GHRP-2

What it is

GHRP-2 is a synthetic six amino acid peptide that makes the pituitary release growth hormone. It came out of Cyril Bowers' work in the 1980s and 1990s on small peptides that release GH, the same program that produced GHRP-6. Its generic name is pralmorelin, and it carries the development codes KP-102 and GPA-748.

It is one of the few peptides in this group with a regulatory footprint. In Japan, pralmorelin hydrochloride is sold as an injectable diagnostic agent used to test whether a patient's pituitary can still make growth hormone. It has never been approved as a treatment.

How it works

GHRP-2 binds the growth hormone secretagogue receptor (GHS-R1a) in the pituitary and hypothalamus. When the GHRPs were designed, nobody knew what natural hormone used that receptor. In 1999 Kojima and colleagues found it: ghrelin, a peptide made mainly in the stomach. GHRP-2 is, in effect, a small synthetic ghrelin mimic.

That explains its two main properties:

• A strong, fast GH pulse. In the Japanese diagnostic studies, the GH peak arrived within 60 minutes of an intravenous dose in every subject.
• Effects beyond GH. The ghrelin receptor is involved in appetite and feeding, and GHRPs as a class can raise prolactin and cortisol at higher doses. That is the main reason later compounds such as ipamorelin were developed.

GHRPs also act together with GHRH. Combining a ghrelin mimic with a GHRH analogue such as sermorelin or CJC-1295 gives a larger GH response than either alone, which is the logic behind the CJC-1295 and ipamorelin pairing.

What the research found

Human studies

• As a diagnostic test (Chihara 2007). Researchers in Japan gave a single 100 mcg intravenous dose to 77 healthy adults and 58 adults with confirmed GH deficiency. Healthy subjects produced a large GH peak; patients produced almost none. Results were reproducible on repeat testing and only mildly affected by age and body fat. The authors proposed it as an alternative to the insulin tolerance test, which carries the risk of severe hypoglycaemia.
• In GH-deficient children (Mericq 1998). Six prepubertal children received daily subcutaneous GHRP-2 at three rising doses over eight months. Overnight GH secretion rose in a dose-dependent way and growth velocity improved compared with before and after treatment, but IGF-1 did not change and the effect on GH was short-lived. No side effects were reported. The authors concluded a longer-acting form would be needed for real therapeutic use.

These are small, short studies. There are no long-term trials of GHRP-2 in healthy adults, and none measuring body composition, ageing markers or disease outcomes.

Animal studies

Much of the rest of the literature is in animals. A 2017 review of GHRPs describes studies in cancer-bearing rodents in which GHRP-2 increased food intake and prolonged survival, along with a larger body of cell and organ protection work that mostly used GHRP-6.

Side effects reported in studies

The paediatric study reported no side effects or toxicities over eight months. Class effects to know about from the GHRP literature are hunger, and rises in prolactin and cortisol that become more noticeable as the dose goes up. Any compound that raises GH and IGF-1 carries the same theoretical long-term concerns as growth hormone itself: fluid retention, joint aches, reduced insulin sensitivity, and the unresolved question of IGF-1 and cancer risk.

GHRP-2 vs other GH secretagogues

For a wider comparison with growth hormone itself, see HGH vs peptides.

Status in the Philippines

No GHRP-2 product is registered with FDA Philippines, so it cannot be sold locally as a medicine. It circulates through research-chemical suppliers. For athletes, the status is unambiguous: the WADA Prohibited List names GHRP-2 (pralmorelin) under section S2, banned at all times, and anti-doping labs have published methods to detect it in urine. That applies to any athlete competing under a sport body bound by the World Anti-Doping Code.

Storage

Lyophilised GHRP-2 is a small, fairly stable peptide, but heat is its enemy. Keep unmixed vials in the fridge rather than on a shelf in a Manila summer, and do not rely on room temperature through a brownout. Once reconstituted with bacteriostatic water, keep it at 2 to 8°C. The reconstitution calculator covers the arithmetic of mixing a vial.