What are the most-studied peptides for muscle growth?

In the research literature the muscle-growth conversation clusters into three groups: direct anabolic-signalling compounds (IGF-1 LR3, MGF and PEG-MGF), growth-hormone secretagogues that raise the body's own GH/IGF-1 axis (hexarelin, ipamorelin, CJC-1295, GHRP-2, GHRP-6, sermorelin, tesamorelin), and recovery peptides that support the training load rather than build tissue directly (BPC-157, TB-500). Each has a documented mechanism but a large gap between animal-model data and controlled human hypertrophy outcomes.

Do muscle-growth peptides actually build muscle in humans?

The honest answer is that mechanism is not the same as proven outcome. Compounds like IGF-1 LR3 and the GH secretagogues have clear anabolic-signalling pathways in cell and animal models, but rigorous, long-term human hypertrophy trials are largely absent for the research-compound versions. Most human GH-axis data comes from clinical deficiency populations, not healthy trained subjects. They are studied for the pathways, not sold as proven muscle builders - and they are research-use-only, not for human use.

Is MK-677 (ibutamoren) a good muscle-growth peptide?

MK-677 is an orally active GH secretagogue that appears often in muscle-growth discussion, but New-U does not stock it, so it is outside this catalog. Note also that MK-677 is a non-peptide small molecule, not a peptide, despite being grouped with GH secretagogues.

Are muscle-growth peptides banned in sport?

Yes - essentially all of them. IGF-1 and its analogues, GH secretagogues (GHRPs and GHRH analogues) and growth factors like MGF fall under WADA S2 (peptide hormones, growth factors and mimetics) and are prohibited at all times. BPC-157 and TB-500 are also WADA-prohibited. Any tested athlete should treat this entire category as off-limits.

How-to guides

Best Peptides for Muscle Growth Research (2026): The Compounds Labs Actually Study

Quick answer: the peptides that dominate muscle-growth research fall into three buckets - direct anabolic signallers (IGF-1 LR3, MGF/PEG-MGF), GH-axis secretagogues that raise the body's own GH/IGF-1 (hexarelin, ipamorelin, CJC-1295, GHRP-2/6, sermorelin, tesamorelin), and the recovery pair (BPC-157 + TB-500). Every one has a documented mechanism - and a real gap between animal data and proven human hypertrophy. All are research-use-only, not for human use, and WADA-prohibited.

How to read this list. "Best" here means most-studied and most-discussed in muscle-growth research - not a recommendation, a dose, or a promise of results. We describe what each compound does mechanistically and where the evidence stops. There are no protocols on this page.

Group 1: Direct Anabolic Signallers

These act on the muscle-growth pathway directly, rather than by nudging the GH axis upstream.

1. IGF-1 LR3

IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is the compound the muscle-growth literature returns to most. IGF-1 is the downstream mediator of many of growth hormone's anabolic effects; the LR3 modification lowers its binding to IGF-binding proteins and extends the active half-life dramatically versus native IGF-1. In cell and animal models it drives satellite-cell activation, myoblast proliferation and protein synthesis - the core hypertrophy signals. The caveat is large: controlled human muscle-growth trials of LR3 are essentially absent, and IGF-1 signalling is also a cell-proliferation pathway, which is why it is studied carefully. See our IGF-1 DES vs LR3 comparison for the analogue detail.

2. MGF & PEG-MGF

MGF (Mechano Growth Factor) is a splice variant of IGF-1 produced locally in muscle after mechanical overload - the body's own "you just trained, start repairing" signal. It is studied for satellite-cell activation and local repair at the site of damage. Native MGF is extremely short-lived, so PEG-MGF - a PEGylated, longer-acting version - is the form most research uses. Like IGF-1 LR3, the mechanism is well described in models and the human hypertrophy evidence is thin.

Group 2: Growth-Hormone Secretagogues (the GH Axis)

Instead of supplying the anabolic signal directly, these raise the body's own GH and IGF-1 . They split into two mechanistic arms that are usually studied together - the ghrelin arm (GHRPs) and the GHRH arm (GHRH analogues). Our hexarelin vs CJC-1295 piece unpacks that split in detail.

3. Hexarelin

Hexarelin is one of the more potent GHRP-class ghrelin-receptor agonists, and it uniquely engages the CD36 receptor studied in cardiac models. Powerful acute GH release, but with faster desensitisation and less selectivity than the "clean" options below.

4. Ipamorelin

Ipamorelin is the selective GHRP - it triggers a clean GH pulse via the ghrelin receptor with minimal cortisol or prolactin spill-over, which is why it is the most commonly co-studied GHRP. Compare it directly in hexarelin vs ipamorelin.

5. CJC-1295 (no-DAC & DAC)

CJC-1295 is a GHRH analogue acting upstream on the pituitary. No-DAC gives a short, pulse-like signal; the DAC variant binds albumin for a multi-day sustained elevation. It is the canonical GHRH partner to a GHRP - see the CJC-1295 & ipamorelin research guide.

6. GHRP-2 & GHRP-6

GHRP-2 and GHRP-6 are the original growth-hormone-releasing peptides. Both are strong GH releasers; GHRP-6 is notable for a pronounced ghrelin-driven appetite effect, while GHRP-2 is a cleaner, stronger releaser. Both raise cortisol/prolactin more than ipamorelin.

7. Sermorelin & Tesamorelin

Sermorelin is the short GHRH(1-29) fragment; tesamorelin is a stabilised, more potent GHRH analogue with dedicated visceral-fat research and FDA approval in that narrow indication. Both act on the GHRH arm; see tesamorelin vs sermorelin.

Group 3: The Recovery Pair (Support, Not Build)

These do not build muscle - they support the training load so tissue can adapt. They belong on any honest muscle-growth research map because recovery is the rate-limiter for hypertrophy.

8. BPC-157

BPC-157 is the "body protective compound" pentadecapeptide studied for angiogenesis, fibroblast migration and soft-tissue repair in pre-clinical models. It is the recovery half of the well-known "Wolverine stack".

9. TB-500

TB-500 (a thymosin beta-4 fragment) is studied for cell migration, blood-flow and inflammation resolution - the recovery complement to BPC-157.

The At-a-Glance Table

Compound Group Research mechanism WADA IGF-1 LR3 Direct signaller Long-acting IGF-1; satellite-cell & protein-synthesis signalling Prohibited (S2) MGF / PEG-MGF Direct signaller Local IGF-1 splice variant; overload-triggered repair Prohibited (S2) Hexarelin GH secretagogue (ghrelin) Potent GHS-R1a agonist; CD36 cardiac angle Prohibited (S2) Ipamorelin GH secretagogue (ghrelin) Selective, clean GH pulse Prohibited (S2) CJC-1295 GH secretagogue (GHRH) GHRH analogue; no-DAC pulse vs DAC sustained Prohibited (S2) GHRP-2 / GHRP-6 GH secretagogue (ghrelin) Original GHRPs; strong release, appetite (GHRP-6) Prohibited (S2) Tesamorelin / Sermorelin GH secretagogue (GHRH) GHRH analogues; visceral-fat data (tesamorelin) Prohibited (S2) BPC-157 + TB-500 Recovery Soft-tissue repair, angiogenesis, inflammation resolution Prohibited (S2)

Mechanism is not outcome. Every compound here has a real signalling pathway - but rigorous long-term human hypertrophy trials for the research-compound versions are largely missing, and much GH-axis data comes from clinical deficiency populations, not healthy trained subjects. These are research-use-only reagents supplied by New-U for laboratory work, not for human use , and nothing here is dosing guidance or medical advice. Essentially the entire category is WADA-prohibited (S2) - off-limits for any tested athlete. Note also that MK-677 (ibutamoren) is often listed for muscle growth but is not stocked by New-U and is a non-peptide small molecule, not a peptide.

Frequently Asked Questions

What is the single best peptide for muscle growth? There is no honest single answer - the research groups these by mechanism, not by ranking. IGF-1 LR3 is the most-studied direct anabolic signaller; the GH secretagogues work indirectly through the GH/IGF-1 axis; BPC-157 and TB-500 support recovery. "Best" depends entirely on the research question, and none is a proven human muscle-builder.

Why are GH secretagogues studied in pairs? Because the ghrelin arm (GHRPs like ipamorelin) and the GHRH arm (CJC-1295, sermorelin, tesamorelin) act on different receptors and their GH-release effects are additive - a GHRH + GHRP combination is the most-studied secretagogue pairing.

Do I need bacteriostatic water for these? Yes - they ship as lyophilised powder and are reconstituted with bacteriostatic water for laboratory handling. See our bacteriostatic water guide and reconstitution guide.

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Best Peptides for Muscle Growth Research (2026): The Compounds Labs Actually Study

Group 1: Direct Anabolic Signallers

1. IGF-1 LR3

2. MGF & PEG-MGF

Group 2: Growth-Hormone Secretagogues (the GH Axis)

3. Hexarelin

4. Ipamorelin

5. CJC-1295 (no-DAC & DAC)

6. GHRP-2 & GHRP-6

7. Sermorelin & Tesamorelin

Group 3: The Recovery Pair (Support, Not Build)

8. BPC-157

9. TB-500

The At-a-Glance Table

Frequently Asked Questions

Related Reading

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The GH-Axis & Recovery Catalog, Lab-Verified.

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