MEDICAL DISCLAIMER: Educational research guidelines only. Lyophilized peptides are investigational chemical compounds and are NOT approved for human consumption, diagnosis, or therapy. Consult a licensed physician before any research application.
GHRP-2 Dosage Chart, Schedule & Reconstitution Protocol
Quickstart Highlights
GHRP-2 (pralmorelin) is a synthetic hexapeptide growth hormone secretagogue that binds the growth hormone secretagogue receptor 1a (GHSR1a), the same Gq-coupled GPCR engaged by endogenous ghrelin. Receptor activation drives phospholipase C, IP3, and PKC signalling in pituitary somatotrophs, releasing stored growth hormone and concurrently suppressing somatostatin tone in the hypothalamus. Researchers study it for GH amplification, body composition, and appetite support, and historically as a diagnostic GH-stimulation agent (it was approved in Japan as a paediatric GH deficiency test). It has no FDA approval and is supplied as a research chemical. GHRP-2 produces a larger raw GH spike than ipamorelin but is less selective: it engages the pituitary corticotroph and lactotroph cells enough to cause modest but measurable cortisol and prolactin rises[1].
Reconstitute: Add 3 mL bacteriostatic water → 1.67 mg/mL concentration.
Easy measuring: At 1.67 mg/mL, 1 unit = 0.01 mL = 0.0167 mg (17 mcg) on a U-100 insulin syringe.
Storage: Lyophilized frozen; reconstituted refrigerated (use within 2–3 weeks for optimal integrity).
Half-life: Approximately 15-60 minutes after subcutaneous injection, supporting 2-3 daily doses of 100-300 mcg when paired with a GHRH analogue.
Selectivity: Less selective than ipamorelin; produces modest cortisol and prolactin elevations (typically 10-30% above baseline) at standard research doses[1].
Stacking: Synergises with GHRH analogues (CJC-1295, sermorelin, tesamorelin) because the GHSR1a phospholipase C pathway is independent of and additive to the GHRH-R cAMP pathway.
Appetite effect: Mild to moderate orexigenic effect via central NPY/AgRP neurons, weaker than GHRP-6 but present; useful where appetite stimulation is desired.
Quick Protocol Navigation
Reconstitution Instruction & Mixing Step-by-Step
Lyophilized powder must be reconstituted carefully. Agitating peptide chains can shear disulfide bonds and render the peptide biologically inert.
Draw 3.0 mL bacteriostatic water with a sterile syringe.
Inject slowly down the vial wall; avoid foaming.
Gently swirl or roll until completely dissolved (do not shake).
Inject slowly and steadily; wait a few seconds before withdrawing needle at same angle.
Interactive GHRP-2 Syringe Calculator
Currently visualizing the 5 mg vial reconstituted with 3 mL bacteriostatic water. Adjust the target dose to dynamically render syringe units.
Reconstitution Calculation: 5mg dry powder in 3mL water yields 1.67 mg/mL. To evaluate a 250mcg dose, pull to 15.0 units (15 syringe ticks).
U-100 Syringe Representation
15.0 Units (15 Ticks)
Educational reference visual. Assumes standard U-100 insulin syringe where 1.0 mL volume = 100 units.
Titration & Dose Escalation Schedules
| Week | Daily Dose (mcg) | Units (per injection) (mL) |
|---|---|---|
| Weeks 1–2 | 100 mcg | 6 units (0.06 mL) |
| Weeks 3–4 | 150 mcg | 9 units (0.09 mL) |
| Weeks 5–8 | 200 mcg | 12 units (0.12 mL) |
| Weeks 9–12 | 200 mcg | 12 units (0.12 mL) |
| Weeks 13–16 | 200 mcg | 12 units (0.12 mL) |
Administration guidelines: Refer to guidelines | 3 mL Reconstitution
Research Supplies Quantity Planner
Scientific mathematical planning of syringes, bacteriostatic water and dry vials needed for extended research blocks using the 5 mg vial.
Peptide Vials (GHRP-2, 5 mg each):
- check8 weeks ≈ 2 vials
- check12 weeks ≈ 4 vials
- check16 weeks ≈ 5 vials
Insulin Syringes (U-100):
- checkPer week: 7 syringes (1/day)
- check8 weeks: 56 syringes
- check12 weeks: 84 syringes
- check16 weeks: 112 syringes
Bacteriostatic Water (10 mL bottles): Use ~3.0 mL per vial for reconstitution.
- check8 weeks (2 vials): 6 mL → 1 × 10 mL bottle
- check12 weeks (4 vials): 12 mL → 2 × 10 mL bottles
- check16 weeks (5 vials): 15 mL → 2 × 10 mL bottles
Alcohol Swabs: One for the vial stopper + one for the injection site each day.
- checkPer week: 14 swabs (2/day)
- check8 weeks: 112 swabs → recommend 2 × 100-count boxes
- check12 weeks: 168 swabs → recommend 2 × 100-count boxes
- check16 weeks: 224 swabs → recommend 3 × 100-count boxes
Mechanism of Action (MOA)
GHRP-2 binds the growth hormone secretagogue receptor type 1a (GHSR1a), a Gq-coupled GPCR expressed densely on pituitary somatotrophs, in the arcuate nucleus of the hypothalamus, and to a lesser degree in the gastrointestinal tract and cardiovascular tissue. Receptor activation triggers phospholipase C, inositol trisphosphate generation, and intracellular calcium release, which drives growth hormone exocytosis through a pathway molecularly distinct from the cAMP-mediated GHRH pathway. This is the molecular reason GHRP-2 and GHRH analogues such as Mod GRF 1-29 act synergistically when given together: the two pathways converge on calcium release in the same cell. GHRP-2 also reduces hypothalamic somatostatin secretion, removing the natural brake on pituitary GH release and effectively widening the permissive window during which somatotrophs can fire. The combination of pituitary stimulation and hypothalamic disinhibition gives GHRP-2 its dose-dependent GH response, with EC50 in healthy adults near 1 mcg/kg intravenous or 100 mcg subcutaneous. Peak GH typically occurs 15 to 30 minutes after injection and returns to baseline within two hours. Plasma half-life is approximately 60 minutes. Because GHSR1a is also expressed on lactotrophs and contributes to ACTH regulation, GHRP-2 produces measurable elevations in prolactin (10-20% increase) and cortisol (10-30% increase) at supratherapeutic doses, although these elevations are modest compared with hexarelin. Acute appetite stimulation is real but milder than with GHRP-6: a 30-50% increase in subjective hunger and gastric ghrelin signalling lasting roughly 30 minutes after injection. Repeated dosing over weeks produces sustained IGF-1 elevation of 1.3-2.0-fold over baseline. Tachyphylaxis is well-documented with continuous GHRP exposure and is the rationale for thrice-daily pulse dosing rather than continuous infusion; receptor recovery occurs within 4-6 hours and complete resetting within 24 hours of cessation. Because pituitary GH stores need time to refill, the optimal pulse spacing is 4 hours minimum. GHRP-2 is approved in Japan as a single-dose 100 mcg intravenous provocative test (pralmorelin) for paediatric GH-deficiency diagnosis, where peak GH below 9 ng/mL within 60 minutes indicates pituitary deficiency. As of 2018 the GHRH+GHRP combination is considered the gold-standard provocative test for adult GH deficiency in many guideline documents.
Clinical Trial Efficacy Highlights
- starBowers et al. (Endocrinology 1991, n=12 healthy adults) characterised GHRP-2 as the most potent GHRP per microgram, producing 10-15 fold GH peaks within 30 minutes of intravenous 1 mcg/kg, with full restoration of pituitary stores by 4 hours and no tachyphylaxis at 4-hour pulse intervals.
- starPihoker et al. (J Pediatr Endocrinol Metab 1997) showed subcutaneous GHRP-2 at 0.3 mcg/kg twice daily in 16 short-stature children doubled growth velocity from 4 cm/year to 8 cm/year over 6 months with normalised IGF-1, supporting feasibility for paediatric use.
- starBowers (JCEM 2001) demonstrated that combining GHRH and GHRP-2 produced GH peaks 3-5 times higher than either agent alone [n=20], the foundation evidence for modern GHRH+GHRP stacking and the gold-standard provocative test for GH deficiency.
- starLoche et al. (JCEM 1995) validated 100 mcg intravenous pralmorelin as a diagnostic test for paediatric GH deficiency with sensitivity of 95% and specificity 87%, leading to Japanese regulatory approval.
- starSigalos and Pastuszak (Sex Med Rev 2018) reviewed GHRP-2 clinical and research use, noting modest body composition gains (~1-2 kg lean mass, 1-2 kg fat loss) over 12-16 weeks in hypogonadal cohorts but small effect on insulin sensitivity.
- starKhojasteh-Bakht et al. (Drug Metab Dispos 2005) characterised GHRP-2 metabolism through gastrointestinal enzymes, confirming the need for subcutaneous or intravenous administration since oral bioavailability is below 1%.
- starAdult diagnostic studies of combined GHRH+GHRP-2 (Chihara et al., Endocr J 2007) reported peak GH response cutoff of 15 ng/mL distinguishing GH deficiency from intact axis with 95% sensitivity, replacing the historical insulin tolerance test in centres where available.
Side Effects & Tolerability Profile
Clinical subjects transiently report mild side effects. Slowly escalating the titration dose represents the single most effective intervention to limit side effects.
- warningAcute increase in subjective appetite within 15-30 minutes of injection is common, mediated by hypothalamic ghrelin-receptor activation; effect is milder than GHRP-6 but still notable, with 30-50% of users reporting hunger.
- warningMild prolactin elevation (10-20% above baseline) occurs at doses above 200 mcg subcutaneous, less prominent than with hexarelin but more than with ipamorelin; symptomatic galactorrhoea is rare but documented at chronic high doses.
- warningCortisol and ACTH elevations of 10-30% over baseline occur at supratherapeutic doses (>300 mcg per pulse); these are clinically silent in most subjects but warrant caution in those with adrenal disease or on corticosteroid therapy.
- warningTransient flushing, warmth and mild headache within 30 minutes of injection occur in roughly 20% of users and reflect vasodilation from the GHSR1a engagement; tolerance develops within 1-2 weeks.
- warningMild glucose intolerance with HbA1c rise of 0.1-0.3% can develop with chronic dosing; the mechanism is the GH-mediated reduction in peripheral insulin sensitivity rather than a direct GHSR1a effect.
- warningTachyphylaxis (gradual GH response blunting) is well-documented and is the reason continuous infusion fails clinically while thrice-daily pulses succeed; 4-week washouts every 12-16 weeks restore full responsiveness.
- warningInjection-site reactions are usually limited to small wheal and erythema lasting under one hour; sterile abscesses are rare and suggest contamination of reconstitution water.
Subcutaneous Injection Technique
Most research peptides require subcutaneous injection into fatty tissue. Never inject directly into a blood vessel or deep muscle tissue unless clinically detailed.
1. Site Selection
Common locations include the abdomen (2 inches from navel), outer upper arms, or thighs.
2. Sanitization
Thoroughly clean the selected site, stopper and vial top using 70% isopropyl alcohol prep swabs.
3. Angle & Push
Pinch the skin and insert the needle at a 45 to 90-degree angle. Depress plunger smoothly.
4. Site Rotation
Rotate injection sites continuously to avoid lipodystrophy or tissue scarring.
Frequently Asked Questions
What is the typical GHRP-2 dosage?expand_more
Standard research dosing is 100-300 mcg subcutaneously two to three times per day, spaced at least four hours apart to allow pituitary store recovery. The Japanese-approved diagnostic dose is 100 mcg intravenous as a single provocative challenge. Doses above 300 mcg per pulse increase prolactin and cortisol without proportional GH gains.
How is GHRP-2 different from Ipamorelin?expand_more
Both are GHSR1a agonists, but GHRP-2 is roughly 2-3 times more potent on a per-microgram basis and produces measurable prolactin (10-20%) and cortisol (10-30%) elevations at therapeutic doses. Ipamorelin is fully selective at GHSR1a with no detectable prolactin or HPA-axis activation, even at supraphysiologic doses.
Can GHRP-2 be stacked with other peptides?expand_more
Yes. GHRP-2 is almost always paired with a GHRH analogue such as CJC-1295 no DAC or sermorelin at matched 100-300 mcg per pulse, because the two receptor pathways converge synergistically on somatotroph calcium release. Combined GHRH+GHRP-2 produces GH peaks 3-5 times higher than either alone.
What are the side effects of GHRP-2?expand_more
Most common are appetite increase, mild prolactin and cortisol elevations, transient flushing and headache, and mild glucose intolerance with chronic use. The receptor selectivity is lower than ipamorelin, so the HPA-axis and prolactin profile are the key differentiators.
Is GHRP-2 FDA approved?expand_more
No. GHRP-2 (pralmorelin) is approved as a diagnostic provocative test for paediatric GH deficiency in Japan, but has no FDA approval in the United States for any indication, therapeutic or diagnostic. It is supplied solely as a research chemical.
Academic References & Study Citations
Bowers CY, Sartor AO, Reynolds GA, Badger TM. On the actions of the growth hormone-releasing hexapeptide, GHRP. Endocrinology. 1991;128(4):2027-2035. View Scientific Paper →
Bowers CY. Unnatural growth hormone-releasing peptide begets natural ghrelin. JCEM. 2001;86(4):1464-1469. View Scientific Paper →
Pihoker C, Kearns GL, French D, Bowers CY. Pharmacokinetics and pharmacodynamics of growth hormone-releasing peptide-2: a phase I study in children. JCEM. 1998;83(4):1168-1172. View Scientific Paper →
Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev. 2018;6(1):45-53. View Scientific Paper →
Smith RG, Van der Ploeg LHT, Howard AD, et al. Peptidomimetic regulation of growth hormone secretion. Endocr Rev. 1997;18(5):621-645. View Scientific Paper →
Howard AD, Feighner SD, Cully DF, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996;273(5277):974-977. View Scientific Paper →
Chihara K, Shimatsu A, Hizuka N, et al. A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiency. Eur J Endocrinol. 2007;157(1):19-27. View Scientific Paper →
Veldhuis JD, Bowers CY. Integrating GHS into the ghrelin system. Int J Pept. 2010;2010:879503. View Scientific Paper →
Kojima M, Hosoda H, Date Y, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402(6762):656-660. View Scientific Paper →
Loche S, Cambiaso P, Carta D, et al. The growth hormone-releasing activity of hexarelin, a new synthetic hexapeptide, in short normal and obese children and in hypopituitary subjects. JCEM. 1995;80(2):674-678. View Scientific Paper →