GHRP-6 vs Mod GRF 1-29

Ghrelin receptor agonist; stimulates pituitary GH release and increases appetite via hypothalamic ghrelin pathways

GHRP-6 (growth hormone-releasing peptide 6) is a synthetic hexapeptide GH secretagogue that acts as an agonist at the ghrelin receptor (GHS-R1a) in pituitary somatotrophs and the hypothalamus, stimulating GH release through a mechanism that is synergistic with but distinct from endogenous growth hormone-releasing hormone (GHRH). Like other GHRP-class peptides, it engages hypothalamic arcuate nucleus circuits to potentiate GHRH-driven GH pulses and partially suppress somatostatin inhibitory tone; it was among the first GHRP-class compounds characterized pharmacologically and has been used extensively as a research tool for probing the GH secretory axis. Clinical studies have demonstrated dose-dependent GH release following GHRP-6 administration in human subjects, and the GHRP pharmacological class has been characterized across multiple studies documenting pituitary and hypothalamic mechanisms of action. GHRP-6 is not FDA-approved for any indication; it has been studied as a pharmacological tool and provocative GH stimulation agent but has not been evaluated for safety or efficacy in performance enhancement or muscle building outside research protocols. GHRP-6 dosage in research contexts: studies have used subcutaneous and intravenous doses typically in the range of 100–300 mcg per injection. In research protocols, GHRP-6 is often administered 2–3 times daily — before meals, before training, or before sleep — to leverage the body's natural GH pulse windows. GHRP-6 produces a pronounced appetite stimulation effect (a direct ghrelin-mimetic consequence) that is stronger than what is observed with more selective GHRPs such as ipamorelin; this characteristic is relevant to research contexts studying GH secretion alongside energy intake regulation. GHRP-6 vs GHRP-2: both are non-selective GHRPs producing GH alongside cortisol and prolactin co-stimulation, but GHRP-6 is noted for more pronounced ghrelin-like appetite stimulation, while GHRP-2 produces greater GH output per unit dose in some comparative studies. Neither offers the selectivity profile of ipamorelin, which emerged from subsequent GHRP research specifically to reduce off-target hormonal effects. GHRP-6 is administered by subcutaneous injection following reconstitution with bacteriostatic water. Providers offering GHRP-class secretagogues are listed in the PeptideBase directory.

Modified GHRH analog; binds GHRH receptors with improved stability to produce physiological GH pulses when combined with a GHRP

Mod-GRF 1-29 (also designated CJC-1293 without DAC, or tetrasubstituted GHRH[1-29]) is a synthetic analogue of the first 29 amino acids of growth hormone-releasing hormone, modified at four positions including substitution of norleucine at position 27 to improve proteolytic stability and extend the effective half-life of native GHRH 1-29, thereby producing more sustained pituitary GH stimulation per dose. Like endogenous GHRH, it acts through GHRH receptors on pituitary somatotrophs to stimulate cAMP-mediated GH synthesis and secretion, and is administered to mimic the hypothalamic pulse signal that drives GH release and downstream IGF-1 axis activity. Modified GHRH 1-29 analogues sharing the core amino acid substitutions of Mod-GRF 1-29, specifically [Nle27]GHRH(1-29)-NH2, have been administered to humans in controlled studies that documented sustained GH and IGF-1 axis effects with endocrine, metabolic, and immune endpoints characterized in age-advanced subjects. Mod-GRF 1-29 has not received FDA approval; the related compound sermorelin (unmodified GHRH 1-29) was previously FDA-approved for pediatric GH deficiency but was withdrawn by its manufacturer, and Mod-GRF 1-29 is an investigational compound not approved for any clinical indication. Naming note — Mod GRF 1-29 vs CJC-1295: the research compound marketplace uses several overlapping names for this compound. "Mod GRF 1-29" and "CJC-1295 without DAC" refer to the same tetrasubstituted GHRH(1-29) peptide. "CJC-1295 with DAC" (or simply "CJC-1295" in most clinical protocol contexts) is a different compound — it includes a Drug Affinity Complex (DAC) linker that enables albumin binding and produces a dramatically extended half-life (~8 days vs ~30 minutes for Mod GRF 1-29). CJC-1295 with DAC is used as an infrequent injection (weekly or biweekly) while Mod GRF 1-29 / CJC-1295 without DAC is used at each injection session, typically immediately before or alongside a GHRP such as ipamorelin to maximally leverage the GH pulse window. Dosage in research protocols: Mod GRF 1-29 is typically used at 100 mcg per injection alongside ipamorelin or another GHRP, administered 2–3 times daily or immediately before sleep to align with natural GH secretion peaks. Subcutaneous injection after reconstitution with bacteriostatic water is the standard route. Provider availability for Mod GRF 1-29 and CJC-1295 compounds is listed in the PeptideBase directory.