SIDE BY SIDE
Four answers, one question
Same target, four different theories of how to hit it. Compared on the things that actually differ: which receptor, what the pulse looks like afterwards, how long it lasts, and how strong the evidence really is.
Start here
All four compounds on this site are trying to make the pituitary release more growth hormone. None of them supplies growth hormone directly. Where they part company is how they ask.
Two of them — sermorelin and CJC-1295 — copy the brain's own instruction, GHRH. One of them, ipamorelin, uses an entirely different doorway, the one the hunger hormone ghrelin uses. The fourth is not a compound at all but a pairing that uses both doorways at once.
The second difference is time. Sermorelin lasts minutes. Ipamorelin lasts a couple of hours. CJC-1295 in its albumin-bound form lasts days. Because growth hormone naturally comes in short bursts, how long a compound lasts changes what the resulting pattern looks like — a quick prod produces a spike, a week-long prod raises the whole baseline.
The third difference, and the one that matters most for anyone reading claims online, is evidence. These four are not equally supported. One has a real controlled outcome in humans; one has a controlled trial that failed; one has a strong mechanism and hormone measurements; one has never been tested as sold. The table below keeps those apart.
The comparison table
| Ipamorelin | CJC-1295 | Sermorelin | CJC-1295 / Ipamorelin | |
|---|---|---|---|---|
| Class | Selective GHRP / ghrelin-receptor agonist | Long-acting GHRH analogue | Native GHRH fragment | GHRH analogue + GHRP pairing |
| Receptor | GHS-R1a (Gq, calcium) | GHRH receptor (Gs, cAMP) | GHRH receptor (Gs, cAMP) | Both, simultaneously |
| Structure | Pentapeptide, protease-resistant D-amino acids | hGRF(1–29) + 4 substitutions ± albumin hook | Unmodified GHRH(1–29) | The two above, co-administered |
| Duration | Terminal half-life ~2 h [4] | 5.8–8.1 days for the DAC form [11]; ~30 min for no-DAC | Minutes | Two mismatched clocks at once |
| Effect on the pulse | One discrete pulse peaking ~40 min post-dose [4] | Raises the basal floor ~7.5-fold; pulse frequency and magnitude unchanged [12] | Leaves shape to the pituitary; feedback fully intact [15] | Intended raised floor plus a sharp beat; uncharacterised in practice |
| Selectivity | No meaningful ACTH, cortisol or prolactin rise even far above the GH ED50 [6] | GHRH-receptor specific | GHRH-receptor specific; small transient rises in other pituitary hormones reported | Inherits both profiles |
| Best human evidence | Phase 2 RCT in 114 adults — missed primary endpoint [3] | Hormone kinetics in healthy adults [11][12] | Height velocity ~4.1 → ~7–8 cm/yr in GH-deficient children [16] | None for the blend; read-across only [17][18] |
| Endpoint type | Clinical (negative) | Surrogate (GH, IGF-1, proteome) | Clinical (growth), plus editorial argument | Borrowed |
| Regulatory status | Never approved; off the 503A Category 2 list, PCAC-reviewed 2024 | Never approved; not recommended for 503A bulks, 2024 | Previously FDA-approved, withdrawn 2008 for commercial reasons; Category 1 bulk under interim 503A policy | Neither component approved; Category 2 added 2023, removed 2024 |
| Sport | WADA S2, prohibited at all times | WADA S2, prohibited at all times | Prohibited; GHRH-analogue assays exist | Both S2, possibly S0 |
How they differ in mechanism
The cleanest way to see the split is at the level of second messengers. Pituitary somatotrophs carry two independent release triggers: the GHRH receptor signalling through Gs and cAMP, and GHS-R1a signalling through Gq and intracellular calcium. Sermorelin and CJC-1295 are both GHRH-receptor agents and therefore differ from each other only in pharmacokinetics, not in pathway. Ipamorelin is the only compound here on the other pathway [6].
That is why the fourth entry exists. Because the pathways are independent, activating both is not redundant: co-activation of the two cloned receptors in transfected cells produced roughly double the cAMP response of GHRH-receptor activation alone [20]. Combining two GHRH analogues would not do that. Combining a GHRH analogue with a ghrelin-receptor agonist should.
The pulsatility consequence is where the four genuinely separate. Sermorelin adds a brief instruction and gets out of the way, leaving somatostatin and IGF-1 feedback to shape the result [15]. Ipamorelin adds one short, selective spike through a different door [4]. CJC-1295 does something structurally different from either — it holds the GHRH signal on for days, and the measured result was a raised baseline with the pulse pattern intact underneath [12], not the flattened plateau that continuous stimulation might have been expected to produce. The combination is the attempt to have both the floor and the spike, and its unresolved problem is that its two halves operate on timescales that differ by two orders of magnitude [11][4].
How they differ in evidence maturity
This is the comparison that gets omitted most often, and it inverts the usual ranking.
Sermorelin has the strongest human outcome. Height velocity in growth-hormone-deficient children rose from about 4.1 cm/year to roughly 7–8 cm/year on once-daily subcutaneous dosing, without excessive IGF-1 generation [16]. That is a real clinical endpoint in a controlled setting. It is also in a population that has almost nothing in common with the adults sermorelin is marketed to, and a serious editorial has concluded that secretagogue use for aging is not yet justified by evidence [14].
Ipamorelin has the clearest negative. Its one Phase 2 randomised controlled trial in 114 adults missed its primary endpoint — 25.3 hours to first tolerated meal versus 32.6 hours on placebo, not significant [3]. Its supporting literature is otherwise preclinical [5][1] plus an acute human PK study [4].
CJC-1295 has the most interesting measurements and no outcomes. Everything human about it is a hormone level, a half-life or a serum protein [11][12][10]. Those measurements are good ones, and the pulsatility finding is genuinely important [12]. They are still surrogates.
The combination has borrowed everything. Its best supporting data is a meta-analysis of five randomised controlled trials of a different GHRH analogue, tesamorelin, which found reductions in visceral adipose tissue (−27.71 cm²) and hepatic fat (−4.28%), a lean-mass increase of 1.42 kg and no serious adverse events [17], plus a class-level safety review identifying raised blood glucose as the chief concern and long-term cancer and mortality data as still needed [18]. Neither is a study of the blend.
A useful rule falls out of this. Across all four, the further a claim moves from "hormone level changed" toward "life improved", the thinner the support becomes — and almost every consumer-facing claim about this category lives at the far end of that gradient.
What each is actually studied for
Marketing describes all four as broadly interchangeable anti-aging and body-composition tools. The published literature describes something much narrower, and the mismatch is the single most useful thing to carry away from this page.
Ipamorelin was investigated for postoperative ileus — restoring gut function after bowel surgery [3] — and studied preclinically for chemotherapy-associated weight loss [1] and longitudinal bone growth [5]. Not for aging.
CJC-1295 was developed as a long-acting GHRH analogue and its human studies measured pharmacokinetics and axis activation [11][12][10]. Its discontinued Phase 2 programme targeted HIV-associated visceral obesity. Not aging.
Sermorelin was approved for pediatric growth-hormone deficiency [16] and argued editorially as an option in adult-onset growth-hormone insufficiency [15]. Not general wellness.
The combination has no studied indication at all, and the adjacent evidence that comes closest — tesamorelin for HIV-associated lipodystrophy and hepatic fat [17] — is an approved-drug indication in a defined patient population, not a lifestyle protocol.
Every one of these is a specific deficiency or disease context. None is "healthy adult wants to feel younger", which is where essentially all of the demand sits. That is not an argument that the compounds do nothing. It is an argument that nobody has measured what they do in the people most interested in them.