Quick summary
Mod GRF 1-29 is a stabilized GHRH analog with four amino acid substitutions that resist enzymatic degradation, producing pulsatile GH release that mimics natural physiology. It is almost always paired with a GHRP like ipamorelin for synergistic 3-10x amplification of GH pulses.
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.
Dosing protocols
| Purpose | Route | Dosage | 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. |
Dosing information is for educational purposes only. Consult a qualified healthcare professional before using any peptide.
Research summary
Preclinical and early clinical research confirms Mod GRF 1-29 potently stimulates pulsatile GH release with a safety profile comparable to sermorelin. Human pharmacokinetic studies show peak GH levels 30–45 minutes post-injection with dose-dependent magnitude. The short half-life confers lower risk of receptor desensitization compared to long-acting GHRH analogs with DAC. Combination studies with ghrelin mimetics (ipamorelin, GHRP-6) demonstrate synergistic 3–10x amplification of GH pulse amplitude versus either agent alone. No large-scale human efficacy trials for body composition have been completed 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
One of 14 peptides under FDA reclassification review (RFK Jr. initiative, 2025–2026). Previously available from US compounding pharmacies as a GHRH analog; most commercial availability ceased 2024–2025. Research-use supply chains remain active internationally.
Sourcing & access
Reclassification in progress
Mod GRF 1-29 is one of 14 peptides under FDA reclassification review. Access may be restored through licensed compounding pharmacies if reclassification is formalized. Check our regulatory timeline for the latest status.
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. Peak GH levels occur approximately 30 minutes post-injection, returning to baseline within 2-3 hours. This preserves normal GH pulsatility and reduces receptor desensitization risk.
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. It is one of 14 peptides under FDA reclassification review.
The GHRH (Mod GRF 1-29) plus GHRP (ipamorelin) combination synergistically amplifies GH pulse amplitude 3-10x versus either agent alone. Ipamorelin is preferred among GHRPs because it minimally affects cortisol and prolactin levels.
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