic GH release
- The combination mimics the natural dual-signal required for optimal pituitary GH secretion
Side Effects
- Generally mild due to high selectivity
- Mild water retention
- Headache (uncommon)
- Injection site reactions
- At high doses: increased hunger (ghrelin-like effect)
Medical Disclaimer: Ipamorelin is not FDA-approved and is available for research purposes only. Growth hormone pathway manipulation carries risks including potential insulin resistance and should only be considered under qualified medical supervision.
Related Reading
- Ipamorelin and CJC-1295: The GH Secretagogue Stack Explained — Evidence review of the ipamorelin + CJC-1295 combination including pulsing protocols
- Sermorelin: Growth Hormone Therapy Guide — Compare ipamorelin with sermorelin for GH stimulation
- Peptide Combination Therapy: Evidence and Principles — How to combine GH secretagogues safely with other peptides
- Peptide Therapy for Aging and Sarcopenia — GH secretagogue use in older adults: benefits, risks, and monitoring
- Peptide Therapy Lab Monitoring Guide — IGF-1 targets and safety monitoring for GH axis peptides
Safety Profile Summary
Strong preclinical safety profile. Highly selective — does not significantly elevate cortisol, prolactin, or ACTH unlike older secretagogues. Human clinical data is limited.
References & Further Reading
- 1. Raun K, et al. Ipamorelin, the First Selective Growth Hormone Secretagogue. Eur J Endocrinol. 1998;139(5):552-61. [PubMed ↗]
- 2. Johansen PB, et al. Ipamorelin, a New Growth-Hormone-Releasing Peptide, Induces Longitudinal Bone Growth in Rats. Growth Horm IGF Res. 1999;9(2):106-13. [PubMed ↗]
- 3. Svensson J, et al. Two-Month Treatment of Obese Subjects with the Oral Growth Hormone (GH) Secretagogue MK-677 Increases GH Secretion, Fat-Free Mass, and Energy Expenditure. J Clin Endocrinol Metab. 1998;83(2):362-9. [PubMed ↗]
- 4. ClinicalTrials.gov — Studies on Ipamorelin. [ClinicalTrials.gov ↗]