Peptide Glossary
Definitions of key terms used across PeptideStack. 30 terms.
A
- ACE Inhibitor
- Angiotensin-converting enzyme inhibitor. Some bioactive peptides from food (dairy, eggs) have mild ACE-inhibitory properties that may support cardiovascular health.
- 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. Peptides like BPC-157 promote angiogenesis, which accelerates tissue healing by improving blood supply to damaged areas.
B
- Bacteriostatic Water
- Sterile water containing 0.9% benzyl alcohol, used to reconstitute peptides. The benzyl alcohol inhibits bacterial growth, extending the shelf life of the reconstituted solution to 4–6 weeks. See our reconstitution calculator.
- Bioavailability
- The proportion of a substance that enters the bloodstream and has an active effect. Injectable peptides have near-100% bioavailability; oral peptides often have very low bioavailability due to digestive breakdown.
C
- Category 2 Bulk Drug
- An FDA classification for substances that cannot be used by compounding pharmacies. BPC-157 was placed in this category in late 2023, restricting its availability in the US.
- COA (Certificate of Analysis)
- A document from a third-party lab verifying the purity, identity, and potency of a peptide product. Always request COAs when purchasing research peptides.
- Compounding Pharmacy
- A pharmacy that custom-prepares medications. Compounded peptides (like compounded semaglutide) are prepared by these pharmacies, often at lower cost than brand-name versions.
G
- GH (Growth Hormone)
- A peptide hormone produced by the pituitary gland. It promotes growth, cell repair, and metabolism. Many peptides (Ipamorelin, CJC-1295, Sermorelin) work by stimulating GH release.
- GHRH
- Growth Hormone-Releasing Hormone. A natural hormone that signals the pituitary to release GH. Peptides like CJC-1295 and Sermorelin mimic GHRH.
- GIP
- Glucose-dependent Insulinotropic Polypeptide. A gut hormone that enhances insulin secretion. Tirzepatide targets both GLP-1 and GIP receptors.
- GLP-1
- Glucagon-Like Peptide-1. A gut hormone that reduces appetite, slows digestion, and improves insulin sensitivity. Semaglutide (Ozempic) and tirzepatide (Mounjaro) are GLP-1 receptor agonists.
H
- Half-Life
- The time it takes for half of a peptide dose to be eliminated from the body. Shorter half-life = more frequent dosing. Ipamorelin has a ~2 hour half-life; CJC-1295 with DAC has a ~6-8 day half-life.
- HPLC
- High-Performance Liquid Chromatography. An analytical method used to verify peptide purity. COAs should show HPLC purity ≥98% for research-grade peptides.
I
- IGF-1
- Insulin-like Growth Factor 1. A hormone produced by the liver in response to growth hormone. It directly promotes cell growth and muscle protein synthesis. See IGF-1 LR3 & DES.
- Intramuscular (IM)
- Injection into muscle tissue. Less common for peptides than subcutaneous injection, but used for some compounds.
- Intranasal
- Administration through the nasal passages. Used for neuropeptides like Selank and Semax to bypass the blood-brain barrier.
- IU (International Unit)
- A measurement of biological activity, not weight. The conversion to mg varies by compound (e.g., 1mg HGH ≈ 3 IU). Use our unit converter for accurate conversions.
L
- Lyophilized
- Freeze-dried. Most peptides are sold as lyophilized powder that must be reconstituted with bacteriostatic water before use. Lyophilized peptides can be stored for months to years.
M
- mcg (Microgram)
- One-millionth of a gram, or one-thousandth of a milligram. Most peptide doses are measured in micrograms. 1 mg = 1,000 mcg. Convert units with our unit converter.
- mg (Milligram)
- One-thousandth of a gram. Peptide vial sizes are typically measured in milligrams (e.g., a 5mg or 10mg vial). Convert units with our unit converter.
- Myostatin
- A protein that limits muscle growth. Follistatin binds to and inhibits myostatin, theoretically allowing greater muscle development.
P
- PCT (Post-Cycle Therapy)
- A protocol to restore natural hormone production after using suppressive compounds. Unlike steroids, most peptides do not require PCT because they work with (not replace) natural hormone production.
- Peptide Bond
- The chemical bond linking amino acids together in a peptide chain. Formed between the carboxyl group of one amino acid and the amino group of the next.
R
- Reconstitution
- The process of dissolving lyophilized (freeze-dried) peptide powder in bacteriostatic water. Use our reconstitution calculator for exact measurements.
S
- Secretagogue
- A substance that stimulates the secretion of a hormone. Growth hormone secretagogues (Ipamorelin, GHRP-2, MK-677) stimulate the pituitary to release GH.
- SNARE Complex
- A protein complex that enables neurotransmitter release at nerve endings. Argireline (a skincare peptide) works by disrupting SNARE complex assembly, reducing muscle contractions that cause wrinkles.
- Subcutaneous (SubQ)
- Injection into the fat layer just beneath the skin. The most common administration route for peptides, using a small insulin syringe (29-31 gauge needle).
T
- Titration
- Gradually increasing a dose over time to minimize side effects. GLP-1 peptides like semaglutide require a specific titration schedule over several weeks.
W
- WADA
- World Anti-Doping Agency. The international body that maintains the prohibited substance list for competitive sports. Many peptides (GH secretagogues, BPC-157, TB-500) are WADA-banned.