Research goal
Covers compounds researched for growth hormone secretagogue activity, anabolic signalling, lean mass accretion, and body composition modulation.
| Compound | Class | Primary mechanism | Commonly reported for | Link |
|---|---|---|---|---|
| Ipamorelin | GHRP / Ghrelin mimetic | Selective GH release via ghrelin receptor; minimal cortisol/prolactin | Clean GH pulse stimulation, lean mass | View profile → |
| CJC-1295 | GHRH analogue | Extends endogenous GHRH signalling; sustained GH elevation | GH axis support, muscle growth protocols | View profile → |
| Tesamorelin | GHRH analogue | FDA-approved GHRH analogue; strong GH pulse; visceral fat reduction | GH stimulation, recomposition | View profile → |
| MK-677 | GH secretagogue (non-peptide) | Orally active ghrelin mimetic; sustained 24hr GH/IGF-1 elevation | Muscle mass, recovery, sleep quality | Profile coming soon |
| GHRP-2 | GHRP | Strong GH release; stimulates appetite significantly | GH pulse, mass protocols | Profile coming soon |
| GHRP-6 | GHRP | GH release via ghrelin receptor; pronounced appetite stimulation | Bulking protocols, GH axis | Profile coming soon |
Growth hormone secretion from the anterior pituitary is regulated by two opposing hypothalamic peptides: growth hormone-releasing hormone (GHRH), which stimulates pulsatile GH release, and somatostatin, which inhibits it. GHRH analogues such as CJC-1295 and tesamorelin amplify the GHRH signal at pituitary somatotroph cells, increasing the amplitude of endogenous GH pulses rather than generating continuous GH elevation. GHRPs — including ipamorelin, GHRP-2, and GHRP-6 — act primarily via the ghrelin receptor (GHS-R1a), increasing both GH pulse frequency and amplitude through a pathway distinct from GHRH. Research has investigated the combination of a GHRH analogue with a GHRP for its potential to produce synergistic GH release beyond what either compound achieves alone, a principle that underlies the most commonly studied secretagogue combinations.
GHRH analogues and GHRPs differ not only in receptor target but in the character of GH release they produce. GHRH analogues extend and amplify existing pulsatile GH secretion while preserving the negative feedback relationship with somatostatin, which limits the degree of GH elevation and reduces the risk of GH blunting over time. GHRPs, particularly GHRP-2 and GHRP-6, produce more robust acute GH pulses but may also stimulate cortisol and prolactin to varying degrees depending on the compound. Ipamorelin is notable in research for its relative selectivity — it produces GH release with minimal concurrent elevation of cortisol or prolactin, making it of interest for research contexts where hormonal side effects are a consideration. MK-677, a non-peptide ghrelin mimetic, achieves sustained 24-hour GH and IGF-1 elevation through oral administration, which distinguishes it from injectable peptide secretagogues.
The anabolic relevance of GH secretagogues is largely mediated through downstream IGF-1 production, primarily in the liver. Elevated GH stimulates hepatic IGF-1 synthesis, and circulating IGF-1 acts on skeletal muscle via the IGF-1 receptor to activate PI3K/Akt/mTOR signalling, a central pathway in muscle protein synthesis. IGF-1 also promotes satellite cell activation — the proliferation and differentiation of muscle stem cells in response to mechanical and hormonal signals — which underlies muscle hypertrophy and repair. Research has investigated GH secretagogues for their potential role in augmenting this axis in contexts of GH deficiency, ageing-related decline in GH pulsatility, or as adjuncts to resistance training, though human data on direct lean mass accretion in healthy populations remain limited relative to preclinical findings.
Ipamorelin is a pentapeptide GHRP that selectively stimulates GH release through the ghrelin receptor with a specificity profile that distinguishes it from earlier GHRPs. Research has investigated ipamorelin for its potential role in GH pulse stimulation without the cortisol or prolactin elevation commonly associated with GHRP-2 or GHRP-6, making it of particular interest in research contexts where hormonal selectivity matters. It is most commonly studied in combination with a GHRH analogue such as CJC-1295, where the two pathways are proposed to act synergistically. Commonly reported doses range from 100 mcg to 300 mcg per administration in research settings. Anecdotal reports suggest improvement in recovery and sleep quality alongside lean mass changes over multi-week protocols.
CJC-1295 is a GHRH analogue modified with a drug affinity complex (DAC) that enables binding to serum albumin, significantly extending its half-life compared to native GHRH. Research has investigated CJC-1295 for its potential role in sustaining elevated GH and IGF-1 levels over longer inter-dose intervals than short-acting GHRH peptides permit. The extended half-life means it can be dosed less frequently while maintaining a raised GH baseline, which research suggests may support lean mass changes, fat reduction, and recovery over time. Commonly reported doses range from 1 mg to 2 mg weekly in research protocols, often combined with a GHRP such as ipamorelin. Anecdotal reports suggest improvement in body composition and sleep quality over protocols of 12 weeks or longer.
Tesamorelin is a synthetic GHRH analogue approved by the FDA for the reduction of excess abdominal fat in HIV-associated lipodystrophy, representing one of the few GH secretagogues with established clinical trial data in humans. Research has investigated tesamorelin for its potential role in stimulating pulsatile GH release with downstream IGF-1 elevation, and separately for its effects on visceral adipose tissue reduction independent of lean mass changes. Its clinical approval provides a more robust data foundation than most research peptides in this class. Commonly reported doses in research settings are 1 mg to 2 mg administered subcutaneously daily. Reported side effects in research and anecdotal accounts include injection site reactions, fluid retention, and joint discomfort consistent with GH elevation.
MK-677 (ibutamoren) is a non-peptide, orally active ghrelin mimetic that achieves sustained GH and IGF-1 elevation over a 24-hour period following a single daily dose. Research has investigated MK-677 for its potential role in increasing lean body mass, improving bone density, and enhancing sleep architecture, with human clinical trial data available across multiple populations. Its oral bioavailability distinguishes it from all injectable peptide secretagogues in this class, and its ability to sustain elevated IGF-1 for extended periods is of interest in longitudinal research contexts. Commonly reported doses range from 10 mg to 25 mg orally per day. Reported side effects in research and anecdotal accounts include increased appetite, transient fluid retention, and mild insulin resistance at higher doses.
GHRP-2 is a synthetic hexapeptide that acts as a potent ghrelin receptor agonist, producing robust GH pulses and is among the strongest GHRPs in terms of acute GH release. Research has investigated GHRP-2 for its potential role in GH axis stimulation, with human studies confirming significant GH pulse generation following subcutaneous or intravenous administration. Unlike ipamorelin, GHRP-2 produces meaningful cortisol and prolactin elevation alongside GH release, a profile that is relevant in research designs sensitive to glucocorticoid or prolactin confounders. Commonly reported doses range from 100 mcg to 300 mcg per administration. GHRP-2 is often studied in combination with GHRH analogues for synergistic GH release and in mass-phase research protocols where appetite stimulation is considered acceptable.
GHRP-6 is a hexapeptide GHRP with a pronounced appetite-stimulating effect that distinguishes it from later-generation GHRPs such as ipamorelin. Research has investigated GHRP-6 for its potential role in GH secretion and as an early reference compound in ghrelin receptor research, with its appetite stimulation arising from central ghrelin receptor activation in hypothalamic feeding circuits. This appetite effect is frequently noted in anecdotal research reports and is a practical consideration in research designs involving caloric intake monitoring. Commonly reported doses range from 100 mcg to 300 mcg per administration, typically three times daily timed to avoid feeding. Reported side effects in research and anecdotal accounts include pronounced hunger, light-headedness, and in some cases cortisol and prolactin elevation.
The most widely documented secretagogue combination in research literature. CJC-1295 provides sustained GHRH-pathway stimulation and elevated GH baseline via albumin binding, while ipamorelin adds pulsatile GH release through the ghrelin receptor with a clean hormonal profile. The dual-pathway approach is proposed to produce synergistic GH output beyond what either compound achieves independently, making this the reference combination for GH-axis-focused muscle growth research.
How do GHRH analogues and GHRPs differ in the way they drive GH release?
GHRH analogues such as CJC-1295 and tesamorelin act at the pituitary GHRH receptor, amplifying the amplitude of endogenous GH pulses. They work within the existing somatostatin feedback system, which prevents excessive GH elevation and helps preserve normal pulsatility. GHRPs such as ipamorelin, GHRP-2, and GHRP-6 act at the ghrelin receptor, increasing both pulse frequency and amplitude through a distinct and partially independent pathway. Because the two pathways converge on the pituitary somatotroph via different receptors, their combination is proposed to produce a synergistic increase in GH output greater than additive effects from either class alone.
How long do research protocols for GH secretagogues typically run?
Clinical and research protocols for GH secretagogues have commonly run for 12 to 24 weeks in human studies, reflecting the time required for IGF-1 to stabilise and for measurable changes in lean body mass or fat distribution to emerge. Anecdotal research reports frequently describe protocols of 12 to 16 weeks, with some longer-term protocols extending to 6 months or beyond for body composition endpoints. Tesamorelin trials have used 26-week endpoints for visceral fat outcomes. The duration is typically determined by the physiological outcome under investigation and the rate at which meaningful changes can be detected against baseline variance.
Do these compounds directly stimulate muscle tissue, or do they act upstream via GH and IGF-1?
GH secretagogues — including GHRH analogues, GHRPs, and MK-677 — act upstream of muscle tissue rather than directly on it. Their primary target is the pituitary gland, where they stimulate endogenous GH release. GH then signals the liver to produce IGF-1, which circulates systemically and acts on muscle via the IGF-1 receptor to activate anabolic signalling cascades including PI3K/Akt/mTOR and satellite cell activation. These compounds do not directly stimulate muscle protein synthesis or myogenesis; their anabolic relevance is entirely mediated through the GH/IGF-1 axis. This distinction has practical implications for research designs that aim to isolate the site and mechanism of anabolic effect.
What is the rationale for combining CJC-1295 and Ipamorelin in research protocols?
The combination targets two distinct receptor pathways that converge on pituitary GH release. CJC-1295 extends the GHRH signal through albumin binding, raising the GH pulse baseline and sustaining elevated IGF-1 between doses. Ipamorelin adds pulsatile GH stimulation through the ghrelin receptor without the cortisol or prolactin elevation associated with older GHRPs. Research has investigated this combination for its potential to produce synergistic GH and IGF-1 elevation while maintaining a relatively clean hormonal profile. The pairing is the most commonly reported secretagogue combination in anecdotal and research literature on GH-axis-based muscle growth and recomposition protocols.