Ipamorelin vs Sermorelin — GHS vs GHRH research
Ipamorelin and sermorelin are both research compounds investigated for stimulating endogenous growth hormone release — but they target different receptors and produce qualitatively different release patterns. Sermorelin is a 29-amino-acid GHRH(1-29) analogue (the same parent fragment as tesamorelin and CJC-1295); it binds the GHRH receptor on pituitary somatotrophs. Ipamorelin is a 5-amino-acid pentapeptide that binds the ghrelin receptor (GHSR-1a, also called the 'GH secretagogue receptor'). The two receptor systems are complementary: GHRH signalling primes the somatotroph for GH release; GHSR signalling triggers immediate release. Combination research protocols often pair them for additive GH-release effects.
Side-by-side
| ipamorelin-5mg | sermorelin-5mg | |
|---|---|---|
| Receptor | Ghrelin (GHSR-1a) | GHRH receptor |
| Length | 5 amino acids | 29 amino acids |
| Mechanism | GH release pulse trigger | GH release amplitude / priming |
| Half-life | ~2 hours | ~10–20 minutes |
| Selectivity | Highly selective (no cortisol/prolactin/aldosterone effect) | GHRH-selective |
| Effect on appetite | Minimal (unlike ghrelin itself) | None |
| Research dosing | ~100–300 mcg SC, 1-3×/day | ~200-500 mcg SC, daily |
What to know
- ·Sermorelin is essentially identical to natural GHRH — same receptor, same downstream effects, same negative-feedback loop preservation.
- ·Ipamorelin was specifically engineered for GHSR selectivity — unlike older GHS compounds (GHRP-2, GHRP-6, hexarelin) it doesn't cross-react meaningfully with cortisol, prolactin, or aldosterone receptors.
- ·Combination ('GHRH + GHS') research protocols are standard — the two pathways produce additive GH release.
- ·Both are research-use only — neither is FDA-approved (ipamorelin development was discontinued by Novo Nordisk in 2007 in late-stage trials).
- ·Both preserve pulsatility — which is the mechanistic appeal vs direct rhGH administration.
Where the literature diverges
Sermorelin literature is older (development through the 1990s) and has shorter clinical-trial coverage than tesamorelin or CJC-1295. Ipamorelin research is concentrated on phase 2 trials in postoperative ileus (where it was investigated as a prokinetic) and animal-model GH-release studies. Neither has the deep clinical-endpoint data of tesamorelin.
FAQ
Why pair them?+
GHRH analogues (sermorelin, tesamorelin, CJC-1295) prime the somatotroph and increase the GH release amplitude when triggered. GHS compounds (ipamorelin, GHRP-2) trigger immediate release. The combination produces both 'larger pulse magnitude' AND 'pulse triggering' — additive in animal-model and human PK studies.
Why is ipamorelin not approved?+
Novo Nordisk advanced ipamorelin through phase 2 trials for postoperative ileus and abandoned development in 2007 for strategic reasons (the indication was deprioritised). The compound never had a focused phase 3 programme for any indication. As of 2026, ipamorelin remains research-grade.
Which raises IGF-1 more?+
Direct comparison studies are limited. In animal-model and small human PK studies, sermorelin alone produces measurable IGF-1 rises with daily dosing; ipamorelin alone does the same to a similar magnitude. Combination dosing produces the largest effect. Tesamorelin (longer half-life and N-terminal modification) produces larger sustained IGF-1 rises than sermorelin in published trials.
This is a research-context comparison of compound mechanism and published trial outcomes. Not medical advice. Both compounds are research-use only when sold by Omega Grade — for in vitro laboratory investigation, not human or veterinary administration.
- ComparisonSermorelin vs CJC-1295 — same parent, different half-life
Sermorelin and CJC-1295 are both modified GHRH(1-29) analogues. The key difference is half-life — minutes vs days — and what that means for research-protocol design.
- ComparisonIpamorelin vs MK-677 — injectable vs oral GH secretagogues
Both target the GHS receptor. Ipamorelin is short-acting and injectable; MK-677 (ibutamoren) is oral with a 24-hour half-life. The literature on the difference is meaningful.