Reference

Peptide Glossary

Name: Dr Jays Peptides
Address: 6593 Powers Avenue Suite 19, Jacksonville, FL, US
Telephone: +1-904-678-5215

122 plain-English definitions of peptide, endocrine, and biotech terms.

A

Agonist: A molecule that activates a receptor.; Agonists bind a receptor and trigger its biological response. GLP-1 receptor agonists like semaglutide are the classic example.
Allosteric Modulator: Binds a receptor at a site other than the active one to change its behavior.
Amino Acid: The building blocks that link together to form peptides and proteins.
AMPK: Energy-sensing enzyme that switches on when ATP runs low; central to metabolic and longevity research.
Angiogenesis: The growth of new blood vessels from existing ones.
Antagonist: A molecule that blocks a receptor.; Antagonists bind a receptor but don't activate it — they prevent the natural agonist from working.
Antioxidant: A molecule that neutralizes reactive oxygen species (ROS).
Apoptosis: Programmed cell death — a clean, controlled cellular suicide pathway.
Autophagy: Cellular recycling — the body breaks down and reuses damaged components.

B

Bacteriostatic Water: Sterile water with 0.9% benzyl alcohol used to reconstitute peptide powders.
BDNF: Brain-Derived Neurotrophic Factor — supports neuron growth and synapse plasticity.
Bioavailability: The fraction of a dose that actually reaches systemic circulation.
Bioregulator Peptide: Short peptides (often 2–4 amino acids) studied for tissue-specific gene-expression regulation.
Blood-Brain Barrier (BBB): A selective filter protecting the brain from molecules in the blood.
Buffer: A solution that resists pH change; used to stabilize peptide formulations.

C

CAGR: Calorie-restriction-mimicking compounds — substances that mimic the metabolic effects of fasting.
cAMP: Cyclic AMP — an intracellular second messenger that relays receptor signals.
Catabolic: A state of tissue breakdown (opposite of anabolic).
Collagen: Structural protein in skin, tendons, bones, and connective tissue.
Cortisol: Primary glucocorticoid stress hormone produced by the adrenal cortex.
Cytokine: Small signaling proteins (often peptides) used by immune cells to communicate.

D

DAC (Drug Affinity Complex): A modification that lets a peptide bind albumin, dramatically extending half-life.
Desensitization: When receptors downregulate after repeated exposure, blunting response.
DNA Methylation: Chemical tags on DNA that turn genes on or off; biomarker for biological age.
Dose-Response: The relationship between dose and biological effect.
Downregulation: When a cell reduces the number of receptors on its surface in response to overstimulation.

E

Edema: Swelling caused by fluid trapped in tissues.
Endogenous: Produced inside the body (opposite of exogenous).
Endothelium: The single-cell layer lining blood vessels.
Enzyme: A protein catalyst that speeds up a biological reaction.
Exogenous: Introduced from outside the body (a peptide injection, for example).

F

FoxO: Forkhead transcription factor family; central to stress resistance and longevity pathways.
Free Radical: Reactive molecule with an unpaired electron; oxidizes other molecules.

G

Gene Expression: How DNA is read out to make proteins; can be turned up or down by signaling peptides.
Ghrelin: The hunger hormone; GHRPs mimic its action at the GHS-R receptor.
GHRH: Growth Hormone Releasing Hormone — hypothalamic peptide that tells the pituitary to make GH.
GHRP: Growth Hormone Releasing Peptide — synthetic ghrelin mimetic.
GHS-R: Growth Hormone Secretagogue Receptor — the ghrelin receptor; target of GHRPs.
GIP: Glucose-dependent Insulinotropic Polypeptide — second incretin; co-targeted by tirzepatide.
GLP-1: Glucagon-Like Peptide-1 — incretin hormone that controls glucose, satiety, and gastric emptying.
Glucagon: Pancreatic hormone that raises blood glucose; triple agonists like retatrutide hit its receptor too.
Glycation: When sugars react with proteins to form AGEs (advanced glycation end-products); a hallmark of aging.
Growth Hormone (GH): Pituitary hormone driving growth, repair, and lipolysis.

H

Half-Life: Time it takes for half of a compound to be cleared from the body.
HPA Axis: Hypothalamic-Pituitary-Adrenal axis — the body's central stress-response system.
HPG Axis: Hypothalamic-Pituitary-Gonadal axis — controls reproductive hormones.
HPLC: High-Performance Liquid Chromatography — the standard purity test for research peptides.
Hypertrophy: Growth in size of cells or tissue (e.g., muscle fibers).

I

IGF-1: Insulin-like Growth Factor 1 — anabolic peptide produced mostly by the liver in response to GH.
Incretin: Gut hormones (GLP-1, GIP) that amplify insulin release after meals.
Inflammation: The body's response to injury or infection; chronic inflammation drives most age-related disease.
Insulin: Pancreatic hormone that pulls glucose out of blood into cells.
Insulin Sensitivity: How well cells respond to insulin. High sensitivity = small amounts of insulin work fine.
Intramuscular (IM): Injection directly into muscle tissue.
Ion Channel: A membrane protein that lets ions cross a cell membrane on cue.

K

Ketone: Energy molecule produced by the liver from fat during low-carb states.
Kisspeptin: Upstream regulator of GnRH; master switch for puberty and reproductive function.

L

Leptin: Adipose-derived hormone signaling energy stores and satiety to the brain.
Ligand: Any molecule that binds a receptor.
Lipolysis: The breakdown of stored fat into free fatty acids.
Lyophilized: Freeze-dried. Peptides ship lyophilized to maximize shelf life.

M

Mast Cell: Immune cell that releases histamine; involved in allergy and certain peptide reactions.
MC4R: Melanocortin-4 receptor — central regulator of appetite and libido.
Mitochondria: The cellular power plants that produce ATP via oxidative phosphorylation.
MOTS-c: Mitochondrial-Derived Peptide encoded in mtDNA; metabolic regulator.
mTOR: Mechanistic Target of Rapamycin — central growth/protein-synthesis switch; inhibition is a longevity strategy.
Myostatin: TGF-β family protein that limits muscle growth; antagonists are an active research area.

N

NAD+: Nicotinamide Adenine Dinucleotide — central coenzyme in energy metabolism and sirtuin signaling.
Neurogenesis: Formation of new neurons; happens mainly in the hippocampus in adults.
Neuroplasticity: The brain's ability to rewire itself by forming new neural connections.
Neurotransmitter: Chemical messenger released between neurons (dopamine, serotonin, GABA, etc.).
NF-κB: Master inflammatory transcription factor.
NO (Nitric Oxide): Gaseous signaling molecule; dilates blood vessels and is central to vascular research.
Nootropic: Compound studied for cognitive enhancement.

O

Olfactory: Relating to the sense of smell; intranasal peptides can reach the brain via the olfactory mucosa.
Oxidative Stress: Imbalance between free radicals and antioxidants; a driver of aging and disease.
Oxytocin: Hypothalamic neuropeptide central to bonding, trust, and labor contractions.

P

Pegylation: Attaching PEG chains to a peptide to extend its half-life and reduce immune clearance.
Peptide: A short chain of amino acids linked by peptide bonds (typically 2–50).
Peptide Bond: The amide bond joining one amino acid's carboxyl group to the next amino acid's amino group.
Pharmacodynamics: What a drug does to the body.
Pharmacokinetics: What the body does to a drug — absorption, distribution, metabolism, elimination.
Pituitary: Pea-sized gland at the base of the brain that releases GH, ACTH, FSH, LH, and more.
Placebo: An inert substance used as a control in clinical research.
Polyethylene Glycol (PEG): Inert polymer attached to peptides to extend half-life (see Pegylation).
Potency: Amount of compound required to produce a given effect.
Prohormone: An inactive precursor converted into an active hormone.
Prolactin: Pituitary hormone involved in lactation; can be raised by certain GHRPs.
Protein: A long chain of amino acids folded into a 3D shape; longer than a peptide.
Pulsatile Release: Release in discrete bursts (e.g., GH) rather than continuously.
Purity: Percentage of a sample that is the intended peptide; research-grade is typically ≥98% by HPLC.

R

Receptor: A protein that binds a specific molecule and triggers a cellular response.
Reconstitution: Mixing lyophilized peptide powder with bacteriostatic water to create an injectable solution.
ROS: Reactive Oxygen Species — oxidative byproducts of metabolism.

S

Satiety: The feeling of fullness that ends a meal.
Secretagogue: A substance that causes another substance to be secreted (e.g., GH secretagogues).
Senescent Cell: Cell that has stopped dividing but won't die; accumulates with age and drives inflammation.
Senolytic: Compound that selectively clears senescent cells.
SHBG: Sex Hormone Binding Globulin — carries testosterone and estradiol in blood.
Signal Transduction: The cascade by which a receptor's activation translates into a cellular response.
Sirtuins: NAD+-dependent enzymes (SIRT1–7) linked to metabolism and longevity.
Solubility: How well a peptide dissolves; affects which reconstitution diluent is used.
Somatostatin: Hypothalamic peptide that inhibits GH release; the brake on the GH system.
Stack: A combination of two or more peptides studied together.
Stem Cell: Undifferentiated cell that can divide and become specialized cell types.
Subcutaneous (SubQ): Injection into the fat layer just under the skin.
Synapse: The junction where one neuron passes a signal to another.
Synthesis: How peptides are chemically built — usually solid-phase peptide synthesis (SPPS).

T

Tachyphylaxis: Rapid loss of response after repeated dosing; a form of acute desensitization.
Telomerase: Enzyme that rebuilds telomeres; epitalon is studied for telomerase activation.
Telomere: Protective DNA caps on chromosomes that shorten with each cell division.
Thymus: Immune-system gland where T-cells mature; shrinks with age.
Tolerance: Decreased response after repeated dosing — see also Tachyphylaxis and Desensitization.
Topical: Applied to the skin (cosmetic peptide research).
Transcription Factor: Protein that controls which genes get expressed.
Tropic Hormone: Hormone that stimulates another endocrine gland (e.g., ACTH stimulates the adrenal).
Truncal Fat: Fat stored around the midsection; reduction is studied with tesamorelin.

U

Upregulation: Cellular increase in receptor numbers or gene expression.

V

VEGF: Vascular Endothelial Growth Factor — drives angiogenesis.
VIP: Vasoactive Intestinal Peptide — broad-acting neuropeptide and immune modulator.

W

WADA: World Anti-Doping Agency — maintains the prohibited substances list in sport.
Withdrawal: Symptoms that appear when a compound is discontinued after the body adapts to it.