GHRP-1
Growth hormone-releasing peptide-1, GHRP1, Ala-His-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2
GHRP-1 is a synthetic heptapeptide growth hormone secretagogue from the Bowers and Momany series, developed in the 1980s from enkephalin-derived lead compounds more than a decade before ghrelin itself was identified in 1999. It triggers pituitary growth hormone release by activating the ghrelin receptor GHS-R1a rather than the GHRH receptor. Its only published clinical use is a single growth hormone provocation study in children; it has never been tested as a treatment for anything.
Mechanism
GHRP-1 is an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), a Gq/11-coupled G-protein-coupled receptor expressed on pituitary somatotrophs and on neurons of the hypothalamic arcuate nucleus. Receptor occupancy activates phospholipase C, generating inositol trisphosphate and diacylglycerol, which raises intracellular calcium and triggers exocytosis of stored growth hormone granules. Because GHS-R1a is entirely distinct from the GHRH receptor (a class B, Gs-coupled receptor signalling through cyclic AMP), GHRPs and GHRH act synergistically, releasing more growth hormone together than either alone. Review work by Ghigo and colleagues describes the class as acting by counteracting somatostatinergic activity at both the pituitary and the hypothalamic level, with additional mechanisms not fully defined. That dependence on an intact hypothalamic-pituitary axis is consistent with the only human study, in which most of the eight patients with pituitary insufficiency showed no growth hormone rise at all.
Structurally GHRP-1 descends from the enkephalin-derived leads screened by Momany and Bowers. The pharmacophore shared across the family is the core Ala-Trp-(D-Phe)-Lys motif; Ferro and colleagues mapped modifications at positions 1, 2, 3 and 7 against the framework aa-aa-aa-Ala-Trp-(D-Phe)-Lys using a radioligand competition assay at GHS-R1a. GHRP-1 extends this core with an N-terminal Ala-His pair and places D-2-naphthylalanine at the position occupied by D-Trp in GHRP-6, a bulkier aromatic substitution. Unlike endogenous ghrelin, GHRP-1 carries no serine octanoylation and does not require ghrelin O-acyltransferase to be active. As with all ghrelin-receptor agonists, activation is not confined to the growth hormone axis: variable release of ACTH, cortisol and prolactin accompanies the growth hormone response, and appetite pathways are engaged centrally.
What the research shows
The only published clinical exposure is the 1993 study by Laron, Bowers and colleagues, in which an intravenous bolus was given to fifteen short but otherwise healthy children and adolescents (six prepubertal, nine pubertal) and to eight juvenile patients with pituitary insufficiency. Healthy participants showed a progressive rise in plasma growth hormone peaking at 15 to 30 minutes, significantly greater in pubertal than prepubertal subjects. Most of the hypopituitary patients did not respond. Secondary endocrine effects included a rise in free thyroxine, a fall in thyrotropin and a transient rise in cortisol, while prolactin, luteinising hormone and follicle-stimulating hormone were unchanged. That is essentially the entire clinical dataset: a single-dose provocation test, no control arm, no repeat dosing and no clinical endpoint of any kind.
One further human-adjacent exposure exists. Ferro and colleagues reported receptor-binding activity in samples from excretion studies performed after intranasal administration of GHRP-1, GHRP-2, GHRP-6, hexarelin and ipamorelin, with detection in excreted urine; the published abstract does not state whether those excretion studies were in humans or animals, so this should not be counted as characterised human pharmacology. Everything else in the GHRP-1 literature is the original structure-activity work of Momany and Bowers on rat pituitary cells, later in vitro somatotroph studies, or anti-doping analytical chemistry developing assays for GHRP-1 and its metabolites. There are no controlled trials of body composition, muscle strength, bone density, glucose handling, sleep, wound healing or lifespan in any species, and no repeat-dose toxicology in the public domain. The most relevant context is that growth hormone secretagogues in this class that were developed properly and taken into large trials repeatedly failed to translate raised growth hormone and IGF-1 into durable functional benefit in older adults, with signals of impaired glucose tolerance. GHRP-1 itself was never taken that far.
Evidence assessment
Limited evidence
A single small, uncontrolled clinical study measuring a two-hour hormone response, with no clinical outcome and no replication. Everything else is in vitro, animal or analytical. This is isolated, low-quality human data - the definition of the limited tier - and it is not evidence of benefit for any purpose. Note that the draft's claim of 'six of eight' non-responders among the hypopituitary patients could not be confirmed from the published abstract and has been softened to 'most'.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Growth hormone-releasing activity of growth hormone-releasing peptide-1 (a synthetic heptapeptide) in children and adolescents Preclinical only
Growth hormone rose progressively and peaked at 15-30 minutes, with a significantly greater response in pubertal than prepubertal subjects; most of the hypopituitary patients did not respond. Free thyroxine rose, thyrotropin fell and cortisol rose transiently, while prolactin, luteinising hormone and follicle-stimulating hormone were unchanged.
Design, synthesis, and biological activity of peptides which release growth hormone in vitro Preclinical only
Iterative design from weakly active enkephalin-derived leads produced Tyr-D-Trp-Ala-Trp-D-Phe-NH2, which released growth hormone in vitro at 10-30 ng/ml of medium and was approximately 1000-fold more active than the starting compounds. The authors compared active and inactive analogues and proposed a receptor-binding model.
Conformational energy studies and in vitro and in vivo activity data on growth hormone-releasing peptides Preclinical only
Reported the pentapeptide His-D-Trp-Ala-Trp-D-Phe-NH2 and the hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (the compound later designated GHRP-6) as active in vitro at low concentrations and effective at releasing growth hormone in vivo at modest doses, and related peptide conformation to biological potency.
Structure-activity relationship for peptidic growth hormone secretagogues Preclinical only
Several GHRPs and truncated analogues sharing the core Ala-Trp-(D-Phe)-Lys were assayed at GHS-R1a, and modifications at positions 1, 2, 3 and 7 of the framework aa-aa-aa-Ala-Trp-(D-Phe)-Lys were shown to influence activity. Receptor-binding activity, representing intact GHRPs plus active metabolites, was confirmed in urine from excretion studies after intranasal GHRP-1, GHRP-2, GHRP-6, hexarelin and ipamorelin.
Growth hormone-releasing peptides Preclinical only
GHRPs act through receptors distinct from the GHRH receptor and counteract somatostatinergic activity at both pituitary and hypothalamic level. They are active by intravenous, subcutaneous, intranasal and oral routes, with age-dependent potency that is greater in younger subjects, and mixed effects across growth hormone deficiency and excess states.
Safety
Human safety data amount to one single-dose provocation study in children with no adverse events reported over a few hours; that is not a safety dataset. The same study recorded a transient cortisol rise, a fall in thyrotropin and a rise in free thyroxine. Predictable risks come from the pharmacology rather than the molecule: sustained stimulation of growth hormone and IGF-1 causes fluid retention, peripheral oedema, arthralgia, carpal tunnel symptoms and insulin resistance with impaired glucose tolerance, all documented for growth hormone secretagogues that reached larger trials. Because GHS-R1a activation also drives appetite and ACTH release, increased hunger and cortisol elevation are expected class effects. Anyone with active malignancy, proliferative diabetic retinopathy or untreated pituitary disease sits squarely in the population where growth hormone axis stimulation is contraindicated. Separately, material sold online under this name is unregulated: identity, purity, endotoxin content and sterility are unverified, and mislabelling between the numbered GHRPs is common.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | No UK marketing authorisation. Supply or sale for human use would fall within the definition of an unlicensed medicinal product under the Human Medicines Regulations 2012. |
| United States | Not approved by the FDA for any indication. It is an unapproved new drug and not a lawful dietary supplement ingredient; it is distributed only as a research chemical labelled not for human consumption. |
| WADA (sport) | Prohibited at all times, in and out of competition. Growth hormone-releasing peptides sit under section S2.2.3 of the WADA Prohibited List (growth hormone, its fragments and releasing factors), where GHRP-1 is named among the listed examples. Note: the draft cited section S2.1, which is the erythropoietin section and is incorrect. |
Questions
No. All three act at the ghrelin receptor and share the same aromatic core, but they are different molecules. GHRP-1 is a heptapeptide with an N-terminal Ala-His extension and D-2-naphthylalanine in the third position; GHRP-2 (pralmorelin) is a hexapeptide; GHRP-6 is the hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 reported by Momany and Bowers in 1984. GHRP-2 and GHRP-6 have far more published human data than GHRP-1 does.
No. The single published clinical study used it as a short growth hormone provocation test in children. There has never been a trial of GHRP-1 for body composition, ageing, recovery, sleep or any clinical condition, in any population, of any duration.
The evidence does not support that. Growth hormone secretagogues that were developed properly and taken into large trials in older adults raised growth hormone and IGF-1 reliably but repeatedly failed to produce durable functional benefit, and several signalled worsened glucose tolerance. Higher IGF-1 in later life is, if anything, associated with worse rather than better longevity outcomes in observational work.
Yes, at all times, in and out of competition. Growth hormone-releasing peptides including GHRP-1 are named under section S2.2.3 of the WADA Prohibited List, and anti-doping laboratories have validated urine assays covering GHRP-1 and related compounds.