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 prompt the pituitary gland to release its own growth hormone (GH), rather than supplying synthetic GH directly. Ipamorelin, CJC-1295, sermorelin and tesamorelin are the four most-studied secretagogues, and each engages the GH axis through a distinct receptor pathway. Understanding those differences is the starting point for any GH-axis research design.
Searches for terms like “HGH Thailand” or “human growth hormone Thailand” usually reflect interest in raising GH output for research into recovery, body composition, or aging biology. Foreign-market HGH brands are outside what this article covers. The compounds below are the legal, well-characterized research route to the same axis: they stimulate the body’s own pituitary rather than introducing exogenous hormone.
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 agonists and GHRP agonists are frequently studied together rather than as substitutes for one another.
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, so research models show GH release without a corresponding spike 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. It clears in about 30 minutes, reinforcing the body’s natural GH pulses rather than holding GH continuously elevated. Full mechanism and stacking notes are on the CJC-1295 no DAC page.
Sermorelin: The Reference GHRH(1-29) Peptide
Sermorelin is the native GHRH(1-29) sequence itself, with the deepest pharmacological track record of the four (it was previously marketed as Geref for pediatric GH-deficiency testing). Its very short half-life (~7-12 minutes) keeps it fully subject to somatostatin feedback, so it operates inside the body’s natural pulsatile rhythm 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) and the only GHRH-axis peptide with FDA approval (as Egrifta), based on Phase 3 trials showing visceral adipose tissue reduction (Falutz et al., NEJM 2010) and a defined effect in HIV-associated lipodystrophy (J Acquir Immune Defic Syndr 2010). A separate randomized trial also reported cognitive changes in older adults with mild cognitive impairment (J Clin Endocrinol Metab 2019). Its half-life sits around 26-38 minutes. See the tesamorelin product page.
Comparison Table
| Peptide | Receptor Target | Half-Life | Research Focus |
|---|---|---|---|
| Ipamorelin | GHS-R1a (ghrelin receptor) | ~2 hours | Selective, pulsatile GH release without cortisol/prolactin rise |
| CJC-1295 (no DAC) | GHRH receptor | ~30 minutes | Short-acting GHRH amplification, pulsatility preserved |
| Sermorelin | GHRH receptor (native sequence) | ~7-12 minutes | Reference GHRH pharmacology, longest evidence base |
| Tesamorelin | GHRH receptor (full-length analogue) | ~26-38 minutes | Only FDA-validated GHRH peptide; visceral fat and IGF-1 research |
Why GHRH and GHRP Peptides Are Often Studied Together
Because a GHRH agonist and a GHRP agonist act on independent receptors on the same somatotroph cell, combining one from each category is a standard design in GH-axis research. The Ipamorelin + CJC-1295 blend exists specifically for that paired protocol, pairing the cAMP-driven GHRH signal with the calcium-driven GHRP signal for a larger, still-pulsatile GH pulse than either compound alone.
For the full set of GH-axis peptides Milo-Lab carries, see the Performance & Growth category.
Research Use Only
The peptides discussed in this article are sold strictly for laboratory and research use. Nothing here constitutes medical advice, a treatment protocol, or a claim of therapeutic benefit in humans. Consult the primary literature and your institution’s research protocols before designing any study.
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