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Mod GRF 1-29: quick citable summary
Mod GRF 1-29 is listed by PeptaHub as a muscle & growth peptide with a research only legal-status classification. The page summarizes mechanism, research context, common routes, safety notes, and references for writers and AI answer engines.
PeptaHub. “Mod GRF 1-29: Mechanism, Research Context, Safety.” peptahub.com, 2026. https://peptahub.com/peptides/mod-grf-1-29. Licensed CC BY 4.0.
License: Creative Commons Attribution 4.0 International. Link back to https://peptahub.com/peptides/mod-grf-1-29.
What is Mod GRF 1-29?
Mod GRF 1-29 is a stabilized GHRH analog with four amino acid substitutions that resist enzymatic degradation, intended to produce pulsatile GH release. It is usually paired with a GHRP like ipamorelin. No human trial of Mod GRF 1-29 itself has been published.
Overview
Mod GRF 1-29 (Modified Growth Hormone Releasing Factor 1-29) is a stabilized synthetic analog of endogenous GHRH with four amino acid substitutions that resist enzymatic degradation. Unlike CJC-1295 with DAC, it lacks the Drug Affinity Complex and has a short 30-minute half-life, producing pulsatile GH release that closely mimics natural physiology. It is almost always co-administered with a GHRP such as ipamorelin.
Mechanism of action
Mod GRF 1-29 binds to and activates GHRH receptors on somatotroph cells of the anterior pituitary. The four amino acid substitutions (at positions 2, 8, 15, and 27) protect against dipeptidyl peptidase-IV cleavage and other serum proteases, extending bioactive duration beyond native GHRH (1-29) while maintaining pulsatility. Receptor activation triggers Gs-mediated adenylyl cyclase signaling, elevating intracellular cAMP, which drives GH synthesis and secretion. The resulting GH pulse stimulates hepatic IGF-1 production, skeletal muscle protein synthesis via IGF-1R/PI3K/Akt/mTOR pathways, lipolysis in adipose tissue via hormone-sensitive lipase activation, and collagen synthesis in connective tissue. Peak GH levels occur approximately 30 minutes post-injection, returning to baseline within 2–3 hours, preserving normal GH pulsatility over time.
Reported study ranges
| Purpose | Route | Reported range | Frequency | Notes |
|---|---|---|---|---|
| GH pulse stimulation (combined with GHRP) | subcutaneous | 100–200 mcg | 1–3 times daily | Administer simultaneously with ipamorelin or GHRP-6. Inject on an empty stomach or 2+ hours post-meal for maximal GH pulse. Common protocol: morning fasted + pre-sleep. 12-week on, 4-week off cycles. |
Reported ranges are for research context only. Consult a qualified healthcare professional before using any peptide.
Convert Mod GRF 1-29 research-range units
Need to convert mg to mcg, dose volume, or U-100 syringe units? The Mod GRF 1-29 dose calculator is preloaded with these ranges, or use the general dose unit converter.
Research summary
No published human trial has administered Mod GRF 1-29 itself. The human evidence cited for this peptide comes from studies of the DAC-modified analog CJC-1295 (Teichman et al., JCEM 2006; Ionescu & Frohman, JCEM 2006), which has a fundamentally different pharmacokinetic profile, and from the broader GHRH analog class such as sermorelin. The tetrasubstituted GHRH(1-29) backbone shared by both was shown to resist protease degradation in rats (Jetté et al., Endocrinology 2005). GHRH analogs and ghrelin mimetics such as ipamorelin produce greater-than-additive GH release when combined, an effect established for the drug classes rather than for this specific pairing. No human pharmacokinetic study, dose-response study, or body composition trial of Mod GRF 1-29 has been published as of 2026.[1][2][3][4][5]
Evidence grading
Each claimed benefit is graded by the strength of available evidence. Grades reflect study quality, not effect size.
Strong = multiple RCTs · Moderate = limited trials or observational · Preliminary = animal or in vitro only · Insufficient = anecdotal or no published data
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with Mod GRF 1-29 for synergistic effects.
Legal status
Mod GRF 1-29 cannot legally be compounded in the US today. It is a modified GHRH(1-29) analog closely related to CJC-1295 without DAC, and it is not separately named on the FDA's list of 12 peptides removed from Category 2 on April 15, 2026, nor on either Pharmacy Compounding Advisory Committee agenda. FDA staff have specifically flagged inconsistent naming conventions across peptide bulk substances as a review problem, so the boundary between this substance and CJC-1295 is not cleanly resolved in the public record; this entry does not assume coverage that the FDA has not stated. Most US commercial availability ceased in 2024-2025, and research-use supply chains remain active internationally. Mod GRF 1-29 is not FDA-approved for any indication. Verify current federal and state rules before relying on access claims.
Sourcing & access
Research compound
Mod GRF 1-29 is classified as a research compound. Regulatory status varies by jurisdiction. Always verify current legal status and source from vendors providing third-party certificates of analysis (COA).
Frequently asked questions
Mod GRF 1-29 (also called CJC-1295 without DAC) is a modified growth hormone releasing factor with four amino acid substitutions at positions 2, 8, 15, and 27 that protect against enzymatic degradation. Unlike CJC-1295 with DAC, it has a short 30-minute half-life, preserving natural GH pulsatility.
Mod GRF 1-29 activates GHRH receptors on pituitary somatotroph cells, triggering GH synthesis and secretion via cAMP signaling. The commonly quoted timing — a GH peak around 30 minutes and a return to baseline within 2-3 hours — reflects GHRH class pharmacology rather than a published pharmacokinetic study of this peptide, since none exists.
Side effects include injection site redness or swelling, transient flushing, headache, dizziness, water retention at high doses, and increased hunger when combined with GHRP-6. Mod GRF 1-29 was not among the 12 peptides the FDA removed from Category 2 in April 2026 and cannot legally be compounded in the US.
GHRH analogs and ghrelin mimetics act on different pituitary receptors, and giving both releases more GH than either alone. That synergy is established for the drug classes; no published study measures it for Mod GRF 1-29 with ipamorelin specifically, so figures like "3-10x" that circulate in community sources are not traceable to a trial. Ipamorelin is preferred among GHRPs because it has less effect on cortisol and prolactin.
Research references
- Human growth hormone-releasing factor (hGRF)1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: identification of CJC-1295 as a long-lasting GRF analogPubMed
- Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adultsClinicalTrials.gov
- Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analogPubMed
- Once-daily administration of CJC-1295, a long-acting growth hormone-releasing hormone (GHRH) analog, normalizes growth in the GHRH knockout mousePubMed
- Advances in the detection of growth hormone releasing hormone synthetic analogsReview