Peptide Glossary - 40+ Key Terms and Definitions

A comprehensive glossary of peptide-related terms, from basic concepts to advanced pharmacology. Whether you're new to peptide research or an experienced user, this reference covers essential vocabulary for understanding peptide dosing, reconstitution, and storage.

Biology

Angiogenesis: The formation of new blood vessels from existing ones. Many healing peptides like BPC-157 promote angiogenesis to accelerate tissue repair by improving blood supply to damaged areas.
Cortisol: A stress hormone produced by the adrenal glands. Some GH peptides like GHRP-2 and GHRP-6 can slightly elevate cortisol levels, while ipamorelin does not.
Denaturing: The process by which a peptide loses its three-dimensional structure and biological activity. Can be caused by shaking, excessive heat, freezing (after reconstitution), or UV light exposure.
GH (Growth Hormone): A hormone produced by the pituitary gland that stimulates growth, cell reproduction, and regeneration. GH secretagogue peptides stimulate the body's natural GH production.
GLP-1 (Glucagon-Like Peptide-1): A gut hormone that regulates appetite, blood sugar, and gastric emptying. GLP-1 agonists like semaglutide and tirzepatide mimic this hormone for weight management.

Dosing

Concentration: The amount of peptide dissolved per unit of liquid, typically expressed as mcg per unit or mg per ml. Calculated by dividing the total peptide amount by the volume of water added.
Loading Phase: An initial period of higher dosing to achieve therapeutic levels quickly. Common with TB-500 (4-6 weeks of higher doses before transitioning to maintenance).
Maintenance Dose: A lower dose used after the loading phase to sustain therapeutic levels. Typically 50-75% of the loading dose, taken less frequently.
mcg (Microgram): One millionth of a gram (1/1,000,000g) or one thousandth of a milligram. Most peptide doses are measured in micrograms. 1 mg = 1,000 mcg.
Reconstitution: The process of adding bacteriostatic water to lyophilized peptide powder to create an injectable solution. Always inject water slowly along the vial wall - never spray directly on the powder.
Subcutaneous Injection: An injection into the fatty tissue layer just beneath the skin. The most common administration method for peptides, typically using a 29-31 gauge insulin syringe at a 45-90 degree angle.
Titration: The process of gradually increasing a medication dose over time. Essential for GLP-1 agonists to minimize gastrointestinal side effects. Typically involves increasing the dose every 4 weeks.
Units (on insulin syringe): The measurement markings on an insulin syringe. 100 units = 1 ml. When dosing peptides, 'units to inject' refers to how far to draw back the plunger based on the peptide concentration.

Peptide

BPC-157: Body Protection Compound-157, a 15-amino acid peptide derived from human gastric juice. Widely researched for tissue healing, tendon repair, and gut protection.
CJC-1295: A synthetic analog of growth hormone releasing hormone (GHRH). Available in two forms: with DAC (long-acting, dosed weekly) and without DAC/Mod GRF 1-29 (short-acting, dosed 2-3x daily).
GHRH (Growth Hormone Releasing Hormone): A category of peptides that amplify growth hormone pulses. Examples include CJC-1295 and Sermorelin. Most effective when combined with a GHRP.
GHRP (Growth Hormone Releasing Peptide): A category of peptides that trigger growth hormone release from the pituitary gland. Examples include Ipamorelin, GHRP-2, and GHRP-6.
Ipamorelin: A selective growth hormone secretagogue (GHRP) known for being the 'cleanest' GH peptide with no significant effects on cortisol, prolactin, or appetite.
Semaglutide: A GLP-1 receptor agonist used for weight management and type 2 diabetes. The active ingredient in brand-name medications Ozempic and Wegovy. Administered once weekly.
TB-500 (Thymosin Beta-4): A synthetic version of the naturally occurring 43-amino acid peptide Thymosin Beta-4. Works systemically to promote healing by upregulating actin and promoting cell migration.
Tirzepatide: A dual GLP-1/GIP receptor agonist for weight management and type 2 diabetes. Clinical trials showed up to 22.5% body weight reduction. Brand names include Mounjaro and Zepbound.

Pharmacology

Bioavailability: The proportion of a substance that enters the bloodstream and is available to produce an active effect. Subcutaneous injection provides near-complete bioavailability for most peptides.
DAC (Drug Affinity Complex): A chemical modification added to CJC-1295 that extends its half-life from minutes to about 8 days by binding to serum albumin in the blood.
Dose-Response Curve: The relationship between the amount of peptide administered and the magnitude of its effect. Higher doses don't always mean better results and can sometimes cause diminishing returns.
Half-Life: The time it takes for half of a substance to be eliminated from the body. Determines dosing frequency - shorter half-life peptides need more frequent dosing.
Secretagogue: A substance that promotes the secretion of a hormone. GH secretagogues stimulate the pituitary gland to release growth hormone naturally, unlike exogenous HGH which directly introduces the hormone.

Quality

Certificate of Analysis (COA): A document from a testing laboratory confirming the purity, identity, and quality of a peptide product. Reputable vendors provide COAs for each batch, ideally from third-party labs.
HPLC (High-Performance Liquid Chromatography): The gold standard analytical method for measuring peptide purity. Separates components of a sample to determine what percentage is the desired peptide vs. impurities. Look for 98%+ purity.
Mass Spectrometry (MS): An analytical technique that identifies compounds by their molecular weight. Used alongside HPLC to confirm that a peptide is actually what the label claims.

Supplies

Bacteriostatic Water (BAC Water): Sterile water containing 0.9% benzyl alcohol as a preservative. Used to reconstitute peptides because it inhibits bacterial growth, extending the shelf life of mixed peptides to 3-4 weeks.
Insulin Syringe: A syringe calibrated in 'units' (typically 100 units = 1ml) used for subcutaneous injections. Available in 0.3ml, 0.5ml, and 1ml sizes with 29-31 gauge needles.
Lyophilized (Freeze-Dried): The powder form of peptides as they arrive from the manufacturer. Lyophilized peptides are stable for extended storage and must be reconstituted with bacteriostatic water before use.