CJC-1295 and Ipamorelin are supplied strictly as laboratory research materials. They are not approved, intended or authorised for human consumption or any therapeutic use in this context. This article is written for qualified researchers and is not medical advice.
Two levers on the same axis
The growth hormone axis has two natural inputs, and these two peptides act on one each. Growth hormone-releasing hormone (GHRH) tells the pituitary how much GH to make and release; ghrelin, acting through a separate receptor, sets the timing and size of each pulse. CJC-1295 is a synthetic GHRH analogue — it pulls the first lever. Ipamorelin is a selective ghrelin-mimetic GHRP — it pulls the second. That single distinction explains almost everything that follows, including why the honest answer to "which one" is often "both". Before the table, it helps to hold onto the framing that these are complementary tools, not competing ones.
| CJC-1295 | Ipamorelin | |
|---|---|---|
| Class / peptide type | GHRH analogue (29 aa) | Selective GHRP / ghrelin-mimetic (pentapeptide) |
| Primary receptor | GHRH-R (anterior pituitary) | GHS-R1a (ghrelin receptor) |
| Signalling | Gs → cAMP / PKA | Gq → phospholipase C / Ca²⁺ |
| Structure / MW | ~3647 g/mol (no DAC); modified at positions 2, 8, 15, 27 | 711.9 g/mol; Aib-His-D-2Nal-D-Phe-Lys-NH₂ |
| Half-life / duration | ~30 min (no DAC) · 5.8–8.1 days (with DAC) | ~2 hours (IV) |
| Main research focus | Sustained GH/IGF-1 elevation, pituitary output | Selective GH pulse without cortisol/prolactin rise |
| Regulatory status | Not FDA-approved; research reagent | Not FDA-approved; WADA S2 prohibited |
CJC-1295: the GHRH signal
CJC-1295 is a 29-amino acid analogue of GHRH, engineered at four positions — 2, 8, 15 and 27 — to resist the enzymatic degradation that clears native GHRH within minutes. Its target is the GHRH receptor on somatotroph cells of the anterior pituitary, where binding activates a Gs protein, raises intracellular cAMP and drives protein kinase A. The downstream effect is twofold: enhanced GH gene transcription and stimulated release of GH pulses, followed by hepatic elevation of IGF-1. Because GHRH-receptor expression is largely restricted to the pituitary, CJC-1295 behaves as a comparatively targeted probe of pituitary-driven GH signalling.
Kinetics are where the two versions of the molecule diverge sharply. The plain form — Mod GRF (1-29), without the Drug Affinity Complex — carries a half-life of roughly 30 minutes. The DAC variant binds covalently to circulating albumin, stretching the half-life to between about 5.8 and 8.1 days and holding IGF-1 above baseline for far longer after repeated dosing. In research terms, CJC-1295 is the compound you reach for when the question is about sustained GHRH-receptor stimulation and total pituitary output. For the full mechanistic detail, see the CJC-1295 knowledgebase profile, or go straight to buy CJC-1295 UK for research-grade material.
Ipamorelin: the selective pulse
Ipamorelin is a synthetic pentapeptide developed by Novo Nordisk in the late 1990s and is widely regarded as the first GHS-receptor agonist with GH-release selectivity comparable to endogenous GHRH. It binds GHS-R1a — the ghrelin receptor — activating phospholipase C and mobilising intracellular calcium in somatotrophs to produce a discrete, time-limited GH pulse. It also suppresses somatostatin, GH's inhibitory signal, acting on both arms of GH regulation at once.
Its defining property is what it doesn't do. Earlier GHRPs such as GHRP-6 and GHRP-2 reliably dragged cortisol and ACTH up alongside GH, confounding study designs. Ipamorelin, by contrast, produces robust GH pulses without meaningful co-stimulation of cortisol, prolactin, ACTH, FSH, LH or TSH — even at doses far above its GH-releasing threshold. That clean selectivity is precisely why it is favoured in research paradigms that need isolated GH-axis stimulation without adrenocortical noise. With a short ~2-hour IV half-life, it delivers a sharp pulse rather than sustained elevation. Researchers can review the Ipamorelin knowledgebase profile or source Ipamorelin research material directly.
What the differences mean in a research context
Set the two profiles side by side and the contrast is one of class, not quality. CJC-1295 sets the ceiling — it signals the pituitary to synthesise and release GH via the cAMP/PKA cascade, and in its DAC form it does so for days. Ipamorelin sets the shape of the pulse — a fast, selective, calcium-driven release through the ghrelin receptor, with somatostatin held down at the same time. They engage separate receptor populations through separate intracellular pathways that converge only at the point of GH secretion.
That separation is exactly why the field studies them together. Preclinical porcine work (Jørgensen et al., 2001) found that co-administering a GHRH analogue with a GHS-receptor agonist produced GH responses roughly 2–4× greater than either compound alone — a genuine synergy, not simple addition. The GHRH arm raises the amount of GH available and primes the somatotroph; the GHRP arm triggers its release and lifts the inhibitory brake. Read that way, "CJC-1295 vs Ipamorelin" is slightly the wrong question. The more useful framing is complementary: they are the two halves of a dual-pathway protocol, which is how they most often appear in GH-axis research.
Where a genuine either/or does apply is scope. If a study needs sustained IGF-1 elevation and a probe of pituitary synthetic capacity, CJC-1295 — particularly the DAC variant — is the tool. If it needs a clean, isolated GH pulse free of cortisol and prolactin confounders, Ipamorelin is the more selective instrument. Neither is FDA-approved; both are supplied only as research reagents, and Ipamorelin additionally sits on WADA's Prohibited List (S2).
The bottom line
CJC-1295 and Ipamorelin are not competitors so much as counterparts: one is the GHRH signal that builds GH, the other the selective ghrelin-mimetic pulse that releases it. Choose CJC-1295 for sustained, GHRH-driven output; choose Ipamorelin for a clean, cortisol-sparing pulse — and note that the published data makes the strongest case for running them as a pair. For research-grade material with ≥99% purity and a COA, see our pages to buy CJC-1295 UK and buy Ipamorelin UK.