What Are Peptides? A Beginner's Guide

Both peptides and proteins are made of amino acids linked by peptide bonds. The distinction is primarily about size:

• Peptides: 2-50 amino acids. Small enough to act as targeted signaling molecules
• Proteins: 50+ amino acids. Larger, more complex structures with diverse functions (enzymes, structural components, transport)

This size difference matters because peptides can be synthesized in the lab relatively easily, are stable enough to survive in the body, and are small enough to interact with specific receptors without triggering the immune response that larger proteins might.

Your body naturally produces thousands of peptides that regulate critical functions:

• Insulin (51 amino acids) — regulates blood sugar. One of the most important peptides in human physiology
• Oxytocin (9 amino acids) — involved in social bonding, childbirth, and lactation
• Endorphins — natural pain relievers produced during exercise and stress
• GLP-1 — incretin hormone that regulates appetite and blood sugar
• Growth hormone-releasing hormone (GHRH) — signals the pituitary to release growth hormone
• GHK-Cu — a copper-binding tripeptide involved in wound healing and tissue repair, which declines with age
• BPC (Body Protection Compound) — found in gastric juice, involved in gut protection

Many research and therapeutic peptides are synthetic versions or analogs of these naturally occurring peptides, designed to be more stable, more potent, or longer-lasting than their natural counterparts.

Peptides function primarily as signaling molecules. They bind to specific receptors on cell surfaces, triggering intracellular cascades that produce biological effects. Think of them as keys that fit specific locks on your cells.

Different peptides use different mechanisms:

• Receptor agonists — Bind to and activate a receptor, mimicking the natural ligand. GLP-1 agonists like tirzepatide activate GLP-1 receptors in the brain and pancreas
• Hormone releasers — Stimulate glands to produce and release hormones. Sermorelin stimulates the pituitary to release growth hormone
• Growth factor modulators — Upregulate or downregulate growth factors involved in tissue repair. BPC-157 upregulates VEGF and promotes angiogenesis
• Gene expression regulators — Influence which genes are turned on or off. GHK-Cu modulates expression of approximately 4,000 genes

Because peptides use the body's existing receptor systems, they tend to produce more targeted effects with fewer off-target consequences compared to synthetic drugs that may interact with multiple pathways.

Research peptides can be categorized by their primary mechanism or therapeutic area:

GLP-1 Receptor Agonists

These peptides mimic the incretin hormone GLP-1, reducing appetite and improving blood sugar control. They include FDA-approved medications like semaglutide and tirzepatide, as well as investigational compounds like retatrutide (a triple agonist targeting GLP-1, GIP, and glucagon receptors).

Use case: weight management, metabolic health, type 2 diabetes.

Growth Hormone Secretagogues & GHRH Analogs

Rather than injecting growth hormone directly, these peptides stimulate the body's own GH production. Sermorelin, tesamorelin, ipamorelin, and CJC-1295 fall into this category. They are commonly combined in protocols like the GH Optimization Stack and Muscle Growth Stack.

Use case: muscle growth, body composition, anti-aging research.

Healing & Recovery Peptides

BPC-157, TB-500 (Thymosin Beta-4), and GHK-Cu are studied for their potential to accelerate tissue repair through growth factor modulation, angiogenesis promotion, and anti-inflammatory pathways. See our BPC-157 vs TB-500 comparison for a detailed breakdown of their differences.

Use case: injury recovery, tissue repair, gut healing.

Nootropic Peptides

Semax and Selank are synthetic analogs of naturally occurring brain peptides, researched for cognitive enhancement, neuroprotection, and anxiolytic effects. Both are actually approved medications in Russia.

Use case: Cognitive enhancement, focus, anxiety management.

Cosmetic & Anti-Aging Peptides

Copper peptides (GHK-Cu), Matrixyl, Argireline, and collagen peptides are used in skincare products and researched for anti-aging properties including collagen stimulation and wrinkle reduction.

Use case: Skincare, hair growth, anti-aging.

Anti-Inflammatory & Immune Peptides

KPV (derived from alpha-MSH) and BPC-157 are researched for anti-inflammatory properties, particularly in gut inflammation and autoimmune conditions.

Use case: Gut health, inflammatory conditions, immune modulation.

Peptides and anabolic steroids are fundamentally different:

Feature	Peptides	Anabolic Steroids
Chemical structure	Amino acid chains	Synthetic testosterone derivatives
Mechanism	Signal through body's own receptors	Directly override hormonal levels
DEA scheduling	Not scheduled (most)	Schedule III controlled substances
Hormonal disruption	Minimal — works with feedback loops	Significant — suppresses natural production
Organ toxicity	Low (at research doses)	Liver, kidney, cardiovascular risks
Muscle-building potency	Indirect — supports GH/recovery	Direct — rapid muscle growth

Peptides are not a "legal alternative to steroids." They work through entirely different mechanisms and produce different types of results.

Now that you understand what peptides are, here are the next steps based on your interest:

• Interested in a specific goal? Browse by goal: weight loss, muscle growth, healing, or hair growth
• Want to learn about a specific compound? Start with BPC-157 (most researched healing peptide) or GHK-Cu (most researched cosmetic peptide)
• Comparing two peptides? See our head-to-head comparison guides, including Tirzepatide vs Semaglutide and BPC-157 vs TB-500
• Want to combine peptides? Explore our Healing Stack, Weight Loss Stack, and other peptide stack protocols with dosing schedules and synergy rationale
• Ready to calculate dosages? Use our peptide calculator
• Concerned about safety? Read Are Peptides Safe? and Are Peptides Legal?
• Need practical guidance? See How to Reconstitute Peptides