GHRP-2
Also known as Pralmorelin, KP-102, Growth hormone releasing peptide 2, GHRP Kaken 100
GHRP-2 is a six amino acid ghrelin receptor agonist that produces a larger growth hormone pulse than ipamorelin but also raises cortisol and prolactin and stimulates appetite. It is licensed in Japan as a diagnostic test for growth hormone deficiency and is used off label in the community as a stronger, less selective alternative to ipamorelin.
Reviewed by the amino101 editorial team. .
Quick start
What people commonly do. Not a prescription.- Typical dose
- 100 to 300 mcg
- How often
- 1 to 3 times daily
- Where
- Subcutaneous, belly or thigh
- Timing
- Empty stomach, most often before bed; no food for 20 to 30 minutes after; extra doses on waking or after training
- Effects timeline
- hunger and flushing within the hour, deeper sleep 1 to 2 weeks, IGF-1 rise by 4 weeks, body composition 2 to 3 months
- Storage
- Lyophilized in freezer or fridge away from light; reconstituted in fridge 2 to 8 C, use within 4 weeks
- Cycle length
- 8 to 12 weeks
- Break between
- a few weeks off, recheck IGF-1, cortisol and prolactin before the next run
A 5 mg vial in 2 mL gives 2.5 mg per mL, so 100 mcg is 4 units and 300 mcg is 12 units on an insulin syringe.
Overview
GHRP-2 is a synthetic hexapeptide from the second generation of growth hormone releasing peptides developed by Cyril Bowers and colleagues in the late 1980s and early 1990s. It acts on the ghrelin receptor in the pituitary and hypothalamus to trigger a pulse of growth hormone. Kaken Pharmaceutical developed it in Japan under the name pralmorelin, and it is approved there as an intravenous diagnostic test for growth hormone deficiency. It has never been approved anywhere as a treatment, and in the rest of the world it is sold as a research chemical.
The human data are better than for most research peptides because of its clinical development. Single dose studies in adults and children show reliable, dose dependent growth hormone release by intravenous, subcutaneous, intranasal and even oral routes. An eight month study of subcutaneous GHRP-2 in short children produced modest growth acceleration. The same studies document its drawbacks: at effective doses it raises ACTH and cortisol, raises prolactin, and increases food intake. A controlled study in healthy men found a measurable increase in meal size after infusion, which is why it is thought of as the middle ground between the clean ipamorelin and the hunger inducing GHRP-6.
In community protocols GHRP-2 is used at 100 to 300 mcg one to three times daily, almost always alongside a GHRH analog such as CJC-1295 without DAC, because the two pathways multiply each other. People choose it over ipamorelin when they want a bigger pulse and do not mind some appetite, and avoid it when cortisol or prolactin are already a concern. This page is educational; it reports what appears in research and community use, not a dosing recommendation.
How it works
GHRP-2 is a full agonist at the growth hormone secretagogue receptor, GHS-R1a, the receptor that ghrelin binds. In the pituitary it raises intracellular calcium in somatotrophs and triggers growth hormone release directly. In the hypothalamus it increases GHRH neuron activity and reduces somatostatin output, so the pulse is larger than pituitary stimulation alone would give, and it is largest of all when a GHRH analog is given at the same time. Unlike ipamorelin, GHRP-2 also activates pathways that drive ACTH and prolactin release, so cortisol and prolactin rise for an hour or two after a dose. The ghrelin receptor also sits on appetite neurons, which explains the hunger. Growth hormone then acts on the liver to raise IGF-1 over days to weeks.
Where the research stands
Growth hormone releaseStrong evidence
- Dose dependent GH pulse. Repeated human studies show reliable growth hormone release by several routes, with a larger pulse than ipamorelin at matched doses.
- Synergy with GHRH analogs. Human data show the GHRP plus GHRH combination releases more than the sum of either alone.
- Diagnostic stimulation testing. Approved in Japan for this purpose, backed by studies in children and adults.
Growth in children with short statureModerate evidence
- Height velocity. An eight month pilot study showed increased growth rate; it was never developed into an approved treatment.
AppetiteModerate evidence
- Increased food intake. A controlled study in healthy men documented a meaningful rise in meal size, which can be a goal or a problem depending on the user.
Body composition and recoveryEmerging
- Fat loss and lean mass. No human outcome trials; expectations rest on growth hormone physiology and on community reports.
- human RCTIntravenous GHRP-2 at 1 mcg per kg produced a growth hormone peak in healthy adults several times larger than GHRH alone, and the combination of the two was greater than the sum of each.
- human pilotEight months of twice daily subcutaneous GHRP-2 in short prepubertal children increased height velocity compared with pretreatment baseline.
- human RCTGHRP-2 infusion increased food intake by roughly a third at a test meal in healthy men compared with saline.
- clinical (approved drug)Intravenous and intranasal GHRP-2 reliably distinguished children with growth hormone deficiency from short normal children, the basis for its Japanese diagnostic approval.
- human RCTAcross acute dosing studies GHRP-2 raised cortisol, ACTH and prolactin alongside growth hormone, in contrast with ipamorelin which does not.
Rodent and in vitro mean no human data for that finding. Human pilot means small, often uncontrolled. Human RCT means randomized and controlled. Clinical means an approved drug with regulatory data.
Levels over time
Modeled from the half-life. Illustrative, not measured.A half-life of 45 min against dosing every 24 h means each dose has cleared before the next. Nothing stacks; you start from zero every time, and the tissue effect is what carries over.
The pulse is sharp and short, which suits once to three times daily dosing and pairs cleanly with a short acting GHRH analog. Cortisol and prolactin rise over the same window and return to baseline within a couple of hours.
GHRP-2 dosage and protocols
Runs of 8 to 12 weeks are typical, slightly shorter than ipamorelin because of the cortisol and prolactin load. There is no loading phase or taper. Some people use GHRP-2 only for the bedtime dose and ipamorelin for daytime doses to limit hunger and cortisol. Bloodwork for IGF-1, prolactin and morning cortisol at the end of a run is sensible.
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Stacked with a GHRH analog | 100 mcg | once daily before bed, with 100 mcg CJC-1295 no DAC | Subcutaneous, same syringe |
| Solo nightly dose | 200 to 300 mcg | once daily before bed | Subcutaneous |
| Three pulse protocol | 100 mcg | 3 times daily, on waking, after training, before bed | Subcutaneous |
| Appetite support while bulking | 150 to 200 mcg | twice daily, 30 minutes before main meals | Subcutaneous |
Fasted dosing is the rule: carbohydrate and fat in the blood suppress the pulse, so a 20 to 30 minute gap before eating is standard. A bedtime dose lines up with the natural nighttime surge. For appetite, a dose 30 minutes before a meal uses the hunger effect deliberately. When stacked with a GHRH analog, both are drawn into one syringe and injected together.
100 mcg is close to the saturating dose for growth hormone release in most adults; 200 to 300 mcg is used when run alone or when a bigger pulse is wanted at the cost of more cortisol and hunger.
Dose calculator
U-100 insulin syringeUnits are a volume on the syringe, not an amount of peptide. Concentration changes every time you change the water volume. The standalone calculator explains the math.
| Vial | Suggested water | Concentration | Low dose draw |
|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 4 units |
| 10 mg | 3 mL | 3.333 mg/mL | 3 units |
How to reconstitute GHRP-2
- 1
Wash your hands and wipe the work surface. Swab both vial stoppers with alcohol and let them dry.
- 2
Pick the water volume with the calculator above and write it on the vial. The concentration means nothing without it.
- 3
Draw the bacteriostatic water into a mixing syringe.
- 4
Insert at an angle and let the water run down the inside wall. Never squirt it straight onto the powder.
- 5
Swirl gently or leave it to dissolve. Do not shake.
- 6
Label with the date and water volume. Store in the fridge at 2 to 8 C and use within about 4 weeks.
- 7
Unmixed vials keep for months in the fridge and longer in the freezer, sealed and out of light.
- Full walkthrough with syringe reading and site rotation: reconstitution guide.
- ✓White, fluffy cake
Lyophilized powder should look like a small white puck or fluffy cake at the bottom of the vial. That is a proper freeze-dry.
- ✓Clear after mixing
Once dissolved the solution should be water-clear with nothing floating in it.
- !Slight clumping
Small clumps that dissolve with gentle swirling are fine. Shipping compacts powder.
- ✕Collapsed or melted
Powder stuck to the sides, glassy, or shrunken means it got hot in transit. Contact the vendor.
- ✕Cloudy or particles
Persistent cloudiness or visible particles after mixing means degraded or contaminated product. Do not use it.
- Week 1 to 2
Hunger 20 to 40 minutes after each dose, some flushing or lightheadedness, deeper sleep and vivid dreams from bedtime doses.
- Week 2 to 6
Early side effects settle, recovery feels quicker, some water retention at higher doses; IGF-1 is measurably higher by week 4.
- Week 6 to 12
Gradual body composition change if diet and training support it; this is also when prolactin or cortisol related complaints show up in the people prone to them.
Interactions and stacking
CJC-1295 (no DAC)synergistic
The standard pairing; GHRH receptor plus ghrelin receptor produces a pulse several times larger than either alone.
Sermorelinsynergistic
Same two pathway synergy with a milder GHRH analog.
Ipamorelincompatible
Both act on the same receptor so they do not add much together; they are alternated rather than combined.
HGHcaution
Exogenous growth hormone suppresses the pituitary, leaving little for a secretagogue to release.
Insulin and diabetes medicationscaution
Growth hormone and cortisol both raise glucose in the hours after a dose; monitor if you take anything that lowers blood sugar.
Corticosteroidscaution
Glucocorticoids blunt the growth hormone response and stack with the cortisol GHRP-2 already releases.
Food and sugary drinks near the doseavoid
Insulin and free fatty acids after a meal cut the pulse substantially.
The standard pairing. The GHRH analog and the ghrelin agonist act on different receptors and the combined pulse is several times larger than either alone.
Same synergy with a milder GHRH analog; GHRP-2 turns a weak sermorelin pulse into a strong one.
Some people alternate the two, using GHRP-2 for a bigger evening pulse and ipamorelin for daytime doses where hunger and cortisol are unwanted.
Safety
- ▲Hunger shortly after a dose
- ▲Flushing, headache or lightheadedness in the first hour
- ▲Water retention and puffy hands at higher doses
- ▲Tingling in the fingers when stacked heavily
- ▲Raised cortisol, which some people feel as restlessness or poorer sleep from daytime doses
- ▲Raised prolactin, which can show as reduced libido or breast tenderness over longer runs
- ▲Raises cortisol and prolactin after each dose, which ipamorelin does not. Over months this can matter for people with anxiety, sleep problems, gynecomastia or libido concerns.
- ▲Increases appetite. Useful for some, a problem for anyone on a fat loss protocol.
- ▲Prohibited in sport by WADA under S2 as a growth hormone releasing peptide.
- ▲Growth hormone pulses raise blood glucose for several hours afterward; people with insulin resistance or diabetes should watch bloodwork.
- ▲Avoid raising growth hormone and IGF-1 with any active or prior hormone sensitive cancer.
- ▲The Japanese approval is for a one time diagnostic injection, which says nothing about the safety of daily use for months.
- ■Breast tenderness or nipple changes, which point to prolactin
- ■Numbness or carpal tunnel symptoms that persist after lowering the dose
- ■Fasting glucose or HbA1c rising on bloodwork
- ■IGF-1 above the reference range for your age
- ■A new lump, growth or any cancer diagnosis
Community poll
Self-reported by visitors. Not clinical evidence.GHRP-2: frequently asked
What is the usual GHRP-2 dosage?
Community protocols report 100 to 300 mcg per injection, one to three times a day, on an empty stomach. Research shows growth hormone release saturates around 100 mcg in most adults, so the higher doses mostly add cortisol, prolactin and hunger rather than more growth hormone. When stacked with a GHRH analog, 100 mcg of each is the common pairing.
GHRP-2 or ipamorelin?
GHRP-2 gives a larger growth hormone pulse but also raises cortisol and prolactin and makes you hungrier. Ipamorelin gives a smaller pulse with none of those effects. People who want maximum release and do not mind eating more pick GHRP-2; people who want clean, long term use pick ipamorelin. Many run GHRP-2 only for the bedtime dose.
Does GHRP-2 make you hungry like GHRP-6?
Less, but yes. A controlled human study found GHRP-2 infusion increased test meal intake by about a third. GHRP-6 is stronger in this respect, and ipamorelin is nearly neutral. Hunger usually hits 20 to 40 minutes after a dose and fades within an hour or two.
Why is it approved in Japan?
Pralmorelin is approved there as a stimulation test for diagnosing growth hormone deficiency. A single intravenous dose is given and growth hormone is measured afterward; a flat response suggests deficiency. That approval covers one diagnostic injection in a clinic and is not an approval for repeated use.
References
- Growth hormone releasing peptide 2 (GHRP-2) given nasally or orally stimulates growth hormone release in healthy men. Journal of Clinical Endocrinology and Metabolism, 1992
- Effects of eight months of treatment with growth hormone releasing peptide 2 in short children. Journal of Clinical Endocrinology and Metabolism, 1998
- Growth hormone releasing peptide 2 (GHRP-2), like ghrelin, increases food intake in healthy men. Journal of Clinical Endocrinology and Metabolism, 2005
- Diagnostic studies with intravenous and intranasal growth hormone releasing peptide 2 in children of short stature. Journal of Clinical Endocrinology and Metabolism, 1997