Chapter 5
The 12 Main Peptide Categories
Understanding peptide categories is essential for matching compounds to your research goals. Each category serves distinct biological functions and targets specific pathways in the body.
5.1 Signaling Peptides
Peptides that send a message to cells — turning pathways on or off.
Examples: BPC-157, GHK-Cu, AHK-Cu, KPV, LL-37, Thymosin Alpha-1
Primary Roles: Repair, inflammation modulation, immune regulation, angiogenesis
5.2 Growth Hormone Axis Peptides (GHRH + GHRP)
Peptides that stimulate the GH–IGF-1 axis through either the GHRH receptor or ghrelin receptor.
GHRH
CJC-1295, Sermorelin, Mod-GRF
GHRP
Ipamorelin, GHRP-2, GHRP-6, Hexarelin
Primary Roles: GH release, recovery, fat loss, sleep optimization, muscle repair
5.3 Metabolic & Mitochondrial Peptides
Peptides that upgrade energy production, mitochondrial function, or metabolism.
Examples: MOTS-c, SS-31, 5-Amino-1MQ, AOD-9604, Cagrilintide
Primary Roles: Fat loss, insulin sensitivity, ATP efficiency, metabolic flexibility
5.4 Neuropeptides / Cognitive Peptides
Peptides that influence the brain, cognition, focus, memory, or mood.
Examples: Semax, Selank, Cerebrolysin, DSIP, PE-22-28, Pinealon, Dihexa
Primary Roles: Focus, neuroprotection, anxiety modulation, sleep, memory enhancement
5.5 Cosmetic / Regenerative Peptides
Topical or injectable peptides for skin, hair, collagen, elastin, and angiogenesis.
Examples: GHK-Cu, AHK-Cu, Melanotan-1/2, Copper tripeptides, SNAP-8
Primary Roles: Skin regeneration, pigmentation, wrinkle repair, hair follicle activation
5.6 Immune-Modulating Peptides
Peptides that support, regulate, or balance immune pathways.
Examples: Thymosin Alpha-1, TB-500, LL-37, Thymalin, ARA-290
Primary Roles: Inflammation control, immune enhancement, tissue repair, pathogen defense
5.7 Weight-Loss / Appetite-Modulating Peptides
Peptides that affect GLP-1, GIP, amylin, leptin, or energy balance.
Examples: Retatrutide, Tirzepatide, Semaglutide, Tesofensine, Cagrilintide, Mazdutide, Survodutide
Primary Roles: Appetite suppression, metabolic enhancement, fat loss, blood sugar regulation
5.8 Muscle-Building / Recovery Peptides
Peptides that support hypertrophy, muscle repair, and performance.
Examples: IGF-1 LR3, Follistatin-related compounds, BPC-157, TB-500, GHRH/GHRPs
Primary Roles: Muscle growth, tendon/ligament repair, faster recovery
5.9 Sexual Function / Libido Peptides
Peptides that influence arousal pathways, blood flow, or dopamine circuits.
Examples: PT-141 (Bremelanotide), Oxytocin, Kisspeptin-10
Primary Roles: Libido enhancement, arousal, fertility pathway support
5.10 Anti-Inflammatory / Autoimmune Modulating Peptides
Closely tied to immune peptides, but specifically designed to modulate inflammation or autoimmune activity.
Examples: KPV, ARA-290, LL-37, VIP (Vasoactive Intestinal Peptide)
Primary Roles: Gut repair, systemic inflammation reduction, tissue protection, autoimmune modulation
5.11 Sleep & Circadian Peptides
Peptides that support sleep architecture, melatonin pathways, or parasympathetic activation.
Examples: DSIP (Delta Sleep Inducing Peptide), Epitalon, Pinealon
Primary Roles: Deep sleep, recovery, nervous-system down-regulation, circadian rhythm support
5.12 Regenerative Peptide Hybrids / Multi-Pathway Peptides
Newer synthetics designed to hit multiple pathways at once for enhanced effects.
Examples: FOXO4-DRI, P21, KLOW blend, Glow Stack, Cartalax
Primary Roles: Senolytic activity, cellular cleanup, multi-system optimization, longevity support
5.13 FAQ — Peptide categories
How many main peptide families are there?
This guide distinguishes 12 main categories by biological target: signaling, growth-hormone axis, metabolic, neuropeptides, cosmetic, immune-modulating, weight-loss, muscle-building, sexual function, anti-inflammatory, sleep and regenerative hybrids.
Can one peptide belong to several categories?
Yes. Many peptides have pleiotropic effects: a regenerative peptide can also be anti-inflammatory. The category reflects the primary use, not a strict boundary.
Which category is most studied for beginners?
Signaling and recovery peptides (e.g. BPC-157 or TB-500) are often cited as entry points because their profile is well documented in research. Research use only.
Are cosmetic peptides used like the others?
Not always: many are applied topically rather than injected. The route of administration depends on the molecule and its stability.
Scientific references
- Muttenthaler M, King GF, Adams DJ, Alewood PF. Trends in peptide drug discovery. Nature Reviews Drug Discovery. 2021;20(4):309-325. doi:10.1038/s41573-020-00135-8 · PMID 33536635
- Wang L, Wang N, Zhang W, et al. Therapeutic peptides: current applications and future directions. Signal Transduction and Targeted Therapy. 2022;7:48. doi:10.1038/s41392-022-00904-4 · PMID 35165272