Half-life
Plasma half-life: approximately 15-30 minutes following subcutaneous injection
Evidence
CAnimal replicated
Mechanism
GHS-R1a agonism on pituitary somatotrophs → Gq/11 → PLC → IP3 + DAG → intracellular calcium release → PKC activation → GH vesicle exocytosis. Simultaneously suppresses somatostatin release from hypothalamic neurons, reducing the primary inhibitory brake on GH secretion. Both actions amplify the GH pulse. When co-administered with GHRH or a GHRH analog (CJC-1295), the two pathways converge — GHRH loads the secretory granules via cAMP/PKA, GHRP-2 triggers release via calcium/PKC — producing synergistic GH output 3-5x greater than either alone.
The Cortisol Problem
GHRP-2 is not selective for pituitary somatotrophs. GHS-R1a activation in the hypothalamus triggers corticotropin-releasing hormone (CRH) release, which hits pituitary corticotrophs and elevates ACTH and cortisol. The cortisol response to GHRP-2 in human studies (Arvat et al. 1997) was comparable in magnitude to hCRH itself. Prolactin elevation also documented. For anyone using GHRP-2 for body composition, this cortisol co-secretion works directly against the anabolic goals: cortisol promotes muscle catabolism, visceral fat accumulation, and impairs sleep quality. This is the defining pharmacological trade-off of GHRP-2 and the primary reason the community has migrated toward ipamorelin.
The Appetite Effect
GHS-R1a is the same receptor as the ghrelin receptor — ghrelin's primary role in the body is appetite stimulation and meal initiation. GHRP-2 mimics this. Laferrere et al. (JCEM, 2005): 7 healthy lean men infused with GHRP-2 ate 35.9% more at an ad libitum meal than during saline infusion. The appetite effect is dose-dependent and transient (hours). For cachexia patients, this is a feature. For fat loss phases, it is a significant practical liability — hunger that fights directly against a caloric deficit.
Where GHRP-2 Sits in the GHRP Class
GHRP class ranking by GH potency (descending): Hexarelin > GHRP-2 > GHRP-6 > Ipamorelin. Ranking by cortisol/prolactin co-secretion (descending): Hexarelin > GHRP-2 ≈ GHRP-6 > Ipamorelin (essentially none). Ranking by appetite stimulation (descending): GHRP-6 > GHRP-2 > Ipamorelin (minimal). GHRP-2 vs GHRP-6: similar GH potency (GHRP-2 marginally higher), similar cortisol/prolactin, less appetite stimulation. For most community applications, GHRP-2 is the preferred choice between the two — more GH, less hunger. But ipamorelin has displaced both for users who prioritize a clean hormonal profile.
The GHRP-2 Stimulation Test
Because GHRP-2 reliably and reproducibly stimulates GH release in a dose-dependent, saturable manner, it has been validated in Japan and some European endocrinology centers as a provocative GH stimulation test for GH deficiency diagnosis. A standard dose (1-2 mcg/kg IV) is administered; peak GH response measured at 30-45 minutes. GH deficiency is diagnosed if the peak response falls below threshold. The GHRP-2 stimulation test has been compared to the insulin tolerance test (ITT) — the gold-standard provocative test — and provides comparable diagnostic accuracy with a more favorable safety profile than the hypoglycemia the ITT requires.
FDA Regulatory Status 2026
Not FDA-approved for any indication in the United States. Was placed on the FDA's Category 2 list (restricting 503A compounding pharmacy use) in 2023-2024. Expected to remain on Category 2 even as some other peptides are reclassified in the 2026 HHS reclassification process, specifically due to its cortisol/prolactin elevation and appetite stimulation profile. Available as a research chemical. WADA S2 banned.
WADA Status
S2 — Peptide Hormones, Growth Factors, Related Substances and Mimetics. Banned at all times (in and out of competition). Detection via urine immunoassay and LC-MS/MS. Athletes in tested sports: absolute prohibition.