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Peptide Terminology A-Z
The peptide space is full of technical terms, abbreviations, and regulatory jargon that can be confusing even for experienced researchers. This glossary defines every term you're likely to encounter across our articles, in supplier documentation, and in clinical discussions.
503A Pharmacy
A compounding pharmacy that prepares patient-specific medications pursuant to a prescription. Regulated by state pharmacy boards. This is the most common pathway for prescribed compounded peptides.
503B Outsourcing Facility
An FDA-registered compounding facility that can produce larger batches under current Good Manufacturing Practice (cGMP) standards. Subject to direct FDA inspection.
AMPK
AMP-activated protein kinase — a cellular energy sensor activated by exercise and metabolic stress. MOTS-C activates AMPK. Key target in metabolic peptide research.
Angiogenesis
Formation of new blood vessels from existing ones. BPC-157's primary healing mechanism. Critical for tissue repair because new blood vessels deliver nutrients and immune cells to injured tissue.
Bacteriostatic Water (BAC Water)
Sterile water containing 0.9% benzyl alcohol as a preservative. Used to reconstitute lyophilized peptides. The benzyl alcohol prevents bacterial growth in multi-use vials.
BDNF
Brain-Derived Neurotrophic Factor — a protein that promotes neuroplasticity, learning, and memory formation. Semax significantly upregulates BDNF expression.
Biofilm
A protective matrix that bacteria create around themselves, shielding them from antibiotics and the immune system. LL-37 disrupts biofilms.
Category 1 (FDA)
Peptides cleared for compounding through 503A and 503B pharmacies. Approximately 14 peptides were reclassified to Category 1 in February 2026.
Category 2 (FDA)
Peptides restricted from compounding due to safety concerns or insufficient data. Under PCAC review. Includes Ipamorelin, Melanotan II, LL-37.
cGMP
Current Good Manufacturing Practice — FDA quality standards for pharmaceutical production. Required for 503B outsourcing facilities.
COA (Certificate of Analysis)
A document from a testing laboratory verifying the identity, purity, and quality of a peptide. Should include HPLC purity, mass spectrometry data, and batch/lot information.
Compounding
The process of creating a customized medication by a licensed pharmacy, typically combining or altering ingredients to meet an individual patient's needs.
GHS-R (Ghrelin Receptor)
Growth Hormone Secretagogue Receptor — the receptor targeted by Ipamorelin and other GH secretagogues to stimulate growth hormone release from the pituitary.
GLP-1 (Glucagon-Like Peptide 1)
An incretin hormone that reduces appetite, slows gastric emptying, and improves insulin sensitivity. Semaglutide and Tirzepatide are GLP-1 receptor agonists.
GHRH
Growth Hormone-Releasing Hormone — the natural hormone that triggers GH release from the pituitary. CJC-1295 and Tesamorelin are GHRH analogs.
HPLC
High-Performance Liquid Chromatography — the gold standard method for determining peptide purity. Separates components to measure the percentage of target compound versus impurities.
IGF-1
Insulin-like Growth Factor 1 — a hormone produced primarily by the liver in response to growth hormone. Used as a blood marker for GH levels. Should be monitored when using GH-releasing peptides.
LAL Test
Limulus Amebocyte Lysate test — detects bacterial endotoxins in injectable preparations. Critical quality check for injectable peptides.
Lyophilized
Freeze-dried. Most research peptides ship as lyophilized powder that must be reconstituted with bacteriostatic water before use.
Mass Spectrometry (MS)
An analytical technique that measures molecular weight, confirming the identity of a peptide. Ensures the product is actually the compound listed on the label.
Melanocortin Receptors (MC1R-MC5R)
A family of receptors involved in pigmentation, appetite, sexual arousal, and inflammation. Targets of Melanotan II, PT-141, and KPV.
NF-κB
Nuclear Factor kappa-B — a key transcription factor controlling inflammatory gene expression. KPV inhibits this pathway. Targeted by many pharmaceutical anti-inflammatory drugs.
PCAC
Pharmacy Compounding Advisory Committee — FDA advisory body that reviews peptides for Category 1 or Category 2 classification.
PCT
Post-Cycle Therapy — protocols to restore natural hormone production after using suppressive compounds. Required after SARMs; generally not needed for peptides.
Reconstitution
The process of dissolving lyophilized (freeze-dried) peptide powder in bacteriostatic water to create an injectable solution.
SASP
Senescence-Associated Secretory Phenotype — the cocktail of inflammatory signals secreted by senescent cells. FOX04-DRI eliminates cells producing SASP.
Secretagogue
A substance that stimulates the secretion of a hormone. CJC-1295 and Ipamorelin are growth hormone secretagogues.
Senescent Cells
Cells that have stopped dividing but resist apoptosis (death). They accumulate with age and drive inflammation. Targeted by senolytic therapies like FOX04-DRI.
Senolytic
A compound that selectively eliminates senescent cells. FOX04-DRI is a peptide senolytic. Dasatinib + Quercetin is a drug/supplement senolytic combo.
Subcutaneous (SC)
Injection into the fatty tissue layer beneath the skin. The most common administration route for peptides. Uses short insulin needles at 45-90° angle.
Telomerase
The enzyme that extends telomeres — the protective caps on chromosomes. Epitalon activates telomerase in somatic cells.
Telomeres
Repetitive DNA sequences at chromosome ends that shorten with each cell division. When critically short, cells enter senescence or die. A biomarker of cellular aging.
Further Reading
- How to Verify Peptide Purity — HPLC, COA, and mass spec explained in depth
- How to Legally Access Peptide Therapy — 503A, 503B, and Category 1/2 explained
- How to Reconstitute & Inject Peptides — Practical BAC water and SC injection guide
- Beginner's Guide to Peptide Protocols — Start here if you're new
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