Ipamorelin
Growth hormone secretagogue (selective agonist of the ghrelin receptor)
A secretagogue is a molecule that triggers the release of a hormone, here growth hormone.
Ipamorelin releases growth hormone without raising ACTH, cortisol or prolactin, even at more than 200 times the effective dose (Raun, European Journal of Endocrinology, 1998).
It activates the pituitary's ghrelin receptor (GHS-R1a) and triggers a single growth hormone pulse: in humans, the peak comes at about 40 minutes and the half-life is 2 hours (Gobburu, 1999).
It is studied for sleep, recovery and body composition: growth hormone drives the liver to make IGF-1, and its largest pulse occurs early in the night.
- Half-life
- About two hours; the GH pulse occurs within the hour following injection.
- Route
- Subcutaneous injection, timed to align with the natural rhythm of the pulses.
Technical sheet
- Family
- Growth hormone secretagogue (selective agonist of the ghrelin receptor)
- Half-life
- About two hours; the GH pulse occurs within the hour following injection.
- Route
- Subcutaneous injection, timed to align with the natural rhythm of the pulses.
- Time to effect
- Sleep and recovery: first or second week. Body composition: several months, alongside training.
- Level of evidence
- Documented in humans
Chemical identity
- Form
- Synthetic peptide, values for the base form
- CAS No.
- 170851-70-4
Salt form: as stated on the lot's certificate of analysis.
Triggering a pulse, not replacing the hormone
Growth hormone (GH) is released in pulses, mostly at night, on two signals: GHRH permits it, ghrelin triggers it through its receptor GHS-R1a.
Ipamorelin binds this receptor and triggers a short pulse, peaking at about 40 minutes, followed by a return to baseline: the body keeps control of the rhythm.
Selectivity: GH without cortisol or prolactin
The first secretagogues (GHRP-6, GHRP-2) also raised cortisol, prolactin, and appetite.
In Novo Nordisk's foundational research, ipamorelin releases a comparable amount of GH, without a significant rise in ACTH, cortisol, or prolactin, even at high doses. That's what made it the reference secretagogue.
Growth hormone and IGF-1
GH makes the liver produce IGF-1, which supports tissue repair, muscle protein synthesis, and collagen; it also mobilizes fat. Deep sleep and GH reinforce each other: that's why sleep is often the first effect reported.
Effects and realistic timelines
Sleep: the largest growth hormone pulse occurs early in the night
One to two weeks
Recovery: GH drives the production of IGF-1, which supports tissue repair
Two to four weeks
Body composition: GH mobilizes fat and supports muscle protein synthesis
Several months
What you may feel
- Brief hunger after injection (a ghrelin effect), especially at the start.
- Flushing, facial redness, or mild headache within the hour that follows.
- Mild water retention or tingling in the hands if stimulation is too strong.
- Reaction at the injection site.
Stop and consult if
- Persistent tingling or new joint pain (signs of excess GH/IGF-1).
- Intense thirst, heavy urination (blood sugar should be checked).
When to abstain
- Active cancer or a recent history of it (GH and IGF-1 stimulate cell growth).
- Uncontrolled diabetes (GH increases insulin resistance).
- Pregnancy or breastfeeding.
- A known pituitary disorder.
- Minors: growth plates are sensitive to GH.
Anti-doping : Prohibited by the World Anti-Doping Agency (growth hormone secretagogues, S2).
The effects to watch for, and how to reduce them
This sheet is educational. It replaces neither a diagnosis nor follow-up: for any medical condition, pregnancy, breastfeeding or current medication, talk to a health professional.
- CJC-1295 (No DAC)GHRH and ghrelin are the two signals behind the same pulse: a complementarity of mechanism, never tested for this pair.
- CJC-1295 + IpamorelinThe combined formula that brings both together in a single pen.
- RetatrutideIpamorelin acts on growth hormone, retatrutide on appetite and blood sugar: two distinct axes, paired for body composition.
- BPC-157BPC-157 is studied for local repair, ipamorelin for a selective growth hormone pulse: a common pairing in recovery.
To avoid
- Exogenous growth hormone: the effects add up and the natural rhythm is lost.
Pharmacology established in humans (GH release, selectivity, tolerability) and a phase 2 trial that confirms the safety profile. The benefits on sleep, recovery, and body composition rest on the GH/IGF-1 mechanism and on user reports.
1998 · Raun et al., European Journal of Endocrinology
Pharmacological studies (pituitary cells and experimental models)
Ipamorelin releases GH with potency comparable to GHRP-6, without increasing ACTH, cortisol, or prolactin: the demonstration of its selectivity.
1999 · Gobburu et al., Pharmaceutical Research
Healthy human volunteers
Characterization of the dose-response relationship and kinetics in humans: rapid, proportional GH release, and good tolerability.
2014 · Beck et al., Neurogastroenterology and Motility
Randomized phase 2 trial in patients following intestinal surgery
Good tolerability confirmed in humans in a phase 2 trial conducted for a different purpose (the return of bowel function after surgery).
What's the difference from injecting growth hormone directly?
Ipamorelin asks your pituitary gland to release its own GH, in pulses, with the body's normal feedback control still in place. Injected growth hormone imposes a constant level, without that control, and with more side effects.
Why two receptors rather than one?
GH release depends on two receptors: the GHRH receptor, which permits it, and the ghrelin receptor, where ipamorelin acts, which triggers it. In humans, in 1990, a GHRH combined with a secretagogue related to ipamorelin released more GH than the sum of the two given separately.
Glossary (5)
- Secretagogue
- A substance that triggers the secretion of a hormone by the gland that produces it.
- Ghrelin
- The hunger hormone produced by the stomach, which also stimulates the release of growth hormone.
- Pituitary gland
- A small gland at the base of the brain that controls most of the body's other hormone glands.
- IGF-1
- A growth factor produced by the liver under the effect of GH; it's the one that acts on muscles and tissues.
- Pulsatile
- Released in brief waves rather than continuously; this is growth hormone's natural rhythm.