Ipamorelin
Selective growth hormone secretagogue (GHS) - the cleanest pulse booster in the GHRP class.
Human trialsSyntheticInjectableGHS / ghrelin mimetic
Key facts
Common routesSubcutaneous
Half-life~2 hours
Typical range100-300 mcg/dose
Summary
Ipamorelin is a third-generation selective growth hormone secretagogue: it binds the pituitary ghrelin receptor (GHS-R1a) and triggers a pulsatile GH release. Unlike GHRP-2 and GHRP-6, it does that without touching cortisol, prolactin, or ACTH - which is the reason it's widely described as the “cleanest” GHRP.
It doesn't replace exogenous HGH - it amplifies the body's own pulse. In practice it's almost always paired with a GHRH analog (CJC-1295 DAC or Mod GRF 1-29), and that combination is the actual core protocol; Ipamorelin solo makes less sense pharmacologically.
Mechanism notes
GHS-R1a agonism (ghrelin mimicry)
Binds the pituitary ghrelin receptor and triggers pulsatile GH release. Pulsatile, not flat - closer to physiological nighttime GH than synthetic HGH.
GHRH synergy
Boosts somatotroph sensitivity to GHRH. This is the pharmacological reason the Ipamorelin + CJC-1295 (1:1) pairing hits much harder than either alone - the pulse gets bigger and cleaner.
Selectivity
Highly selective for somatotrophs; essentially no activity on ACTH, cortisol, or prolactin, even at very high doses (Raun, 1998). No cortisol jitter, no gyno risk, none of the extreme hunger spike seen with GHRP-6.
Dosing patterns
Evening protocol (anti-aging / sleep)
100-200 mcg subcutaneous before bed, once daily. Mimics the physiological nighttime GH peak and improves deep sleep and subjective recovery without downregulating natural production.
Bodybuilding protocol (multi-pulse + CJC-1295)
200-300 mcg per dose, 2-3x daily (AM fasted, post-workout, pre-bed) - almost always paired with a GHRH analog like CJC-1295 or Mod GRF 1-29 at 1:1 to keep IGF-1 elevated. Keep carbs and insulin away from the injection window.
Evidence snapshot
Evidence splits into two tracks: a Phase II human trial on postoperative ileus (Beck et al., 2014) missed its primary endpoint but generated solid human safety data. Alongside that, preclinical work consistently documents pulsatile GH release, bone growth, and receptor selectivity.
Human data (Beck 2014)
Phase II RCT in 114 patients: GI endpoint missed, but established a complete safety profile under twice-daily dosing.
Preclinical (Raun 1998, Svensson 1999)
Selectivity confirmed (no ACTH/cortisol/prolactin), consistent longitudinal bone growth in adult rats.
Safety considerations
Generally considered the safest GHRP in the community. Acute side effects are minimal (brief “head rush,” mild water retention, injection-site redness). The practically relevant risks are the class risks of any GH/IGF-1 manipulation: reduced insulin sensitivity on longer cycles and a theoretical growth risk in the presence of existing malignancy.
Key cautions
- Insulin blunts GH release - dose on an empty stomach (3+ hours post-meal) and wait 20-30 min before eating
- 5-on / 2-off (or longer-term cycling) is standard to prevent GHS-R receptor downregulation
- Contraindicated with active cancer or malignancy history - elevated IGF-1 is permissive for cell growth