GH Secretagogues Explained: GHRH Analogues and GHRPs

GH secretagogues are peptides studied for their ability to stimulate the body’s own growth hormone (GH) release, rather than introducing synthetic GH directly. CJC-1295, Ipamorelin, Tesamorelin, Sermorelin, Hexarelin and GHRP-6 are six of the more researched compounds in this category, and they get grouped together in search more often than the underlying pharmacology justifies. They don’t all work the same way.

CJC-1295, Tesamorelin and Sermorelin target the same receptor pathway, the GHRH receptor. Ipamorelin, Hexarelin and GHRP-6 target a completely different one, the ghrelin receptor, which is why this second group is commonly called GHRPs (Growth Hormone Releasing Peptides) rather than GHRH analogues. Understanding that split is the fastest way to make sense of why these compounds keep appearing together, and why certain pairings, like CJC-1295 and Ipamorelin, are researched together far more than others.

What are GH secretagogues?

A GH secretagogue is any compound that prompts the pituitary gland to release its own growth hormone, rather than supplying GH from an external source. This distinction matters for research design: because the pituitary retains control of the release, secretagogues tend to preserve the body’s natural pulsatile GH pattern instead of producing a single sustained spike.

Growth hormone is normally released in bursts throughout the day, driven by alternating signals from GHRH and somatostatin, the hormone that suppresses GH release. A secretagogue works within that existing feedback loop rather than overriding it, which is the main pharmacological distinction researchers draw between secretagogues and exogenous GH administration.

Within the GH secretagogue category, compounds fall into two distinct receptor families.

GHRH receptor agonists are structurally modified versions of growth hormone-releasing hormone (GHRH). They bind directly to the GHRH receptor on pituitary somatotroph cells, stimulating GH synthesis and release. CJC-1295 and Tesamorelin and Sermorelin belong to this family.

Ghrelin receptor agonists work through an entirely separate receptor, the growth hormone secretagogue receptor (GHS-R1a), also known as the ghrelin receptor. Ipamorelin, Hexarelin and GHRP-6 all belong to this family. This group is also widely referred to as GHRPs, Growth Hormone Releasing Peptides, a term that predates the more precise “ghrelin receptor agonist” classification and is still the more commonly searched name.

Because these two pathways are independent, research has explored combining a GHRH receptor agonist with a ghrelin receptor agonist to produce a more pronounced GH pulse than either compound achieves alone, which is the basis for CJC-1295 and Ipamorelin’s frequent pairing.

CJC-1295: what it is and how it works

CJC-1295 is a synthetic analogue of GHRH, developed to extend the very short duration of action that limits native GHRH’s usefulness in research settings. It binds the GHRH receptor on the anterior pituitary and stimulates growth hormone synthesis and release along the same pathway the body uses naturally.

CJC-1295 exists in two research formulations: with and without DAC (Drug Affinity Complex). The DAC variant binds to serum albumin in circulation, which substantially extends its half-life compared to the no-DAC form, allowing less frequent dosing in a research protocol.

A 2006 randomised, placebo-controlled study in the Journal of Clinical Endocrinology & Metabolism examined CJC-1295 with DAC in healthy adults across ascending single and multiple-dose trials. It reported dose-dependent increases in growth hormone of two to ten times baseline, alongside a sustained rise in IGF-1 lasting nine to eleven days after a single dose, with no serious adverse reactions recorded during the study period.

Research into CJC-1295 has focused primarily on the effects of sustained GH axis stimulation on body composition, fat metabolism and markers of tissue anabolism, rather than on a single specific outcome measure.

Ipamorelin: what it is and how it works

Ipamorelin is a synthetic pentapeptide developed in the late 1990s as a growth hormone secretagogue with improved receptor selectivity compared to earlier GHRPs in its class, such as GHRP-6, covered later in this article. Structurally and mechanistically, it has nothing in common with CJC-1295.

Rather than binding the GHRH receptor, Ipamorelin activates GHS-R1a, the same receptor that the body’s own hormone ghrelin uses to stimulate GH release. This is the mechanism that makes Ipamorelin a ghrelin receptor agonist rather than a GHRH analogue.

The original 1998 study in the European Journal of Endocrinology that characterised Ipamorelin found it produced potent, dose-dependent GH release without meaningfully raising ACTH, cortisol or prolactin, even at doses far above the threshold needed for GH release. This selectivity, GH stimulation without the broader hormonal cascade seen in earlier ghrelin mimetics, is the property most associated with Ipamorelin in the research literature.

Why CJC-1295 and Ipamorelin are often paired

CJC-1295 and Ipamorelin act on two separate receptors that both feed into GH release. Research into combining GHRH receptor stimulation with GHS-R1a activation has found the pairing produces a more robust GH pulse than either compound alone, which is why the two are so frequently studied together rather than in isolation.

This complementary mechanism is the entire basis for pairing them. Tesamorelin and Sermorelin don’t fit the same role, because they activate the same receptor pathway as CJC-1295 rather than a different one, which is why neither is typically combined with CJC-1295 in the same way. Specific research protocols and dosing schedules for combined use sit outside the scope of this overview and are a matter for a qualified professional.

Tesamorelin: what it is and how it works

Tesamorelin is a synthetic growth hormone-releasing factor (GHRF) analogue. Mechanistically, it belongs to the same GHRH receptor family as CJC-1295, activating GHRH receptors on the pituitary to stimulate growth hormone synthesis and release, which then acts on tissues throughout the body, including the liver, where it drives IGF-1 production.

What separates Tesamorelin from CJC-1295 is its regulatory and research history. Tesamorelin is the only compound of the three that holds FDA approval, specifically for the reduction of excess abdominal fat in HIV-infected adults with lipodystrophy, marketed as EGRIFTA. That approval comes with clearly stated limitations of use: it is not indicated for general weight loss management, and its long-term cardiovascular safety has not been established.

The clinical evidence behind that approval is more extensive than the CJC-1295 or Ipamorelin research base. Pooled data from two multicentre, double-blind, placebo-controlled Phase 3 trials found Tesamorelin reduced visceral adipose tissue by approximately 15 to 20% relative to placebo over 26 to 52 weeks of daily use, with the reduction generally reversing within several months of stopping treatment.

This clinical grounding is why Tesamorelin functions as a mechanistic cousin of CJC-1295 rather than an interchangeable alternative. The two share a receptor pathway, but Tesamorelin’s research base is narrower in scope and considerably deeper in clinical documentation.

Beyond visceral fat reduction, a separate 2014 trial published in JAMA found tesamorelin also produced modest reductions in liver fat over six months, closely correlated with the change in visceral fat, in a smaller cohort of 48 treated patients. The pivotal Phase 3 programme underpinning the FDA approval separately tracked secondary endpoints including triglycerides and lean body mass. The FDA label is explicit that these effects are weight-neutral rather than a general weight-loss outcome, and that the visceral fat reduction observed in trials was not sustained once daily dosing stopped.

Sermorelin: the third GHRH analogue

Sermorelin is the third GHRH receptor agonist in this category, and in some ways the original. It’s the shortest synthetic peptide that retains full GHRH activity, comprising just the first 29 amino acids of the native 44-amino-acid hormone.

Sermorelin held FDA approval in the 1990s, marketed as Geref, for diagnosing growth hormone deficiency in children. It was voluntarily withdrawn from the US market by 2008 as longer-acting GHRH analogues such as CJC-1295 became available, a commercial decision rather than a safety finding.

Because Sermorelin sits so close to CJC-1295 mechanistically, a full side-by-side comparison between the two deserves its own dedicated article rather than a few paragraphs here.

Hexarelin: what it is and how it works

Hexarelin is a synthetic hexapeptide GHRP, meaning it activates the same ghrelin receptor (GHS-R1a) as Ipamorelin. What makes it a genuinely distinct compound in this category is a second, separate mechanism: Hexarelin also binds CD36, a receptor found in cardiac tissue that has nothing to do with growth hormone release.

That dual-receptor profile is why Hexarelin has attracted research interest beyond the GH axis. In ischemia-reperfusion injury models, Hexarelin has been shown to protect heart tissue through CD36-mediated signalling, independent of its effect on growth hormone. This cardioprotective research is a genuinely separate line of investigation from its use as a GH secretagogue, and one of the more interesting aspects of the compound.

Because Hexarelin activates the ghrelin receptor rather than the GHRH receptor, it sits in the same family as Ipamorelin and GHRP-6, not CJC-1295 or Tesamorelin, despite occasionally being described loosely as hitting “both pathways.” The cardiac research specifically involves CD36, a distinct receptor entirely, rather than any interaction with the GHRH receptor.

Browse Hexarelin research compound.

GHRP-6: what it is and how it works

GHRP-6 was one of the earliest synthetic GHRPs developed, and it remains one of the most extensively studied. Like Ipamorelin and Hexarelin, it activates the ghrelin receptor (GHS-R1a) to stimulate GH release, and research from the 1990s established that it produces a strong synergistic effect on GH release when combined with a GHRH analogue.

The key difference between GHRP-6 and Ipamorelin is selectivity. GHRP-6 predates the more receptor-selective compounds that followed it, and it’s well documented in the research literature as increasing appetite and producing modest prolactin and cortisol effects alongside GH release, effects that Ipamorelin’s improved selectivity was specifically designed to avoid. This is the main reason the two are rarely treated as interchangeable in research despite sharing a receptor.

River Peptides supplies GHRP-6 as both an injectable acetate and a nasal spray, a non-injectable delivery route not available for most other compounds in this category.

Are these GH secretagogues safe? What the research says

Safety research across these compounds varies substantially in depth, largely reflecting how much clinical study each has undergone.

CJC-1295, Ipamorelin and Sermorelin. All three have been studied primarily in short-duration trials though Sermorelin has the longest track record given its historic FDA approval for paediatric growth hormone deficiency diagnosis in healthy adults. The available data describes them as generally well tolerated, with injection site reactions as the most commonly reported effect. None have undergone the scale of long-term clinical study that Tesamorelin has, so questions like is CJC-1295 safe or is Ipamorelin safe are best answered with reference to the specific study population and duration involved, rather than as a blanket statement.

Hexarelin and GHRP-6. Both are well characterised in the research literature given decades of study, but that research base skews toward animal and short-duration human pharmacology studies rather than the kind of large clinical trials Tesamorelin has undergone. GHRP-6’s appetite-stimulating and prolactin/cortisol effects are well documented; Hexarelin’s dual-receptor profile means its research spans both GH-axis studies and a separate cardiovascular research literature.

Tesamorelin. Because Tesamorelin has a wider clinical trial base, its side effect profile is better characterised. Reported effects include:

• Injection site reactions
• Joint and muscle pain
• Fluid retention
• Gastrointestinal discomfort

On the question of does Tesamorelin cause cancer, growth hormone-releasing compounds are generally not recommended for people with cancer or an increased cancer risk, because of their role in stimulating cellular replication, and this is reflected in Tesamorelin’s prescribing information rather than being a claim specific to this article.

None of these compounds are approved for general human use in the UK, and River Peptides sells them strictly for research purposes, not for human consumption. Nothing in this article should be read as medical advice or a recommendation for personal use.

How are these compounds typically researched? Reconstitution basics

Peptides supplied as lyophilised powder require reconstitution with bacteriostatic water before use in a research setting. Published research protocols and product labelling describe general principles rather than a single universal figure, and the correct approach depends on the specific compound, concentration and research design in question.

As a general reference point, standard research vials are typically reconstituted using a volume that fits within a 3mL container, with the exact amount depending on the target concentration for the study.

This table reflects what has been reported in published research and product labelling, not a recommended protocol. Anyone reconstituting a peptide for research purposes should follow the specific product’s documentation and standard laboratory practice.

GHRH analogues at a glance

GHRPs at a glance

Explore GH-axis research at River Peptides

Understanding how GHRH analogues and GHRPs differ is the first step before deciding which, if any, is relevant to your research. Every batch River Peptides supplies is independently verified by accredited third-party laboratories, including Janoshik and Analiza Biatek, and the business holds ISO 9001 and ISO 14001 accreditation. You can review the full testing methodology and results on our quality testing page.

Browse our CJC-1295 and Ipamorelin blend, Ipamorelin, Tesamorelin, Sermorelin, Hexarelin and GHRP-6 (also available as a nasal spray) research compounds, or see the full growth secretagogue range.

If you’re specifically weighing up Tesamorelin against another compound, our detailed Pinealon vs Tesamorelin comparison covers the mechanisms, research and safety profile of both in depth.

Frequently Asked Questions

What is the difference between a GHRH analogue and a GHRP?

GHRH analogues (CJC-1295, Tesamorelin, Sermorelin) activate the GHRH receptor, the same pathway the body’s own GHRH uses. GHRPs (Ipamorelin, Hexarelin, GHRP-6) activate a separate receptor, the ghrelin receptor, and are sometimes just called Growth Hormone Releasing Peptides. Both stimulate GH release, but through different mechanisms, which is why they’re often combined in research.

Is CJC-1295 a steroid?

No. CJC-1295 is a peptide, a short chain of amino acids that mimics GHRH. It does not share the chemical structure or mechanism of anabolic steroids, which act on androgen receptors rather than the GH axis.

Does Ipamorelin increase testosterone?

Ipamorelin’s research focus is GH release through the ghrelin receptor. The studies that established its selectivity specifically found it does not meaningfully affect ACTH, cortisol or prolactin, and it is not studied as a testosterone-modulating compound.

Is GHRP-6 the same as Ipamorelin?

No. Both are GHRPs acting on the ghrelin receptor, but GHRP-6 is older and less selective, with well-documented appetite and prolactin effects that Ipamorelin’s design specifically avoids.

Is Hexarelin the same as Ipamorelin?

No. Hexarelin shares the ghrelin receptor mechanism with Ipamorelin but also binds a second, unrelated receptor called CD36, which is the basis for a separate line of cardiovascular research distinct from its GH-releasing effect.

Is Sermorelin the same as CJC-1295?

Both are GHRH receptor agonists, but Sermorelin is a shorter, unmodified fragment of native GHRH with a short half-life, while CJC-1295 is a structurally modified analogue designed to extend that half-life significantly, particularly in its DAC form.

Does Tesamorelin increase testosterone?

Tesamorelin’s clinical trial data centres on visceral fat reduction and a rise in GH/IGF-1 rather than testosterone. Its prescribing information does not list testosterone modulation as an indicated or studied effect.

Why is Tesamorelin so expensive compared to CJC-1295 or Ipamorelin?

Tesamorelin’s cost generally reflects its more extensive clinical development and FDA-approved manufacturing standard, in contrast to CJC-1295 and Ipamorelin, which remain research compounds without an equivalent approval pathway.

Can you take Tesamorelin and retatrutide together?

This falls outside the scope of published GH-axis secretagogue research and would depend on individual research design and professional guidance. We’re not able to advise on combining specific compounds.

Can women take Tesamorelin?

The FDA approval and clinical trial population behind Tesamorelin relate specifically to HIV-associated lipodystrophy. Questions about use outside that specific research context should be directed to a qualified healthcare professional rather than answered generally here.

Is CJC-1295 the same as Ipamorelin?

No. They’re frequently sold and researched together, but they’re structurally different peptides acting on different receptors. CJC-1295 is a GHRH receptor agonist, while Ipamorelin is a ghrelin receptor agonist. Their complementary mechanisms are why they’re often paired, not because they do the same thing.

How long does Tesamorelin stay in your system?

Tesamorelin has a short circulating half-life, which is why clinical trials studied it as a once-daily subcutaneous injection rather than a less frequent schedule. Its downstream effects on IGF-1 and visceral fat build over weeks of consistent use rather than persisting from a single dose.

Where can I buy these compounds in the UK?

River Peptides supplies all six as third-party tested research compounds. See our Ipamorelin, Tesamorelin and CJC-1295/Ipamorelin blend, plus Sermorelin, Hexarelin and GHRP-6 pages for full specifications and batch testing data.