GHRP-6
Hexapeptide ghrelin-receptor agonist from the GHRP series; a long-standing research tool for growth hormone and appetite signaling.
Overview
GHRP-6 is a synthetic hexapeptide from the growth hormone-releasing peptide series first described in the 1980s by the laboratory of Cyril Bowers. It is an agonist at the ghrelin receptor (GHS-R1a) and has been used for decades as a research tool to study growth hormone secretion and appetite pathways. It belongs to the same peptide family as GHRP-2, ipamorelin, and hexarelin, each with somewhat different potency and side-effect profiles.
Mechanism
Binding to the growth hormone secretagogue receptor 1a activates phospholipase C and intracellular calcium signaling in pituitary somatotrophs, stimulating GH release. The receptor is also expressed in hypothalamic appetite centers, which explains the pronounced hunger response seen with this peptide relative to some other secretagogues. GHRP-6 is often described as producing the strongest hunger signal among the commonly used GHRP research peptides, a property linked to its high efficacy at the ghrelin receptor, and it remains a standard tool in ghrelin-receptor pharmacology.
Dosing
In research protocols GHRP-6 is typically administered by subcutaneous injection, often several times daily and frequently combined with a GHRH-class peptide for a synergistic GH pulse. Research dosing varies by protocol and species; exact figures should be obtained from the primary literature.
Expected Effects
- strong, transient elevation of circulating growth hormone
- increased appetite, consistent with ghrelin-receptor activation
- elevated IGF-1 with repeated dosing in research settings
- acute increases in prolactin and cortisol in some studies
Side Effects & Tolerability
The most commonly reported effects are increased hunger, transient rises in prolactin and cortisol, and injection-site reactions. Because repeated GH-axis stimulation can affect fluid balance and glucose metabolism, these parameters are relevant considerations in longer research protocols, though controlled long-term data are sparse.
Storage
Lyophilized GHRP-6 should be stored desiccated, protected from light, and kept frozen at -20 deg C or below. Once reconstituted in a sterile solvent, solutions should be kept at 2-8 deg C and used within a short period; avoid repeated freeze-thaw cycles.