Peptide Glossary — Key Terms Explained
A comprehensive glossary of the most common terms you will encounter in the PepOS app and peptide community.
A
Amino Acid The building blocks of peptides and proteins. There are 20 standard amino acids. Peptides are chains of 2-50 amino acids linked by peptide bonds.
Angiogenesis The formation of new blood vessels from existing ones. BPC-157 promotes angiogenesis, which is why it accelerates healing — new blood vessels bring nutrients and oxygen to injured tissue.
B
BAC Water (Bacteriostatic Water) Sterile water containing 0.9% benzyl alcohol as a preservative. Used to reconstitute lyophilized peptides. The benzyl alcohol prevents bacterial growth, allowing the reconstituted vial to last 28-30 days refrigerated.
Bioavailability The percentage of an administered compound that reaches systemic circulation. Subcutaneous injection has high bioavailability (near 100%). Oral peptides have much lower bioavailability because stomach acid degrades them.
Biomarker A measurable indicator of biological state. Blood markers like IGF-1, fasting glucose, and hs-CRP are biomarkers used to assess peptide protocol effectiveness.
BPC (Body Protection Compound) A pentadecapeptide (15 amino acids) derived from human gastric juice. BPC-157 is the most studied sequence, known for tissue repair and gut healing properties.
C
Certificate of Analysis (COA) A document from an independent lab verifying a peptide's identity, purity, and safety. Look for HPLC purity above 98%, endotoxin testing, and mass spectrometry confirmation.
Cycle A defined period of using a peptide protocol, typically measured in weeks. Example: "an 8-week BPC-157 cycle." Cycling includes both the on-period and the off-period between cycles.
D
Desensitization Reduced response to a compound after prolonged use. Receptors downregulate when continuously stimulated. This is why cycling (taking breaks) is important — it allows receptors to resensitize.
E
Endotoxin Bacterial toxins that can contaminate poorly manufactured peptides. Endotoxin testing on a COA confirms the product is free of these contaminants. Injection of endotoxin-contaminated products causes fever, inflammation, and illness.
G
GH (Growth Hormone) A 191-amino acid protein produced by the pituitary gland. GH promotes growth, cell repair, and metabolism. GH secretagogues (CJC-1295, Ipamorelin, MK-677) stimulate the body's natural GH production.
GHK-Cu A tripeptide (three amino acids) naturally present in human plasma. When complexed with copper, it promotes wound healing, collagen synthesis, and anti-inflammatory effects.
GHRP (Growth Hormone Releasing Peptide) A class of peptides that stimulate GH release by acting on the ghrelin receptor. Includes GHRP-2, GHRP-6, Hexarelin, and Ipamorelin.
GLP-1 (Glucagon-Like Peptide-1) A hormone that regulates blood sugar and appetite. GLP-1 receptor agonists (Semaglutide, Tirzepatide, Retatrutide) mimic this hormone for weight management.
H
Half-Life The time it takes for half of a compound to be eliminated from the body. A longer half-life means less frequent dosing. CJC-1295 with DAC has a half-life of 6-8 days; without DAC, about 30 minutes.
HPLC (High-Performance Liquid Chromatography) A laboratory technique used to measure peptide purity. HPLC purity above 98% is considered acceptable for research peptides. Above 99% is excellent.
I
IGF-1 (Insulin-Like Growth Factor 1) A hormone produced primarily by the liver in response to growth hormone. IGF-1 blood levels are the primary biomarker for assessing whether GH peptides are working.
Intramuscular (IM) Injection into muscle tissue, typically using a longer needle (25-27 gauge, 1-1.5 inches). Less common for peptides than subcutaneous injection.
L
Lipodystrophy Changes in fat tissue caused by repeated injections in the same location. Can manifest as lumps (lipohypertrophy) or depressions (lipoatrophy). Prevented by proper site rotation.
Lyophilized Freeze-dried. Peptides are sold in lyophilized (powder) form for stability. They must be reconstituted with BAC water before use.
M
Mass Spectrometry A laboratory technique that confirms the molecular identity of a peptide by measuring its mass-to-charge ratio. An important verification on a COA alongside HPLC.
Mechanism of Action How a compound produces its biological effects. BPC-157's mechanism of action includes promoting angiogenesis, modulating nitric oxide, and upregulating growth factor receptors.
N
Neuroprotective Protecting nerve cells from damage or degeneration. Semax and Selank are neuroprotective peptides that support brain health through BDNF modulation.
P
Peptide A short chain of amino acids (typically 2-50) linked by peptide bonds. Smaller than proteins but larger than individual amino acids. They act as signaling molecules in the body.
Pharmacokinetics How the body absorbs, distributes, metabolizes, and eliminates a compound over time. Determines dosing frequency and route of administration.
Protocol A structured plan for using peptide compounds, including which compounds, doses, frequencies, routes, and cycle lengths. In PepOS, a protocol is your tracked plan.
R
Receptor A protein on cell surfaces that binds to specific molecules (like peptides) to trigger a biological response. GLP-1 receptors, ghrelin receptors, and melanocortin receptors are examples relevant to peptide use.
Reconstitution The process of dissolving lyophilized (freeze-dried) peptide powder in bacteriostatic water to create an injectable solution.
S
Secretagogue A substance that stimulates the secretion of another substance. GH secretagogues stimulate growth hormone secretion from the pituitary gland.
Stack Two or more peptide compounds used together in a protocol for synergistic effects. Example: the "Wolverine Stack" (BPC-157 + TB-500).
Subcutaneous (SubQ/SC) Injection into the fat layer just beneath the skin. The standard administration route for most peptides. Uses thin, short needles (29-31 gauge insulin syringes).
T
Tachyphylaxis Rapid decrease in response to a drug after repeated doses. Similar to desensitization. Common reason for cycling peptides.
Titration Gradually increasing the dose of a compound over time. Standard practice for GLP-1 agonists to minimize side effects.
V
Vial The glass container holding lyophilized peptide powder. Sealed with a rubber stopper and aluminum crimp cap. Typical sizes: 2mg, 5mg, 10mg.
This glossary covers the most common terms you will encounter in the PepOS app and peptide community. For compound-specific information, browse the 260+ profiles in the PepOS Library.
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Educational content only. Not medical advice. Consult a healthcare professional before starting any protocol.
