The most complete guide to research peptides

BPC-157 (Body Protection Compound) is a synthetic pentadecapeptide derived from a protein found in human gastric juice. It is among the most extensively researched peptides in the community with hundreds of animal studies demonstrating broad regenerative effects. Its primary mechanisms include upregulation of VEGF (vascular endothelial growth factor) for angiogenesis, nitric oxide system modulation, and growth hormone receptor expression upregulation in tendon fibroblasts. This makes it effective for tendon, ligament, muscle, bone, and gastrointestinal tissue repair. The oral route is unique — BPC-157 appears to maintain bioactivity when taken orally, making it accessible for gut-specific applications without injection.

Epithalon (Ala-Glu-Asp-Gly) is a synthetic tetrapeptide derived from the natural peptide Epithalamin, produced by the pineal gland. It has the most extensive anti-aging research base of any peptide — with 35+ years of Russian research including human trials. Its primary mechanism is the activation of telomerase, the enzyme responsible for maintaining and extending telomere length. Shortened telomeres are one of the primary hallmarks of aging; telomerase activation reverses this process. Additionally, Epithalon normalizes cortisol and melatonin secretion, regulates the circadian rhythm, and has shown life extension in multiple animal models. One of the most compelling peptides for serious longevity protocols.

The most widely used peptide combination in the research community for injury recovery. BPC-157 and TB-500 work through complementary and non-overlapping mechanisms — BPC-157 drives localized tissue repair at and near the injection site via VEGF and nitric oxide pathways, while TB-500 provides systemic cellular regeneration body-wide via actin upregulation and cell migration. Together they cover both the acute local repair process and the systemic healing cascade. Particularly effective for tendon, ligament, joint, and muscle injuries that have been slow to heal with conventional approaches.

Semaglutide is a GLP-1 receptor agonist developed by Novo Nordisk, approved as Ozempic (diabetes) and Wegovy (obesity). It works by mimicking the natural GLP-1 hormone, suppressing appetite through hypothalamic signaling, slowing gastric emptying, and improving pancreatic beta-cell function. The SELECT cardiovascular outcomes trial demonstrated a 20% reduction in major adverse cardiovascular events in non-diabetic obese patients — expanding its clinical significance well beyond weight loss. The compounded research version is structurally identical to the pharmaceutical product.

Tirzepatide is Eli Lilly's dual GIP/GLP-1 receptor agonist, approved as Mounjaro (T2D) and Zepbound (obesity). The addition of GIP agonism differentiates it from semaglutide — GIP receptors modulate insulin and glucagon secretion and may improve tolerability. SURMOUNT-1 showed 22.5% weight loss at 15mg vs ~15% for semaglutide at equivalent follow-up. Often cited as the current best-in-class before retatrutide reaches market. Strong body composition data showing preservation of lean mass relative to total weight lost.

Sermorelin is a 29-amino acid analog of GHRH, representing the biologically active fragment of the native 44-amino acid hormone. It was previously FDA-approved as Geref for GH deficiency in children before being discontinued for commercial reasons. As the most studied GHRH analog with the longest track record in anti-aging medicine, it remains popular for conservative GH optimization. Key advantage over Tesamorelin: lower cost per dose. Key advantage over direct GH: maintains the pituitary feedback loop, preventing downregulation of endogenous GH production.

Hexarelin is a synthetic hexapeptide GHRP that produces the strongest GH release of any peptide in its class. Unlike other GHRPs it also binds to CD36 receptors in cardiac tissue, showing cardioprotective effects in research models independent of GH. The tradeoff vs cleaner GHRPs like Ipamorelin is elevated cortisol and prolactin. Receptor desensitization also occurs faster with Hexarelin than any other GHRP, requiring shorter cycles and longer breaks.

GHRP-2 is a synthetic hexapeptide that strongly stimulates GH release via the ghrelin receptor (GHS-R1). It produces a stronger GH pulse than Ipamorelin with more cortisol and prolactin release but less than Hexarelin. The appetite stimulation it causes via ghrelin receptor agonism is a notable effect — beneficial for those seeking to increase caloric intake for muscle building, counterproductive for fat loss protocols. Widely used in clinical and research settings for GH stimulation testing.

Kisspeptin-10 is the biologically active C-terminal decapeptide fragment of kisspeptin-54. It acts on KISS1R receptors in the hypothalamus to trigger pulsatile GnRH release. Unlike exogenous testosterone or LH analogs, it stimulates the entire HPG axis naturally from the top — preserving fertility and testicular function. Research in hypogonadal men shows significant LH and testosterone increases with pulsatile administration. Growing interest as a fertility-preserving alternative to TRT for men who want hormone optimization without suppression.

Oxytocin is a 9-amino acid neuropeptide produced in the hypothalamic paraventricular nucleus. Intranasal administration delivers it to the CNS via the olfactory pathway, where it modulates the amygdala's threat response, reducing social anxiety and promoting trust. Research applications include social anxiety disorder, autism spectrum research, PTSD, and sexual dysfunction. Emerging data also suggests an anti-inflammatory role and potential synergy with peptide recovery protocols.

Gonadorelin is synthetic GnRH — the hypothalamic hormone that triggers LH and FSH release from the pituitary. In TRT research, it's used to counteract the HPG axis suppression caused by exogenous testosterone, maintaining testicular stimulation, preventing atrophy, and preserving fertility. After the FDA restricted compounding of hCG in 2020, gonadorelin became the primary research-available alternative for this application. Pulsatile dosing is critical — twice-daily SubQ injections mimic natural GnRH pulse frequency.

Snap-8 (Acetyl Glutamyl Heptapeptide-3) is a topical peptide that targets the SNARE protein complex at the neuromuscular junction, inhibiting acetylcholine release and reducing muscle contraction intensity. Its mechanism mirrors botulinum toxin but is non-toxic and applicable in cosmetic formulations. Research shows reduction in wrinkle depth with consistent topical use. Often combined with GHK-Cu in anti-aging serums for complementary mechanisms — Snap-8 for expression lines, GHK-Cu for collagen synthesis and skin regeneration.

Matrixyl 3000 is a combination of two palmitoylated peptides developed by Sederma: Palmitoyl Tripeptide-1 (Pal-GHK) and Palmitoyl Tetrapeptide-7 (Pal-GQPR). The tripeptide fragment mimics the N-terminal sequence of collagen type I, signaling fibroblasts to upregulate collagen synthesis. The tetrapeptide reduces interleukin-6 production, dampening the chronic low-level inflammation that degrades skin matrix proteins. It's one of the most widely used cosmeceutical peptides with multiple published studies supporting its efficacy for wrinkle reduction and skin firmness improvement.

Melanotan II is a cyclic lactam analog of alpha-melanocyte-stimulating hormone (alpha-MSH). It binds MC1R receptors in melanocytes to increase eumelanin (brown/black pigment) production, and MC4R receptors in the hypothalamus to enhance libido and suppress appetite. PT-141 (bremelanotide) was developed as a derivative of MT-2 specifically for sexual function by removing the tanning activity. MT-2 produces both effects simultaneously. Nausea and spontaneous erections are commonly reported side effects, particularly at higher loading doses.

AHK-Cu (Alanine-Histidine-Lysine copper complex) is a copper tripeptide with targeted research in dermatology and trichology. Unlike GHK-Cu which has broader tissue regeneration applications, AHK-Cu has a more focused research base specifically around hair follicle biology. Studies show it promotes follicular enlargement, stimulates VEGF expression around follicles, and extends the anagen growth phase. S1 Research carries this compound and it's one of their more unique offerings in the cosmetic peptide space.

KPV (Lys-Pro-Val) is the biologically active C-terminal tripeptide fragment of alpha-melanocyte-stimulating hormone. Its key differentiator from most peptides is oral bioactivity — it resists gastric degradation enough to reach intestinal receptors when taken orally, making it practical for gut-specific research without injection. Anti-inflammatory effects occur through inhibition of NF-κB signaling and reduction of pro-inflammatory cytokines. Research models of IBD, ulcerative colitis, and Crohn's disease have shown significant benefit. Commonly combined with BPC-157 for synergistic gut healing.

LL-37 is a 37-amino acid peptide derived from cathelicidin, a protein produced by neutrophils and epithelial cells as part of the innate immune response. It has a unique amphipathic helical structure that allows it to insert into and disrupt bacterial lipid membranes, killing gram-positive and gram-negative bacteria. Beyond direct antimicrobial activity, LL-37 modulates TLR signaling, promotes wound healing, stimulates angiogenesis, and has anti-biofilm properties that make it potentially useful against chronic infections that are resistant to conventional antibiotics.

Larazotide acetate (AT-1001) is an 8-amino acid peptide that specifically targets the tight junction regulation pathway in intestinal epithelial cells. It acts as a zonulin antagonist — blocking the signaling that opens tight junctions and increases intestinal permeability (leaky gut). Phase 2 trials in celiac disease showed statistically significant reductions in intestinal permeability biomarkers compared to placebo. Unlike BPC-157 and KPV which work through repair and anti-inflammatory mechanisms, Larazotide specifically addresses the structural integrity of the intestinal barrier.

Vasoactive Intestinal Peptide is a 28-amino acid neuropeptide found throughout the nervous and immune systems. It acts as a potent vasodilator and anti-inflammatory agent via VPAC1/VPAC2 receptors. Research applications span from pulmonary arterial hypertension (inhaled VIP has been studied in clinical trials) to autoimmune disease modulation and CIRS treatment protocols. Dr. Ritchie Shoemaker has included VIP in CIRS (mold illness) treatment protocols, driving significant community interest among those with chronic inflammatory conditions.

Follistatin 344 is a 344-amino acid isoform of follistatin, a naturally occurring glycoprotein that binds and neutralizes myostatin (GDF-8), activin, and other TGF-β family members that limit muscle growth. By removing the myostatin brake on satellite cell activation and muscle fiber hypertrophy, it enables muscle growth beyond normal genetic limits. Animal model data is dramatic — myostatin knockout mice develop roughly double the normal muscle mass. Human research is primarily in muscular dystrophy and muscle wasting, but community interest is driven by the performance enhancement potential.

5-Amino-1MQ is technically a small molecule rather than a traditional peptide, but is widely categorized and sold alongside research peptides. It inhibits NNMT, an enzyme overexpressed in adipose tissue that consumes SAM (S-adenosylmethionine) and drives fat cell expansion. By inhibiting NNMT, it reduces fat cell size, increases NAD+ and SAM availability for cellular metabolism, and improves metabolic flexibility. Animal model research shows significant fat reduction and metabolic improvement. Often positioned as an "NAD+ pathway" compound complementary to NMN/NR supplementation.

Humanin is a 21-amino acid peptide encoded in the 16S rRNA region of the mitochondrial genome — making it, along with MOTS-c, one of a small class of mitochondria-derived peptides (MDPs). It declines significantly with age and is measurably higher in centenarians compared to age-matched controls. Its cytoprotective effects span multiple organ systems: neuroprotection (particularly against Alzheimer's-related beta-amyloid toxicity), cardiomyocyte protection, insulin sensitization, and reduction of inflammation. Research by the Cohens lab at USC has been particularly instrumental in mapping humanin's biology.