Ghrelin vs GHRP-6
A neutral, side-by-side comparison of two performance & growth hormone peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
Ghrelin
Endogenous 28-amino acid peptide secreted primarily by the stomach that functions as both the primary hunger signal and a potent growth hormone secretagogue. The n-octanoyl modification at Ser-3 (acylated form) is required for GHS-R1a receptor binding and GH-stimulating activity. Understanding ghrelin explains the mechanism behind the entire GHRP class of research peptides.
Full profileGHRP-6
GHRP-6 is a first-generation synthetic hexapeptide GH secretagogue that strongly stimulates pituitary GH release via ghrelin receptor activation. It is one of the oldest and most well-studied GHRPs, with a large body of research spanning more than three decades. GHRP-6 produces significant GH pulses but is notable for powerfully stimulating appetite — a side effect that can be beneficial for those in a caloric deficit or disadvantageous for those managing body composition.
Full profile| Ghrelin | GHRP-6 | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | GHRL, growth hormone-releasing peptide endogenous, ghrelinergic peptide, acyl ghrelin | Growth Hormone Releasing Peptide-6, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 |
| Evidence | Investigational (in trials) | Preclinical only |
| Dosing range | 0.5mcg/kg–2mcg/kg mcg/kg, IV or SC bolus; endogenous levels peak pre-meal | 100mcg–300mcg mcg, 1–3 times daily, on an empty stomach |
| Administration | Intravenous (research), Subcutaneous injection | Subcutaneous injection, Intramuscular injection |
| Key side effects | Appetite stimulation, Transient hyperglycemia, Water retention, GH pulse stimulation | Strong increase in appetite (most common and notable), Elevated cortisol and prolactin at higher doses, Water retention / bloating, Fatigue at high doses |
| Cited sources | 2 references | 3 references |
Key differences
- Evidence level differs: Ghrelin is investigational (in trials), while GHRP-6 is preclinical only.
- Administration: Ghrelin — Intravenous (research), Subcutaneous injection; GHRP-6 — Subcutaneous injection, Intramuscular injection.
- Dosing units differ: Ghrelin is dosed in mcg/kg, GHRP-6 in mcg — they operate at different scales.
- Frequency: Ghrelin is typically IV or SC bolus; endogenous levels peak pre-meal; GHRP-6 is 1–3 times daily, on an empty stomach.
- Research depth: this profile cites 2 sources for Ghrelin vs 3 for GHRP-6.
How each works
Ghrelin
Ghrelin was discovered in 1999 as the endogenous ligand for the GHS-R1a receptor. Its acylated form activates GH release from the pituitary, stimulates appetite via NPY/AgRP hypothalamic neurons, and modulates energy homeostasis and fat storage. The des-acyl form (majority of circulating ghrelin) lacks GHS-R1a activity but has independent cardiovascular and cellular effects.
GHRP-6
Human studies confirm GHRP-6 robustly elevates GH within 15–30 minutes of injection, with effects diminishing toward baseline within 2–3 hours. Chronic use increases baseline IGF-1. Research also indicates mild stimulation of cortisol and prolactin, particularly at higher doses. Animal models have shown potential cardioprotective, hepatoprotective, and muscle-sparing effects, though human equivalents are not established.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.