Peptide Categories Explained: A Beginner Guide to GHRPs, GLP-1s, BPCs, and More (2026)

# Peptide Categories Explained: A Beginner Guide to GHRPs, GLP-1s, BPCs, and More (2026)

Research peptides span dozens of biological functions — from stimulating growth hormone release to healing gut tissue, modulating immunity, and regulating metabolism. For researchers new to the field, this diversity can be overwhelming. What's the difference between a GHRP and a GHRH analog? Where do GLP-1 agonists fit? Why are BPC-157 and TB-500 in a category together?

This guide breaks down the major peptide categories used in research, explains what each family does at a mechanistic level, introduces the key compounds in each group, and helps you identify which categories align with your research focus.

> Disclaimer: All content on Peptides.SO is for educational and research purposes only. Research peptides are not approved for human consumption or therapeutic use unless otherwise specified by regulatory authorities. Always follow applicable laws and institutional guidelines.

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How Peptides Are Classified

Peptide classification isn't standardized across the literature — different researchers use different organizing principles. The most common approaches include:

• •By function: What does the peptide do in biological systems? (e.g., growth hormone stimulation, tissue repair)
• •By target receptor: Which receptor or receptor family does it bind? (e.g., GLP-1R, GHSR, melanocortin receptors)
• •By origin: Is the peptide endogenous (naturally produced by the body), synthetic, or derived from a natural sequence?
• •By structure: How many amino acids? Is it cyclic or linear? Does it have non-natural amino acids?

For practical research purposes, functional classification is the most useful starting point. That's the framework this guide uses.

The major peptide categories you'll encounter in research are:

1. Growth Hormone Secretagogues (GHS) — GHRPs and GHRH Analogs

2. GLP-1 Receptor Agonists and Metabolic Peptides

3. Healing and Tissue Repair Peptides

4. Immune-Modulating Peptides

5. Cognitive and Neuroprotective Peptides

6. Cosmetic and Skin Biology Peptides

7. Longevity and Bioregulator Peptides

8. Cardiovascular and Cardioprotective Peptides

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Category 1: Growth Hormone Secretagogues (GHS)

Growth hormone secretagogues are peptides that stimulate the secretion of growth hormone (GH) from the anterior pituitary gland. They achieve this through two distinct mechanisms, which define the two major subcategories:

GHRPs (Growth Hormone Releasing Peptides)

GHRPs act on the ghrelin receptor (GHSR-1a) — the same receptor targeted by the hunger hormone ghrelin. Unlike ghrelin, GHRPs are modified to preferentially stimulate GH release with varying degrees of appetite stimulation as a side effect.

Key GHRPs:

Research applications: GHRPs are studied for their roles in body composition (lean mass accretion, fat mobilization), sleep architecture improvement (GH is predominantly secreted during slow-wave sleep), recovery from exercise and injury, and age-related GH decline (somatopause).

GHRH Analogs (Growth Hormone Releasing Hormone Analogs)

GHRH analogs mimic the body's own GHRH — the hypothalamic hormone that signals the pituitary to produce and release GH. They act on the GHRH receptor (GHRHR) rather than the ghrelin receptor.

Key GHRH Analogs:

• •Sermorelin (GRF 1–29): The first 29 amino acids of native GHRH. Short half-life (~10–15 min). The most studied GHRH analog in clinical contexts.
• •CJC-1295 (without DAC): Modified GHRH 1–29 with improved stability. Half-life ~30 minutes. Often combined with GHRPs.
• •CJC-1295 with DAC: Drug Affinity Complex modification extends half-life to ~7–8 days via albumin binding. Creates a sustained GH elevation rather than discrete pulses.
• •Tesamorelin: Full-length GHRH 1–44 analog with trans-3-hexenoic acid modification. FDA-approved for HIV-associated lipodystrophy. The most clinically validated GHRH analog.
• •MOD-GRF 1–29: Another name for CJC-1295 without DAC; commonly used in research.

GHRH + GHRP Synergy: A key research finding is that combining a GHRH analog with a GHRP produces synergistic GH release — far greater than either compound alone. This is because they activate two different receptor pathways that work cooperatively at the pituitary level.

Research applications: Muscle wasting conditions, GH deficiency, metabolic syndrome, lipodystrophy, and age-related declines in GH/IGF-1 axis function.

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Category 2: GLP-1 Receptor Agonists and Metabolic Peptides

Glucagon-Like Peptide-1 (GLP-1) agonists have become among the most clinically significant peptide classes in modern medicine. They represent a major research focus due to their powerful metabolic effects.

How GLP-1 Agonists Work

GLP-1 is an incretin hormone naturally released from intestinal L-cells in response to food. It acts on GLP-1 receptors throughout the body to:

• •Stimulate insulin secretion in a glucose-dependent manner (only when blood glucose is elevated)
• •Suppress glucagon release
• •Slow gastric emptying (increasing satiety)
• •Signal the hypothalamus to reduce food intake
• •Potentially protect beta cells from apoptosis

Key GLP-1 Agonists in Research:

GIP: The "Forgotten Incretin"

Glucose-dependent Insulinotropic Polypeptide (GIP) acts on the GIP receptor (GIPR) and enhances insulin release. Alone, GIP's metabolic effects are modest, but in combination with GLP-1 receptor agonism (as in tirzepatide), the synergy is powerful. Research into GIP receptor biology has expanded dramatically since tirzepatide's approval.

Related Metabolic Peptides

• •AOD-9604: A modified fragment of GH (hGH 176–191) studied for its lipolytic effects without GH-like anabolic or diabetogenic properties
• •HGH Fragment 176–191: The natural C-terminal fragment of GH, with similar research interest in fat metabolism

Research applications: Type 2 diabetes, obesity, non-alcoholic steatohepatitis (NASH), cardiovascular risk reduction, neurodegenerative disease (GLP-1Rs in the brain), and weight management.

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Category 3: Healing and Tissue Repair Peptides

This category encompasses peptides studied for their ability to accelerate healing, reduce inflammation, and support tissue regeneration across multiple body systems.

BPC-157 (Body Protection Compound-157)

BPC-157 is a 15-amino acid synthetic pentadecapeptide derived from a portion of the gastric body protection compound found in human gastric juice. It is the most extensively studied healing peptide in animal model research.

Mechanistic research areas:

• •Angiogenesis promotion via VEGF pathway modulation
• •Nitric oxide system interaction
• •Tendon and ligament fibroblast activity
• •Gut mucosal healing and barrier function
• •Anti-inflammatory effects via suppression of inflammatory mediators
• •Neurological protection and dopamine system modulation

BPC-157 is notable for being studied across an extraordinarily wide range of tissue types — from gut and liver to muscle, tendon, bone, skin, and even cardiac and brain tissue. Most research exists in rodent models.

TB-500 (Thymosin Beta-4 Fragment)

TB-500 is a synthetic analog of Thymosin Beta-4 (Tβ4), a naturally occurring 43-amino acid protein found in virtually all human cells. The most biologically active fragment corresponds to amino acids 17–23 of Tβ4.

Research focus:

• •Actin sequestration and cell motility (Tβ4 is one of the most abundant intracellular proteins, regulating G-actin pools)
• •Wound healing and epithelial migration
• •Stem cell activation and differentiation support
• •Cardioprotection — Tβ4 has received significant research attention for cardiac repair after injury
• •Hair follicle activation

KPV Tripeptide

KPV (Lysine-Proline-Valine) is the C-terminal tripeptide of alpha-MSH (melanocyte-stimulating hormone). It retains anti-inflammatory properties without the pigmentation effects of the full MSH sequence. Research interest includes:

• •Gut inflammation (IBD animal models)
• •Skin inflammation
• •Anti-infective properties

LL-37 (Cathelicidin)

LL-37 is a 37-amino acid human antimicrobial peptide (AMP) — part of the innate immune system. Research applications include:

• •Antimicrobial activity against bacteria, fungi, and viruses
• •Wound healing promotion
• •Immune modulation
• •Biofilm disruption

Research applications (this category): Sports medicine, orthopedic injury recovery, gastrointestinal research, wound healing protocols, and anti-inflammatory studies.

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Category 4: Immune-Modulating Peptides

These peptides interact with the immune system — either enhancing immune function, modulating inflammatory responses, or both.

Thymic Peptides

The thymus gland is the primary site of T-cell maturation and produces several immunomodulatory peptides:

• •Thymosin Alpha-1 (Tα1): A 28-amino acid peptide that activates dendritic cells, NK cells, and T-helper cells. Approved in some countries for hepatitis B, hepatitis C, and as an adjunct in cancer treatment. Extensively researched for immune reconstitution.
• •Thymulin: A 9-amino acid peptide (requires zinc for activity) that promotes T-cell differentiation and has anti-inflammatory properties
• •Thymalin: A thymic extract peptide used in Eastern European bioregulator research for immune senescence

Selank and Semax (Immune-Cognitive Overlap)

While primarily researched for cognitive effects, both Selank (a tuftsin analog) and Semax (an ACTH fragment analog) have immunomodulatory properties. Tuftsin specifically is a natural tetrapeptide that activates macrophages and neutrophils.

Peptide T

Peptide T is an HIV gp120 envelope fragment that blocks HIV entry and has been studied for immune modulation and neurological protection in HIV-positive patients.

Research applications: Autoimmune conditions, immunosenescence, oncology support, infectious disease research, vaccine adjuvant studies.

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Category 5: Cognitive and Neuroprotective Peptides

The blood-brain barrier makes CNS drug delivery challenging, but some peptides cross it efficiently or act via peripheral mechanisms that influence brain function.

Semax

Semax is a synthetic heptapeptide analog of ACTH(4–7) (the 4th through 7th amino acids of adrenocorticotropic hormone): Met-Glu-His-Phe-Pro-Gly-Pro. Originally developed in the Soviet Union, it has been approved in Russia for ischemic stroke and cognitive disorders.

Research interests:

• •BDNF (brain-derived neurotrophic factor) upregulation
• •Neuroprotection against oxidative stress
• •Working memory and attention enhancement
• •Anxiety reduction at certain doses

Selank

Selank is a synthetic analog of tuftsin (Thr-Lys-Pro-Arg) extended with additional amino acids for stability. Like Semax, it was developed in Russia and has regulatory status there.

Research interests:

• •Anxiolytic effects without sedation or dependence
• •Memory consolidation
• •Immune modulation (tuftsin activity)
• •GABAergic system interaction without direct GABA receptor agonism

Dihexa

Dihexa is a hexapeptide analog of angiotensin IV (the C-terminal fragment of angiotensin II). It crosses the blood-brain barrier efficiently and acts on AT4 receptors (now identified as HGF/SF-MET interactions in the hippocampus).

Research interest: Cognitive enhancement, neurogenesis, synaptic plasticity, Alzheimer's disease models (rodent).

Pinealon (EDR Tripeptide)

Pinealon is an Glu-Asp-Arg (EDR) tripeptide — a Khavinson bioregulator peptide with research interest in pineal gland function, melatonin regulation, circadian biology, and neuroprotection.

DSIP (Delta Sleep-Inducing Peptide)

A naturally occurring nonapeptide found in the brain, studied for sleep modulation, stress response, and pituitary regulation.

Research applications: Neurodegenerative disease, cognitive decline, anxiety, sleep disorders, stroke recovery.

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Category 6: Cosmetic and Skin Biology Peptides

Cosmetic peptides represent one of the largest commercial peptide markets. Research in this space focuses on skin aging mechanisms, wound healing, and collagen biology.

Signal Peptides (Matrixyl Family)

Matrixyl (Palmitoyl Pentapeptide-4) contains the sequence Lys-Thr-Thr-Lys-Ser, which signals fibroblasts to produce collagen, elastin, and fibronectin. It is the active component in many anti-wrinkle products.

Matrixyl 3000 combines Pal-GHK with Pal-GQPR (Matrikine peptides).

Neurotransmitter-Inhibiting Peptides

• •Argireline (Acetyl Hexapeptide-3): A hexapeptide analog of the N-terminal portion of SNAP-25, one of the SNARE proteins involved in acetylcholine release at the neuromuscular junction. Studied for localized muscle relaxation as a topical alternative to botulinum toxin approaches.
• •SNAP-8 (Acetyl Octapeptide-3): An extended Argireline sequence with enhanced SNARE interference; studied for deeper wrinkle reduction.

Copper Peptides

GHK-Cu (Glycyl-L-Histidyl-L-Lysine:Copper) is a naturally occurring copper-binding tripeptide found in plasma, saliva, and urine. Extensive research covers:

• •Wound healing and tissue remodeling
• •Collagen and glycosaminoglycan synthesis
• •Antioxidant activity
• •Hair follicle stimulation
• •Anti-inflammatory effects

Melanocortin Peptides

• •Melanotan II (MT-II): A cyclic analog of alpha-MSH (melanocyte-stimulating hormone) that activates melanocortin receptors MC1R, MC3R, MC4R, and MC5R. Studied for skin pigmentation (melanogenesis), sexual function (through MC4R), and appetite suppression.
• •PT-141 (Bremelanotide): A cyclic analog that became the first approved melanocortin receptor agonist — FDA-approved for hypoactive sexual desire disorder in premenopausal women (as Vyleesi).

Research applications: Skin aging, wound healing, pigmentation disorders, sexual medicine.

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Category 7: Longevity and Bioregulator Peptides

This category draws heavily from Russian biogerontology research, particularly the work of Vladimir Khavinson and colleagues at the St. Petersburg Institute of Bioregulation and Gerontology.

Khavinson Bioregulators (Peptide Bioregulators)

The theoretical framework: short regulatory peptides (di-, tri-, and tetrapeptides) derived from tissue extracts act as epigenetic regulators — specifically binding to gene promoter regions and activating expression of proteins relevant to the tissue of origin.

Key bioregulators by tissue target:

Epitalon in Detail

Epitalon (Epithalamin) — Ala-Glu-Asp-Gly — is the most researched longevity bioregulator. Research areas include:

• •Telomere elongation: Animal studies have shown Epitalon can increase telomerase activity and elongate telomeres in somatic cells, which typically shorten with each cell division
• •Melatonin regulation: Stimulates pineal gland melatonin production, particularly in aged subjects
• •Antioxidant activity: Reduces lipid peroxidation and reactive oxygen species
• •Longevity studies: Soviet/Russian animal studies (frogs, rats, mice) consistently showed increased median and maximum lifespan in Epitalon-treated groups
• •Cancer prevention: Some studies suggest inhibitory effects on carcinogenesis via hormonal normalization

Research applications: Anti-aging research, telomere biology, chronobiology, epigenetics of aging.

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Category 8: Cardiovascular and Cardioprotective Peptides

Angiotensin System Peptides

The renin-angiotensin-aldosterone system (RAAS) involves multiple peptide hormones. Research peptides targeting this system include:

• •Angiotensin 1–7: A heptapeptide counterregulatory to angiotensin II, acting on Mas receptors to produce vasodilatory, anti-inflammatory, and cardioprotective effects
• •Alamandine: Similar to Angiotensin 1–7, acting on MrgD receptors

Thymosin Beta-4 (Cardiac Focus)

Thymosin Beta-4 has received significant research attention for its cardioprotective properties — particularly:

• •Reducing cardiomyocyte apoptosis after ischemia-reperfusion injury
• •Promoting cardiac progenitor cell activation
• •Attenuating adverse cardiac remodeling

Natriuretic Peptides

While BNP (B-type natriuretic peptide) and ANP are endogenous and not typically used as research peptides in the same way, their biology underpins research into heart failure, volume regulation, and cardiac biomarkers.

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Which Category Matches Your Research Focus?

Use this quick-reference framework to identify where to start:

If your research involves:

• •GH axis, body composition, recovery → Growth Hormone Secretagogues (GHRPs + GHRH analogs)
• •Metabolic disease, obesity, diabetes → GLP-1 agonists, GIP, metabolic peptides
• •Wound healing, tissue repair, gut health → BPC-157, TB-500, KPV, LL-37
• •Immune function, infection, autoimmunity → Thymosin Alpha-1, Thymulin, LL-37
• •Cognitive function, neuroprotection → Semax, Selank, Dihexa, Pinealon
• •Skin biology, aging markers, topical applications → GHK-Cu, Argireline, Matrixyl, Melanotan II
• •Aging biology, longevity, epigenetics → Epitalon, Khavinson bioregulators
• •Cardiovascular biology → Angiotensin 1–7, Thymosin Beta-4

Crossover Compounds

Some peptides appear across multiple categories. BPC-157, for example, has documented research across gut healing, tendon repair, neurological protection, and cardiovascular function. Similarly, Thymosin Beta-4 intersects immune modulation, wound healing, and cardiac research. This overlap reflects the pleiotropic nature of most peptide signaling pathways.

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Key Terminology Reference

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Next Steps for Beginner Researchers

Understanding peptide categories is the foundation. From here:

1. Select a category that aligns with your research question

2. Review compound-specific guides — each peptide on Peptides.SO has a dedicated profile with mechanism, research data, handling notes, and dosing protocols used in published studies

3. Learn reconstitution and storage — all research peptides require proper reconstitution with bacteriostatic water and correct storage conditions

4. Use the calculator — Peptides.SO's dosing calculator helps you work out research concentrations based on vial size and desired concentration

5. Understand sourcing — quality markers like HPLC certification, mass spectrometry reports, and third-party testing are essential for reliable research outcomes

The Peptide Research Safety Guide covers handling, sterile technique, and contamination prevention — essential reading before beginning any peptide research program.

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Further Reading:

• •What Are Research Peptides? A Beginner Guide to Peptide Science
• •Complete Beginner Guide to Research Peptides: What They Are, How They Work, and Where to Start
• •Essential Peptide Research Equipment Guide: What You Need to Get Started (2026)
• •Research Peptide Terminology Glossary: 50 Terms Every New Researcher Should Know
• •Reconstitution Calculator
• •Peptide Stack Builder

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This article is for educational purposes only. Research peptides are laboratory chemicals for scientific investigation, not approved therapeutic agents unless specifically noted. Follow all applicable regulations and institutional protocols.