The Research-Peptide Directory: Every Peptide, Organized

“Peptides” gets used as if it named a single category of thing. It doesn’t. The word covers everything from insulin and the GLP-1 drugs — among the most-studied medicines on earth — to research chemicals sold online with nothing but animal data and forum anecdotes behind them. This directory is the map: every peptide we cover, grouped by what it’s actually for, each linked to a plain-English breakdown of what the evidence does and doesn’t support.

The single most useful skill in this field is placing any given peptide on the evidence spectrum — approved drug, promising-but-preliminary, or hype — before you engage with the claims. Use this directory to find where each one sits.

If you’re brand new, start with The Beginner’s Guide to Peptides, then come back here to go deep.

Start here: the foundations

How peptides work at all — the concepts that make every entry below readable.

• The Difference Between Peptides and Proteins, Explained
• How Peptides Signal: Receptors, Cascades, and Effects
• Receptor Agonists vs Antagonists: A Plain-Language Primer
• How Peptides Are Absorbed: The Bioavailability Problem
• Oral vs Injectable Peptides: Why the Route Matters
• Peptide Half-Life, Explained: Why Dosing Frequency Varies
• Do Peptides Actually Work?

Judging the evidence — and staying safe

The skeptic’s toolkit: how to read the studies, weigh the risks, and understand the legal and quality landscape.

• How to Read a Peptide Study Without Getting Fooled
• Animal Data vs Human Data: The Peptide Translation Gap
• What Phase a Peptide Is In, and Why It Matters
• The Placebo Problem in Peptide Research
• Why Most Peptide Claims Outrun the Evidence
• Why Peptide Dosing in Studies Rarely Matches Marketing
• Peptide Side Effects: What the Safety Data Actually Shows
• Peptides and Cancer Risk: Untangling a Complicated Question
• Peptide Stacking: Why Combining Compounds Multiplies Unknowns
• Peptide Tolerance and Desensitization, Explained
• Peptide Cycling: What the Protocols Claim vs What Is Known
• The Real Risks of Sourcing Peptides Online
• Research Peptides and Purity: What ‘For Research Use Only’ Means
• Are Peptides Legal? The Regulatory Landscape in 2026
• Compounded Peptides and the FDA’s Shifting Stance
• The Economics of Peptide Research: Why Trials Lag
• Reconstitution and Storage: The Science of Peptide Stability
• Injection Technique and Peptides: What the Research Suggests
• Peptides for Women: What the Sex-Specific Data Shows

Growth-hormone peptides & secretagogues

Compounds that aim to raise growth hormone or IGF-1 indirectly — the busiest and most-hyped corner of the field.

• CJC-1295 and Ipamorelin: How the Combo Is Supposed to Work
• Ipamorelin: A Closer Look at the Growth-Hormone Secretagogue
• Sermorelin vs CJC-1295: Comparing Two GH Secretagogues
• GHRP-6 vs GHRP-2: Comparing the Older Secretagogues
• Hexarelin: The Forgotten Growth-Hormone Peptide
• MK-677 (Ibutamoren): The Oral Secretagogue, Explained
• Growth Hormone Secretagogues: Do They Beat Direct HGH?
• Tesamorelin: The One Peptide With Real FDA Approval
• GLP-1 vs Growth-Hormone Peptides: Different Goals, Different Evidence

For deeper reading, see Growth-Hormone Peptides: A Complete Guide.

Healing, repair & recovery

The “regeneration” peptides — heavily marketed for injuries and gut health, almost entirely on preclinical evidence.

• BPC-157: Separating the Evidence from the Hype
• BPC-157 and Gut Health: A Closer Look at the Claims
• BPC-157 for Tendons: What the Animal Studies Found
• BPC-157 vs TB-500: For Injury Recovery
• TB-500: What the Research Does and Doesn’t Show
• Thymosin Beta-4 and Tissue Repair: Reading the Preclinical Data
• Collagen Peptides: One of the Few With Decent Human Data
• Creatine vs Peptides for Recovery: Where the Evidence Stands

Muscle, fat loss & body composition

Peptides pitched for building muscle or stripping fat — including several cautionary tales.

• Follistatin and Muscle Growth: What the Science Says
• IGF-1 LR3 and PEG-MGF: The Muscle-Building Peptides and Their Risks
• AOD-9604: The Fat-Loss Peptide That Didn’t Pan Out
• Adipotide: A Cautionary Tale in Peptide Development
• Tesofensine: Appetite, Weight, and the Open Questions
• 5-Amino-1MQ: NNMT Inhibition and the Hype Cycle

Longevity & mitochondrial peptides

The peptides that show up in anti-aging conversations — from mitochondrial-derived peptides to the bioregulator claims.

• Epitalon: Sorting the Longevity Claims From the Evidence
• Bioregulator Peptides and Aging: A Skeptical Review
• Peptide Bioregulators: Evidence or Marketing?
• Humanin: A Mitochondrial-Derived Peptide Worth Watching
• MOTS-c: The Mitochondrial Peptide, Explained
• SS-31 (Elamipretide): The Mitochondrial Peptide in Trials

Cognition, mood & sleep

• Semax: Nootropic Peptide or Overstated Hype?
• Selank and Anxiety: A Look at the Limited Human Data
• DSIP (Delta Sleep-Inducing Peptide): Does It Help Sleep?

Skin, tanning & cosmetic peptides

Topical and injected peptides marketed for appearance — where “peptide” appears on a lot of labels.

• GHK-Cu: The Copper Peptide Behind the Skin Claims
• Cosmetic Peptides in Skincare: Matrixyl, Argireline, and What Works Topically
• Peptides for Skin: Topical vs Injected Evidence
• Melanotan II: Why the Tanning Peptide Carries Real Risks
• Melanotan I vs Melanotan II: Comparing the Tanning Peptides

Immune, reproductive & other

• Thymosin Alpha-1: What We Know About the Immune Peptide
• LL-37: The Antimicrobial Peptide Behind the Buzz
• Kisspeptin: The Peptide Reshaping Reproductive Research
• PT-141 (Bremelanotide): The Evidence on Libido and Arousal

Where to go next

New peptides get added to the Learn library regularly — browse the full, always-current peptides category for anything not yet listed here. And before acting on anything in this directory, read Peptide Safety: A Practical Framework. None of this is medical advice; decisions about any of these compounds belong with a qualified clinician.