Glossary

Peptide research terms, plainly defined

Every technical term used on this site, in alphabetical order. Dotted underlines across the site link back to these definitions.

A

Agonist: A compound that binds to a cell receptor and activates it, producing a biological response. The opposite of an antagonist.
Amino acid: The chemical building block of peptides and proteins. Peptides are short chains of amino acids linked together by peptide bonds.
Anabolic: Describes processes that build tissue, such as muscle protein synthesis. Anabolic pathways are a common subject of growth-hormone-axis research.
Antagonist: A compound that binds to a cell receptor and blocks it, preventing activation. The opposite of an agonist.

BAC water (bacteriostatic water): Sterile water containing 0.9% benzyl alcohol, which suppresses bacterial growth. It is the standard diluent used to reconstitute lyophilized peptides for multi-dose research vials.
Bioavailability: The fraction of a compound that reaches circulation intact after administration. Injection routes typically show much higher bioavailability than oral or nasal routes for peptides.

COA (Certificate of Analysis): A lab document reporting what a specific batch actually contains — typically purity by HPLC and identity by mass spectrometry. Reputable research vendors publish batch-specific COAs.
Cycle: A defined period of repeated dosing followed by a break, as described in research protocols — for example, 8 weeks on, 4 weeks off.

GH (growth hormone): A hormone produced by the pituitary gland involved in growth, metabolism, and tissue repair. Several research peptides are studied for their ability to stimulate GH release.
GLP-1 (glucagon-like peptide-1): A gut hormone that stimulates insulin release, slows stomach emptying, and reduces appetite. GLP-1 receptor agonists such as semaglutide are studied and prescribed for metabolic regulation.

Half-life: How long it takes for half of a compound to be eliminated from the body. Half-life determines how often researchers dose a compound in protocols.
HPLC (high-performance liquid chromatography): A laboratory technique that separates the components of a sample to measure purity. The standard method used on peptide COAs to report a purity percentage.

IGF-1 (insulin-like growth factor 1): A hormone produced mainly by the liver in response to growth hormone. IGF-1 levels are a common downstream marker in GH-axis research.
Insulin unit (IU marking): The unit markings on an insulin syringe. On a U-100 syringe, 100 units equal 1 mL, so each unit equals 0.01 mL.
Intramuscular (IM): An injection into muscle tissue, deeper than a subcutaneous injection. Some research protocols reference IM administration for certain compounds.

Lyophilization: The freeze-drying process that removes water from a peptide solution under vacuum, leaving a stable powder that can survive shipping and storage.
Lyophilized: Freeze-dried. Peptides are shipped as a lyophilized powder ('puck') because the dry form is far more stable than a solution. It must be reconstituted before use in research.

Mechanism of action: How a compound produces its effects at the biological level — which receptors it binds, which pathways it activates or blocks.
Microgram (mcg / µg): One millionth of a gram, or one thousandth of a milligram. Most peptide research doses are measured in micrograms.
Milligram (mg): One thousandth of a gram. Peptide vials are typically labeled by total milligram content (for example, a 5 mg vial).

Nanogram (ng): One billionth of a gram. Used mostly in lab assay results rather than dosing figures.

PCT (post-cycle therapy): A protocol concept from anabolic-compound communities describing steps taken after a cycle to restore baseline hormone function. Rarely relevant to most peptides, which typically do not suppress natural hormone production the way steroids do.
Peptide: A short chain of amino acids — typically 2 to 50 — linked by peptide bonds. Peptides act as signaling molecules, telling cells and systems what to do, which is why they are widely studied in research.
Peptide bond: The chemical bond linking one amino acid to the next in a peptide chain.
Peptide stack: Two or more peptides used together in a research protocol because their mechanisms are complementary — for example, BPC-157 with TB-500.

Receptor: A protein on or inside a cell that binds specific signaling molecules and triggers a response. Most peptides work by binding particular receptors.
Reconstitution: The process of mixing a freeze-dried (lyophilized) peptide powder with bacteriostatic water to create a solution of known concentration.
RUO (Research Use Only): A regulatory classification meaning a product is sold strictly for laboratory research and is not approved, labeled, or intended for human or veterinary use.

Subcutaneous (SubQ): An injection into the fatty tissue just below the skin. The most commonly referenced administration route in peptide research literature.

Titration: Starting at a low dose and increasing gradually on a schedule. Research protocols titrate to assess tolerance — 'start low, go slow.'

U-100 syringe: An insulin syringe calibrated so that 100 units equal 1 mL. The standard syringe referenced in peptide research; each unit equals 0.01 mL.

Vial: The small sealed glass container peptides are supplied in, topped with a rubber septum that a syringe needle can pass through.

Put the vocabulary to work: the free calculator handles reconstitution and dosing numbers for any vial.