Growth Hormone Secretagogues Explained: Ipamorelin, CJC-1295, Sermorelin & Tesamorelin Compared
A side-by-side look at the four most-studied growth hormone secretagogues, how each one signals the pituitary, and where they overlap or differ mechanistically.
Growth hormone secretagogues are peptides that bind receptors on the pituitary gland and prompt it to release its own growth hormone (GH), rather than supplying synthetic GH directly. Ipamorelin, CJC-1295, sermorelin and tesamorelin are four widely studied secretagogues, and they engage the GH axis through one of two receptor pathways. Understanding those differences is the starting point for any GH-axis research design.
Two Receptor Families, One Target Cell
All four peptides act on pituitary somatotroph cells, but they arrive through one of two receptor systems:
- GHRH receptor agonists (sermorelin, CJC-1295, tesamorelin) mimic growth-hormone-releasing hormone. They bind the GHRH receptor, activate adenylyl cyclase through Gs-protein coupling, and raise intracellular cAMP, which primes GH synthesis and release.
- Ghrelin receptor agonists / GHRPs (ipamorelin) bind GHS-R1a, a Gq-coupled receptor that raises intracellular calcium and triggers exocytosis of stored GH granules.
Because these are separate second-messenger systems converging on the same cell, GHRH receptor and GHS-R1a signalling are studied as independent pathways.
Ipamorelin: Selective GHRP
Ipamorelin is a pentapeptide that binds GHS-R1a with high selectivity. Unlike older GHRPs such as GHRP-2 or GHRP-6, it does not meaningfully engage corticotropin-releasing pathways, and laboratory models report GH release without a corresponding rise in cortisol or prolactin. Its half-life is roughly two hours. See the ipamorelin product page for full mechanism detail.
CJC-1295 (no DAC): Short-Acting GHRH Analogue
Also known as Mod GRF 1-29, CJC-1295 without DAC is a stabilized fragment of GHRH(1-29) carrying four amino-acid substitutions that resist enzymatic breakdown. Its half-life is about 30 minutes, consistent with pulsatile rather than sustained receptor engagement. Full mechanism detail is on the CJC-1295 no DAC page.
Sermorelin: The Reference GHRH(1-29) Peptide
Sermorelin is the native GHRH(1-29) sequence itself. Its very short half-life (~7-12 minutes) keeps it fully subject to somatostatin feedback regulation, so it operates inside pulsatile signalling rather than overriding it. Details on the sermorelin product page.
Tesamorelin: Full-Length GHRH(1-44) Analogue
Tesamorelin is a stabilized analogue of full-length GHRH(1-44), marketed as Egrifta. Its half-life sits around 26-38 minutes. Published literature is listed on the tesamorelin product page.
Comparison Table
| Peptide | Receptor Target | Half-Life | Structural Note |
|---|---|---|---|
| Ipamorelin | GHS-R1a (ghrelin receptor) | ~2 hours | Pentapeptide, selective for GHS-R1a |
| CJC-1295 (no DAC) | GHRH receptor | ~30 minutes | GHRH(1-29) fragment with four substitutions |
| Sermorelin | GHRH receptor (native sequence) | ~7-12 minutes | Native GHRH(1-29) sequence |
| Tesamorelin | GHRH receptor (full-length analogue) | ~26-38 minutes | GHRH(1-44) analogue with N-terminal modification |
Two Second-Messenger Pathways
A GHRH receptor agonist and a ghrelin receptor agonist act on independent receptors on the same somatotroph cell: the first signals through cAMP, the second through intracellular calcium.
Other GH-axis compounds in the catalogue are listed in the related category. The catalogue lists ipamorelin and CJC-1295 individually and as a blend product.
Research Use Only
The peptides discussed in this article are sold strictly for laboratory and research use. Milo-Lab gives no use or dosing advice, and nothing here constitutes medical advice or a claim of benefit in humans. Consult the primary literature and your institution’s research guidelines before designing any study. For research purposes only. Not for human consumption.
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