Growth hormone secretagogues stimulate the pituitary to release its own GH — as opposed to injecting recombinant GH directly. They work through two receptor pathways (GHRH and ghrelin) that produce synergistic effects when activated together, which is why combination protocols dominate clinical practice. The core tension in this space: the most popular combination (CJC-1295 no-DAC + ipamorelin) has zero published trial data, while the only FDA-approved option — tesamorelin — has Phase III evidence across 816 patients⁶ ⁷.
At a Glance
| Compound | Pathway | Half-Life | Evidence | Reg. Status | Best For |
|---|---|---|---|---|---|
| Tesamorelin | GHRH-R | 8-38 min | Phase III RCTs (N=816) | FDA-approved (HIV lipodystrophy) | Visceral fat reduction (strongest evidence) |
| Anamorelin | GHS-R1a | 7-12 hr | Phase III (ROMANA 1&2) | Japan only (cachexia) | Cancer-related cachexia |
| Macimorelin | GHS-R1a | ~4.1 hr | Phase III (diagnostic) | FDA-approved (diagnostic) | GH deficiency diagnosis only |
| Sermorelin | GHRH-R | 10-20 min | Phase III (pediatric) | Withdrawn 2008 (manufacturing) | Legal defensibility for compounding |
| MK-677 | GHS-R1a | ~24 hr | 2-year RCT (N=65) | Research chemical | Oral dosing without injections |
| CJC-1295 DAC | GHRH-R | 5.8-8.1 days | Phase I/II | Never approved | Weekly dosing convenience |
| Ipamorelin | GHS-R1a | ~2 hr | Phase II (failed efficacy) | Regulatory limbo | Clean GH release without off-target effects |
| GHRP-2 | GHS-R1a | 25-55 min | Phase I/PK studies | Never approved | Raw GH potency (non-selective) |
| GHRP-6 | GHS-R1a | ~20 min | Phase I/PK studies | Never approved | GH release with appetite stimulation |
| Hexarelin | GHS-R1a | 50-71 min | Small human studies | Never approved | Strongest acute GH spike (short-term only) |
| CJC-1295 no-DAC | GHRH-R | ~30 min | Zero human trials | Regulatory limbo | Combination protocols (by popularity, not evidence) |
The Compounds
Tesamorelin
The evidence leader among secretagogues, and it isn't close. Tesamorelin is the only compound in this class with Phase III RCT data — two trials enrolling over 800 HIV patients demonstrated 15-20% visceral fat reduction⁶ ⁷. Its trans-3-hexenoic acid modification gives it better enzymatic stability than sermorelin, and its full 44-amino-acid sequence is more physiologically representative than sermorelin's truncated 29-amino-acid chain.
The catch is durability. VAT regains rapidly (+24.5%) when you stop⁷. This is a continuous-use compound, and the FDA indication is narrow: HIV-associated lipodystrophy. Whether those visceral fat reduction numbers translate to non-HIV populations hasn't been tested at Phase III scale. For a full breakdown, see our tesamorelin deep dive.
Sermorelin
The first FDA-approved GHRH analog, sermorelin earned its approval in 1997 for pediatric GH deficiency and was withdrawn in 2008 — for manufacturing reasons, not safety¹. That distinction matters: prior FDA approval gives sermorelin the clearest legal standing of any secretagogue for compounding under the 503A framework⁹.
Adult body composition data is thin. The key study is Khorram 1997, which showed improvements in body composition and exercise tolerance in 19 elderly subjects over a two-year follow-up⁸. That's it for adult clinical evidence. Sermorelin's value proposition is regulatory, not evidentiary — it's the secretagogue you can most confidently source from a compounding pharmacy without legal ambiguity. For the full regulatory picture, see our sermorelin guide.
Ipamorelin
Ipamorelin's defining feature is what it doesn't do. In the 1998 Raun study — conducted in swine, not humans — it released GH without elevating cortisol, ACTH, or prolactin even at doses 200 times the GH-effective threshold¹⁰. No other ghrelin-pathway agent comes close to that selectivity profile.
The efficacy story is less impressive. Ipamorelin's only clinical efficacy trial — a Phase II study for postoperative ileus — failed to show benefit over placebo¹¹. People use ipamorelin for its safety data, not its efficacy data. And the selectivity data that drives its popularity comes from animal models, which don't always predict human pharmacology. Still, the absence of off-target effects at extreme doses is a meaningful signal that separates ipamorelin from its older, messier cousins in the ghrelin-receptor class.
CJC-1295
The nomenclature problem is the story here. "CJC-1295" refers to two compounds with the same name and radically different pharmacology.
CJC-1295 with DAC has a Drug Affinity Complex that binds albumin, producing a half-life of 5.8-8.1 days — a single injection sustains GH and IGF-1 elevation for over a week¹² ¹³. It reached Phase I/II trials before development halted in 2006 after a patient death attributed to pre-existing coronary disease, not the compound¹⁴. All published human data labeled "CJC-1295" used this version.
CJC-1295 without DAC (Modified GRF 1-29) lacks the albumin-binding complex entirely, giving it a half-life of roughly 30 minutes⁵. It has zero published human trial data. Its pharmacology is extrapolated from the DAC variant and from GHRH analog class membership. Despite this, it's one of the most widely available compounds in the compounding market — largely because it pairs well with ipamorelin in combination protocols based on the synergy principle.
MK-677
The only orally bioavailable secretagogue with substantial clinical data. A 2-year RCT in 65 healthy older adults showed MK-677 (25 mg daily) restored GH and IGF-1 to youthful levels and increased fat-free mass by 1.1 kg versus placebo (P<0.001)¹⁵. It also produced a notable sleep signal in earlier studies: 50% increase in Stage 4 slow-wave sleep and greater than 20% increase in REM duration¹⁷.
The trade-offs are real. Lean mass gains produced no measurable improvement in strength or physical function¹⁵. Side effects include transient appetite increase, peripheral edema, ~5 mg/dL fasting glucose rise, and ~1.7 mcg/dL cortisol elevation¹⁵. MK-677 is a small molecule, not a peptide — which places it outside peptide compounding regulations under different regulatory treatment. Merck abandoned development.
The remaining compounds serve narrower roles. GHRP-2 and GHRP-6 are potent GH releasers but non-selective — both elevate cortisol and prolactin, and GHRP-6 in particular drives strong appetite¹⁶. Hexarelin produces the strongest acute GH response of any secretagogue but develops tachyphylaxis rapidly, limiting practical use¹⁶. Anamorelin gained Japan-only approval for cancer cachexia but was rejected by the EMA for failing to demonstrate functional improvements¹⁹. Macimorelin is FDA-approved solely as a diagnostic tool for GH deficiency.
Selectivity Comparison
The dimension that matters most for protocol design is selectivity — whether a compound triggers only GH release or also activates cortisol, prolactin, and appetite.
| Compound | Cortisol | Prolactin | Appetite | Water Retention |
|---|---|---|---|---|
| Ipamorelin | None (at >200x dose) | None | None | Minimal |
| Sermorelin | None | Small acute rise | None | Minimal |
| Tesamorelin | None reported | None reported | None | Minimal |
| CJC-1295 no-DAC | No data | No data | No data | No data |
| CJC-1295 DAC | None reported | None reported | None | Moderate (sustained GH elevation) |
| MK-677 | +1.7 mcg/dL | Not significant | Moderate (transient) | Moderate |
| GHRP-2 | Transient increase | Modest increase | Strong (dose-dependent) | Moderate |
| GHRP-6 | Transient increase | Modest increase | Strong (ghrelin mimicry) | Moderate |
| Hexarelin | Significant increase | Significant increase | Mild-moderate | Moderate |
Sources: ¹⁰ ¹⁵ ¹⁶ ¹⁷
Combinations and Synergy
Why combine two secretagogues instead of using one at a higher dose? Because the two receptor pathways aren't just additive — they're synergistic. A GHRH analog plus a ghrelin-receptor agonist produces a GH response that exceeds what either compound achieves alone, through convergent intracellular signaling.
The GHRH pathway (sermorelin, tesamorelin, CJC-1295) activates the GHRH receptor via cAMP/PKA signaling, telling pituitary somatotrophs to release stored GH and produce more¹ ². This pathway respects somatostatin feedback — when GH rises, the hypothalamus applies the brake². The ghrelin pathway (ipamorelin, GHRP-2, MK-677) activates GHS-R1a via PLC/PKC signaling, acting both directly on the pituitary and indirectly through hypothalamic neurons³ ⁴. When both cascades converge on the same somatotroph cell simultaneously, the intracellular response amplifies beyond what either pathway generates alone.
Combined activation produces synergistic GH release — a more physiologically robust pulse pattern than either pathway alone. Bowers et al. (1990) established the principle: submaximal doses of GHRP combined with GHRH produced synergistic, not merely additive, GH release in healthy men³. Veldhuis and Bowers (2009) quantified the magnitude — GHRP-2 alone produced a 47-fold increase in pulsatile GH secretion, GHRH alone a 20-fold increase, and the combination a 54-fold increase (versus a theoretical additive 67-fold), optimizing pulse amplitude and frequency in ways neither pathway achieves independently⁴.
The two common pairings in practice are CJC-1295 no-DAC + ipamorelin and sermorelin + ipamorelin — both pairing a GHRH analog with the cleanest ghrelin-pathway agent.
There's a critical caveat. The same Veldhuis 2009 study showed that synergy magnitude declines approximately 55% in older men with low testosterone, higher visceral fat, and reduced IGF-1⁴. Together, abdominal visceral fat, IGF-1, and IGFBP-3 explained 60% of the variability in synergy magnitude (P<0.001)⁴. The people most likely to seek GH peptides — older adults with declining GH and increasing belly fat — are the population in whom synergy is most blunted. It doesn't vanish, but expectations should be calibrated.
One more mechanistic constraint: ghrelin-pathway agents require intact GHRH signaling. GHRH-knockout models show markedly attenuated responses to GHRP-2, confirming that the ghrelin pathway depends on endogenous GHRH tone³ ⁴. Patients with severe hypothalamic dysfunction may not respond fully to ghrelin-mimetic compounds alone.
The Evidence Gap
The most widely used combination — CJC-1295 without DAC plus ipamorelin — has zero peer-reviewed human trial data as a paired protocol⁵ ¹⁸.
The evidence supporting this protocol rests on three legs:
- The general GHRH + GHRP synergy principle — strong, backed by Bowers 1990, Veldhuis 2009, and decades of basic science³ ⁴
- Individual compound pharmacology — moderate for ipamorelin (PK/PD data exist), weak for CJC-1295 no-DAC (inferred from the DAC variant and GHRH analog class)
- Clinical practice experience — anecdotal, widely used by optimization clinicians, but no systematic pharmacovigilance data published
The only published combination study is Sigalos et al. (2017)¹⁸: sermorelin + GHRP-2 + GHRP-6 in 14 hypogonadal men already on testosterone. Mean IGF-1 rose from 159.5 to 239.0 ng/mL (P<0.0001) over approximately 134 days¹⁸. Encouraging — but retrospective, with only 14 compliant patients out of 105 enrolled, no body composition endpoints, and results confounded by concurrent testosterone¹⁸. A different combination from what most people now use, with older, less selective compounds.
The gap exists because there's no commercial incentive for combination trials. Tesamorelin generates pharmaceutical revenue; compounded peptide combinations don't attract the investment needed for large RCTs. The clinical community has run a massive, undocumented open-label experiment based on mechanistic reasoning. That reasoning is sound — but "mechanistically sound" and "clinically proven" are different standards.
Regulatory Landscape
Sermorelin has the clearest legal standing. Prior FDA approval (1997) qualifies it for compounding under the 503A framework regardless of the FDA's current bulks list categorization⁹. Its withdrawal was a business decision, not a safety action.
CJC-1295 and ipamorelin followed a turbulent path. The FDA initially placed both in Category 2 (safety concerns, not compoundable) in 2024. That September, they were removed from Category 2 after nominators withdrew²⁰. Removal from the banned list didn't place them on the approved list. As of early 2026, both exist in regulatory limbo — not explicitly prohibited, but not on the 503A Bulks List. The PCAC reviewed ipamorelin and ibutamoren in October 2024 and recommended neither be added²⁰.
MK-677 faces a different regulatory framework entirely as a non-peptide small molecule, sold as a research chemical and sometimes appearing as an adulterant in dietary supplements¹⁵.
The enforcement trend is clear. The FDA issued warning letters to multiple peptide suppliers in December 2024, and over 40 state attorneys general co-signed a letter demanding a federal crackdown on compounded peptides²⁰. That initiative centered on GLP-1 agonists, but the regulatory infrastructure being built has implications across all compounded secretagogues.
| Compound | Regulatory Risk (US) | Rationale |
|---|---|---|
| Sermorelin | Low | Prior FDA approval; clear 503A pathway |
| Tesamorelin | Low (branded) | FDA-approved (Egrifta); compounding may face brand objection |
| CJC-1295 no-DAC | Medium-High | No FDA history; regulatory limbo |
| Ipamorelin | Medium-High | PCAC declined recommendation; limbo |
| MK-677 | High | Non-peptide; research chemical; supplement fraud concerns |
Frequently Asked Questions
What is the best GH peptide for beginners?
Ipamorelin is the most common starting point because of its uniquely clean selectivity profile — it releases growth hormone without triggering cortisol, prolactin, or appetite changes, even at doses far above what's needed for GH stimulation. For the GHRH pathway, sermorelin has the strongest legal standing due to its prior FDA approval and clear 503A compounding pathway. Many clinicians start with one of these before considering combination protocols.
What is the difference between CJC-1295 with DAC and without DAC?
They are fundamentally different compounds despite sharing a name. CJC-1295 with DAC has a Drug Affinity Complex that binds to albumin, producing a half-life of 5.8–8.1 days and sustained GH elevation from a single injection. CJC-1295 without DAC (Modified GRF 1-29) lacks this complex, giving it a half-life of roughly 30 minutes — meaning it requires daily injection.
Critically, all published human clinical data labeled "CJC-1295" used the DAC version. CJC-1295 without DAC has zero published human trial data. Its pharmacology is entirely extrapolated from the DAC variant and from GHRH analog class membership.
How does ipamorelin compare to sermorelin?
They work through different receptor pathways and are complementary rather than competitive. Sermorelin activates the GHRH receptor (cAMP/PKA pathway), while ipamorelin activates the ghrelin receptor (PLC/PKC pathway). Ipamorelin's advantage is its unmatched selectivity — no cortisol, ACTH, or prolactin elevation even at extreme doses. Sermorelin's advantage is regulatory: its prior FDA approval makes it the most legally defensible secretagogue for compounding.
In combination protocols, the two are often used together precisely because they activate different pathways. The GHRH + GHRP synergy principle — demonstrated by Veldhuis and Bowers — shows that simultaneous activation of both pathways produces greater GH release than either alone.
Can you take GH peptides with GLP-1 drugs?
There is no published clinical data on combining GH secretagogues with GLP-1 receptor agonists like semaglutide or tirzepatide. The mechanisms are pharmacologically distinct — GH secretagogues act on pituitary GH release while GLP-1 drugs act on incretin receptors — so a direct interaction is unlikely. However, some GH secretagogues (particularly GHRP-2, GHRP-6, and MK-677) increase appetite and can raise fasting glucose, which could work against GLP-1 goals. Ipamorelin and GHRH-pathway compounds do not have these effects, making them more compatible in theory. Discuss any combination with a prescribing clinician.
Do GH peptides show up on drug tests?
Most standard employment drug panels do not test for peptides. However, WADA (World Anti-Doping Agency) prohibits all growth hormone secretagogues in competitive sport, and specialized anti-doping tests can detect GH peptide metabolites. MK-677 is particularly detectable due to its long 24-hour half-life and small-molecule structure. Ipamorelin and GHRP-2 have also been identified in doping control analyses. Anyone subject to athletic anti-doping testing should assume all GH secretagogues are banned and detectable.
How long until you see results from GH peptides?
The timeline depends on what you're measuring. Acute GH release occurs within minutes of injection — blood tests will show elevated GH and, over days, rising IGF-1 levels. Subjective effects like improved sleep quality and recovery may appear within the first 1–2 weeks. Body composition changes (fat loss, lean mass) require months of consistent use. Tesamorelin's Phase III trials measured visceral fat reduction over 26 weeks. MK-677's 2-year RCT showed a 1.1 kg increase in fat-free mass — meaningful but modest, and notably without corresponding strength or functional improvements.
Is there an oral GH peptide option?
MK-677 (ibutamoren) is the only orally bioavailable GH secretagogue with long-term clinical data. It has a 24-hour half-life allowing once-daily dosing at 25 mg. A 2-year RCT showed it restored GH and IGF-1 to youthful levels and increased fat-free mass. The trade-offs: transient appetite increase, peripheral edema, modest fasting glucose rise, and cortisol elevation. Lean mass gains did not translate into strength or functional improvements. MK-677 is technically a small molecule, not a peptide, which places it under different regulatory treatment than peptide secretagogues.
What is the best GH peptide combination or stack?
The most widely used combination is CJC-1295 without DAC plus ipamorelin — a GHRH analog paired with a selective ghrelin-receptor agonist. The pharmacological rationale is sound: the two pathways (cAMP/PKA and PLC/PKC) produce synergistic GH release when activated simultaneously, as demonstrated by Veldhuis and Bowers.
However, this specific combination has zero published human trial data. The only published combination study (Sigalos 2017) used sermorelin + GHRP-2 + GHRP-6 in 14 men and showed significant IGF-1 elevation. The general synergy principle is well-established, but the particular pairings people use are extrapolated, not directly proven. Also worth noting: synergy magnitude declines with age and body fat — older adults with higher visceral fat showed only 45% of the synergistic response seen in younger men.
References
¹ Sermorelin for adult GH insufficiency — Walker RF. "Sermorelin: a better approach to management of adult-onset growth hormone insufficiency?" Clinical Interventions in Aging. 2006;1(4):307-308. PubMed 18046908
² Sermorelin endogenous GH release — Walker RF. "Sermorelin: stimulation of endogenous GH release." In: Growth Hormone Secretagogues. 2006. PubMed 18046908
³ GHRP pituitary activity discovery — Bowers CY et al. "On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone." Journal of Clinical Endocrinology & Metabolism. 1990;70(4):975-982. PubMed 2108187
⁴ GHRH + GHRP synergy determinants — Veldhuis JD, Bowers CY. "Determinants of joint GH-releasing hormone and GH-releasing peptide synergy in man." American Journal of Physiology -- Endocrinology and Metabolism. 2009;296(5):E1085-E1092. PubMed 19240251
⁵ GH secretagogues in hypogonadal body composition — Sinha DK et al. "Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males." Translational Andrology and Urology. 2020;9(Suppl 2):S149-S159. PMC7108996
⁶ Tesamorelin Phase III in HIV — Falutz J et al. "Metabolic Effects of a Growth Hormone-Releasing Factor in Patients with HIV." New England Journal of Medicine. 2007;357:2359-2370. DOI
⁷ EGRIFTA prescribing information — FDA Prescribing Information, EGRIFTA (tesamorelin). 2019. FDA Label
⁸ Sermorelin body composition in elderly — Khorram O et al. "Two-year follow-up of a study on GHRH analog administration in elderly adults." Clinical Endocrinology. 1997;47:97-106.
⁹ Peptide compounding regulatory status — Frier Levitt. "Regulatory Status of Peptide Compounding in 2025." 2025. Frier Levitt
¹⁰ Ipamorelin selectivity discovery — Raun K et al. "Ipamorelin, the first selective growth hormone secretagogue." European Journal of Endocrinology. 1998;139(5):552-561. PubMed 9849822
¹¹ Ipamorelin Phase II postoperative ileus — Helsinn Therapeutics. Phase II study of ipamorelin for postoperative ileus. NCT00672074.
¹² CJC-1295 prolonged GH stimulation — Teijeiro R et al. "Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults." Journal of Clinical Endocrinology & Metabolism. 2006;91(3):799-805. PubMed 16352683
¹³ CJC-1295 pulsatile GH persistence — Ionescu M, Bhatt DL. "Pulsatile secretion of growth hormone persists during continuous stimulation by CJC-1295." Journal of Clinical Endocrinology & Metabolism. 2006;91:4792-4797. PubMed 17018654
¹⁴ CJC-1295 trial discontinuation — ConjuChem Biotechnologies. CJC-1295 Phase II trial discontinuation. 2006.
¹⁵ MK-677 two-year RCT in older adults — Nass R et al. "Effects of an Oral Ghrelin Mimetic on Body Composition and Clinical Outcomes in Healthy Older Adults: A Randomized Trial." Annals of Internal Medicine. 2008;149(9):601-611. PMC2757071
¹⁶ Ghrelin vs hexarelin vs GHRH comparison — Arvat E et al. "Endocrine activities of ghrelin, a natural growth hormone secretagogue, in humans: comparison and interactions with hexarelin, a nonnatural peptidyl GH secretagogue, and GH-releasing hormone." Journal of Clinical Endocrinology & Metabolism. 1997;82:3734-3740. PubMed 9285939
¹⁷ GH secretagogue safety and efficacy review — Sigalos JT, Pastuszak AW. "The Safety and Efficacy of Growth Hormone Secretagogues." Sexual Medicine Reviews. 2018;6(1):45-53. PubMed 28400207 / PMC5632578
¹⁸ GH secretagogue combo raises IGF-1 — Sigalos JT et al. "Growth Hormone Secretagogue Treatment in Hypogonadal Men Raises Serum Insulin-Like Growth Factor-1 Levels." American Journal of Men's Health. 2017;11(6):1752-1757. PubMed 28830317 / PMC5675260
¹⁹ Anamorelin Japan approval for cachexia — Wakabayashi H et al. "The regulatory approval of anamorelin for treatment of cachexia in patients with non-small cell lung cancer, gastric cancer, pancreatic cancer, and colorectal cancer in Japan: facts and numbers." Journal of Cachexia, Sarcopenia and Muscle. 2021;12(1):14-16. PMC7890143
²⁰ Peptides removed from FDA Category 2 — Alpha Rejuvenation. "Peptides No Longer on FDA Category 2 List." 2024. Alpha Rejuvenation
Medical Disclaimer
The content in this protocol guide is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider before beginning any new protocol, supplement, or medication.