Glossary

Also: 503A · 503A pharmacy

Patient-specific compounding by a state-licensed pharmacy, the legal lane that has dominated peptide compounding in the US.

Also: 503B

An FDA-registered facility that compounds without patient-specific prescriptions, the second compounding lane, used for office stock.

Also: R_acc · accumulation factor

The factor by which steady-state peak exceeds single-dose peak, a function of dose interval and half-life.

Also: acetate

A common counter-ion form for peptides, generally preferred over TFA salt for human use because acetate is non-toxic.

Also: ACh · cholinergic

The neurotransmitter at the neuromuscular junction and many CNS synapses. Cosmetic peptides like Argireline and SNAP-8 work by blocking its release at facial muscle endings.

A protein that forms the cytoskeleton, the internal scaffolding of every cell. TB-500 binds and regulates actin to drive tissue repair and cell migration.

Also: activins

A TGF-β-family signaling protein that suppresses muscle growth and regulates several reproductive axes; antagonized by follistatin alongside myostatin.

Also: adipocytes · fat cell · fat cells

A fat cell, the storage unit for triglycerides and the source of leptin.

Also: adverse events

Any unwanted clinical event during drug exposure, collected systematically in trials and post-marketing surveillance.

Also: agonists

A molecule that activates a receptor and triggers its downstream signal.

Also: albumin

A half-life-extension strategy where a fatty acid or DAC tag on the peptide reversibly binds circulating albumin, used by semaglutide, liraglutide, and CJC-1295-DAC.

A molecule that binds a receptor at a site other than the main ligand-binding pocket, tuning the response up or down.

Also: AA · amino acids · residue · residues

The 20 building blocks of proteins and peptides, strung together by peptide bonds in a defined sequence.

AMP-activated protein kinase, a cellular energy sensor that switches on fat-burning, glucose uptake, and mitochondrial biogenesis when energy is low. MOTS-c works largely through AMPK.

A hormone co-secreted with insulin from pancreatic beta cells that slows gastric emptying and reduces appetite. Cagrilintide and pramlintide are amylin analogs used alongside GLP-1 agonists for weight loss.

Also: analogue · analogs · analogues

A modified version of a natural molecule, same general structure, tweaked for stability, potency, or duration.

Also: anecdote · anecdotes

Evidence from individual user reports rather than controlled trials, the lowest-confidence tier on this site.

The growth of new blood vessels, central to wound healing and the proposed mechanism of BPC-157 and TB-500.

Also: antagonists

A molecule that binds a receptor without activating it, blocking the natural signal.

Also: antimicrobial peptide · AMP

Killing or inhibiting microorganisms (bacteria, fungi, viruses). LL-37 is a cathelicidin antimicrobial peptide that disrupts bacterial membranes as part of innate immunity.

A molecule that neutralizes reactive oxygen species before they damage DNA, proteins, or lipids. Glutathione is the body's main intracellular antioxidant; GHK-Cu and certain Khavinson peptides have antioxidant activity.

Anxiety-reducing. Selank's anxiolytic effect is its lead indication in Russian clinical use; tuftsin-derived peptides bind GABAergic and serotonergic systems.

Programmed cell death, a regulated process distinct from injury-driven necrosis.

Also: atypical mole

An irregularly shaped, oddly pigmented mole that can be a precursor to melanoma. Chronic melanocortin exposure (especially Melanotan II) carries a documented signal for mole darkening and atypical-nevus formation.

Also: BAC water · BAC-water · bacteriostatic · bac

Sterile water with 0.9% benzyl alcohol, the standard diluent for lyophilized peptides intended for multi-day use.

Also: Brain-Derived Neurotrophic Factor

The most-studied neurotrophin; drives neurogenesis, synaptic plasticity, and long-term memory consolidation. Upregulated by Semax, Selank, exercise, and several nootropic peptides.

How tightly a molecule sticks to its receptor, usually expressed as an IC50, EC50, or Kd value.

The fraction of a dose that reaches the bloodstream intact.

Also: boxed warning

The FDA's strongest label warning, reserved for serious or life-threatening risks. GLP-1s carry one for thyroid C-cell tumors based on rodent data.

Also: blends · blended

Two or more compounds pre-mixed and dispensed as a single product, different from a stack, where the user combines separately-vialed compounds at administration time.

Folk knowledge passed around forums and gym communities, often plausible-sounding but rarely traceable to peer-reviewed evidence.

The carboxyl end of a peptide chain. C-terminal fragments often retain a parent hormone's biology in a smaller, more drug-like form, AOD-9604 is the C-terminal 16-aa fragment of hGH, KPV is the C-terminal tripeptide of α-MSH.

A phospholipid concentrated in the inner mitochondrial membrane. SS-31 (elamipretide) binds cardiolipin to stabilize electron-transport-chain assembly and preserve mitochondrial function under stress.

Also: cardiomyopathies

Disease of the heart muscle. Several peptides (BPC-157, hexarelin, MOTS-c) have shown cardioprotective effects in cardiomyopathy models.

Also: COA

The lab-issued document that reports a vial's HPLC purity, mass-spec identity, and counter-ion content, the primary quality artifact for research peptides.

Also: circadian rhythm

Following a ~24-hour biological cycle of activity, hormone release, body temperature, and sleep-wake. Epitalon and Pinealon are described as supporting circadian regulation via pineal/melatonin pathways; DSIP times to the rhythm's nighttime phase.

Also: Phase 1 · Phase 2 · Phase 3 · phase I · phase II · phase III

A regulated human study of a drug, Phase 1 (safety), Phase 2 (efficacy and dose-finding), and Phase 3 (large-scale efficacy and safety).

A non-protein molecule that an enzyme requires to function, often a vitamin derivative or nucleotide. NAD+ is a coenzyme for sirtuins and PARPs; without it those enzymes can't catalyze their redox and DNA-repair reactions.

An end-to-end refrigerated handling pipeline, relevant for peptides shipped reconstituted or for long-term storage of sensitive compounds.

Also: collagen turnover · extracellular matrix remodeling · ECM remodeling

The continuous breakdown and re-synthesis of collagen by fibroblasts and matrix metalloproteinases, the process cosmetic peptides try to bias toward synthesis.

Also: compounding pharmacies

A pharmacy that prepares custom-formulated medications for individual patients, the regulated source for peptides not available as commercial drugs.

Also: contraindicated · contraindications

A condition or co-administered drug under which a compound should not be used, typically because the risk clearly outweighs any benefit.

The body's primary stress hormone, released from the adrenal cortex. Some GHRPs (GHRP-2, GHRP-6, hexarelin) cause a modest cortisol rise alongside the desired GH pulse; Ipamorelin is preferred because it does not.

Also: cycling · cycled

A defined run of dosing followed by a planned break, used to avoid tachyphylaxis or chronic suppression.

Protecting cells from injury or stress without targeting one specific receptor or pathway. BPC-157 and Humanin are described as cytoprotective because they preserve tissue function across mechanical, ischemic, and chemical insults.

Also: Drug Affinity Complex · DAC:GRF

Drug Affinity Complex, a maleimide modification that lets a peptide covalently attach to circulating albumin, extending its half-life from minutes to days.

Also: Da · Daltons · kDa · kilodalton · kilodaltons

The unit for molecular mass, 1 Da is roughly the mass of a single hydrogen atom.

The liquid (usually bacteriostatic water) used to dissolve a lyophilized peptide before injection.

A neurotransmitter central to motivation, reward, motor control, and prolactin suppression. Semax modulates dopaminergic systems alongside BDNF/NGF upregulation; tesofensine inhibits dopamine reuptake.

When repeated stimulation causes the cell to physically remove receptors, blunting the response over time.

Also: drug-drug interaction · DDI

When one drug changes the effect, blood level, or risk profile of another, a standard concern for any stack of multiple compounds.

A stretchy connective-tissue protein that gives skin, lung, and blood vessels their recoil. Cosmetic peptides like Matrixyl, Pal-GHK, and Syn-Coll signal fibroblasts to upregulate collagen AND elastin synthesis for dermal remodeling.

Acting through hormones secreted into the bloodstream to affect distant tissues. Distinguished from paracrine (nearby cells) and autocrine (the same cell) signaling. Tirzepatide and Follistatin engage endocrine pathways; BPC-157 acts mostly locally.

Made naturally by the body. Endogenous GH refers to the body's own pituitary growth hormone (which GHRH/GHRP analogs stimulate); compare to exogenous (administered from outside).

Also: endothelial cells · endothelium

The single-cell layer lining blood-vessel interiors. Endothelial migration and proliferation are the cellular substrate of angiogenesis.

A small endogenous opioid peptide. Enkephalin-like activity contributes to Selank's anti-anxiety and immune effects; Pentapeptide-18 is engineered as an enkephalin mimetic for cosmetic neuromuscular relaxation.

The layer of cells lining surfaces and cavities throughout the body, skin, gut, airways. Mucosal-healing peptides (BPC-157, KPV, Bronchogen, Chonluten) all target epithelial repair.

Also: EPP

A rare inherited disorder where porphyrin buildup causes severe, painful skin reactions to light. Afamelanotide (Melanotan I / Scenesse) is FDA/EMA-approved specifically for EPP.

Also: ER · estrogen receptors · ERα · ERβ

The nuclear receptor for estrogen. SERMs like enclomiphene block hypothalamic ERs to relieve negative feedback on LH/FSH and raise endogenous testosterone.

Administered from outside the body, in contrast to endogenous (made internally). Exogenous testosterone shuts down endogenous LH and FSH; HCG and gonadorelin support endogenous production during TRT.

Also: 503A bulks list · bulk drug substance list

The FDA's catalog of active ingredients eligible for compounding, peptides not on it (or removed from it) cannot legally be compounded under 503A.

Also: FDA approved · FDA-approval

A drug that has cleared the FDA's review for at least one specific indication and can be legally prescribed for that use.

Also: fibroblasts

The dermal connective-tissue cell that synthesizes collagen, elastin, and ground substance, the primary target of cosmetic peptides.

Also: gamma-aminobutyric acid · gabaergic

The brain's main inhibitory neurotransmitter, counterweight to glutamate's excitation. Selank modulates GABA signaling for its anxiolytic effect, and a common misconception treats it like a benzodiazepine (which directly binds GABA-A receptors); Selank's mechanism is gentler and apparently doesn't cause tolerance or withdrawal.

Also: gastric motility

The rate at which food leaves the stomach. GLP-1 and GIP receptor agonists slow gastric emptying, prolonging satiety and blunting post-meal glucose spikes.

The 'hunger hormone', released from the stomach when empty and the natural ligand for the GHS receptor.

Also: Growth Hormone-Releasing Hormone · Growth Hormone Releasing Hormone

Growth hormone-releasing hormone, the hypothalamic peptide that prompts the pituitary to release HGH.

Also: Growth Hormone-Releasing Peptide · Growth Hormone Releasing Peptide

Growth hormone-releasing peptide, a synthetic ghrelin-mimetic class that triggers HGH release through a different receptor than GHRH.

Also: Growth Hormone Secretagogue

Growth hormone secretagogue, the umbrella class for compounds that trigger HGH release, including GHRPs and ghrelin mimetics.

Also: ghs-r · ghs-r1 · ghrelin receptor

Growth hormone secretagogue receptor 1a, the specific ghrelin receptor on pituitary somatotrophs. GHRPs (Ipamorelin, Hexarelin, GHRP-2/6) and MK-677 are all GHS-R1a agonists; saturating it with two GHRPs is the basis for the 'two GHRPs' avoid combination.

Also: Glucose-Dependent Insulinotropic Polypeptide · Gastric Inhibitory Polypeptide

Glucose-dependent insulinotropic polypeptide, a second incretin hormone, the GIP half of tirzepatide's dual mechanism.

Also: Glucagon-Like Peptide-1 · Glucagon-Like Peptide 1

Glucagon-like peptide-1, a gut hormone released after eating that drives insulin release, satiety, and slowed gastric emptying.

Insulin's counterpart, the pancreatic α-cell hormone that raises blood glucose by mobilizing liver glycogen.

Activity that only kicks in when blood glucose is elevated. GLP-1 receptor agonists stimulate insulin release in a glucose-dependent manner, which is why monotherapy rarely causes hypoglycemia, but stacking with insulin or non-dependent secretagogues (sulfonylureas) removes that safety margin.

Also: glycemic control

Pertaining to blood glucose. Glycemic control is the standard summary measure for diabetes treatments, captured as HbA1c, GLP-1 agonists, GIP/GLP-1 dual agonists, and metformin all improve glycemic control by complementary mechanisms.

A protein with covalently attached carbohydrate (glycan) chains. Follistatin is a glycoprotein with multiple isoforms (288, 315, 344 aa); glycosylation often controls half-life, distribution, and tissue specificity.

Also: glycosaminoglycans · GAGs · GAG

Long polysaccharide chains (e.g. hyaluronic acid, chondroitin sulfate) that hold water and structure in skin, cartilage, and connective tissue.

Also: G-protein-coupled receptor · G-protein coupled receptor · GPCRs

G-protein-coupled receptor, the largest family of cell-surface receptors and the target of most peptide drugs.

Also: grey market · gray-market

Vendors operating in legally ambiguous space, selling research-chemical-labelled peptides that are nonetheless used by humans.

The time it takes for the blood concentration of a drug to fall by half.

Also: glycated hemoglobin · a1c

Glycated hemoglobin, a blood marker that reflects average glucose levels over the prior ~3 months. HbA1c reduction is the standard primary endpoint for diabetes-treatment efficacy; every approved GLP-1 receptor agonist on this site is rated in part by its HbA1c effect.

Also: MDM2 · HDM-2

The human ubiquitin ligase that degrades the p53 tumor-suppressor protein. The PNC-27 peptide is designed to disrupt the HDM2–p53 interaction.

Pertaining to the liver. Hepatic fat reduction is a metric for mazdutide; hepatic lipid mobilization is one of the effects driving weight loss in glucagon-active multi-agonists like retatrutide.

Also: hepatoprotection

An effect that protects liver tissue from chemical, oxidative, or inflammatory damage.

A peptide that is exactly seven amino acids long. Pentapeptide-18 (5 aa) and tripeptide-29 (3 aa) are similarly named by chain length; heptapeptides include certain Khavinson short-peptide variants.

Also: Growth Hormone · Human Growth Hormone · GH · somatropin

Human growth hormone, the pituitary hormone that drives growth and metabolic effects, largely via IGF-1.

Also: hormones

A signaling molecule released by one tissue that travels through the bloodstream to act on a distant target tissue. Many peptides are hormones, but not all hormones are peptides.

Also: High-Performance Liquid Chromatography · HPLC purity

High-performance liquid chromatography, the standard analytical method for measuring peptide purity, typically reported as a percentage on the certificate of analysis.

Also: hypoactive sexual desire disorder

Hypoactive sexual desire disorder, clinically diagnosed low libido in premenopausal women. Bremelanotide (PT-141 / Vyleesi) is FDA-approved specifically for HSDD; the indication is the basis for distinguishing PT-141 from off-label Melanotan II use.

Cellular growth in size, as opposed to hyperplasia (growth in number). Skeletal-muscle hypertrophy is the dose-driven goal for IGF-1 LR3 and Follistatin protocols.

Dangerously low blood sugar. The risk is low with GLP-1 monotherapy because of the glucose-dependent mechanism, but rises sharply when GLP-1 agonists are combined with insulin, sulfonylureas, or other secretagogues, or when IGF-1 LR3 is dosed without timed carbohydrate.

The brain region that integrates body-state signals and instructs the pituitary which hormones to release.

Also: Insulin-Like Growth Factor 1 · Insulin-like Growth Factor-1

Insulin-like growth factor 1, the liver-produced hormone responsible for most of HGH's anabolic effects.

Also: IGF-1 receptor

The receptor for IGF-1 (insulin-like growth factor 1). Activated by IGF-1 itself and engineered analogs like IGF-1 LR3 and IGF-1 DES; downstream signaling drives muscle hypertrophy and anti-apoptotic effects.

Also: IGF-binding protein · IGF-binding proteins · IGFBP-3

Insulin-like growth factor binding proteins, a family of carriers (IGFBP-1 through -7) that regulate how much free IGF-1 reaches its receptor.

Also: interleukin-6

An inflammatory cytokine elevated in chronic inflammation, infection, and aging ('inflammaging'). Rigin suppresses fibroblast IL-6 secretion; Crystagen modulates IL-6 along with heat-shock expression, both targeting low-grade inflammation rather than acute infection.

Also: incretins

Gut hormones, primarily GLP-1 and GIP, that amplify insulin release after meals.

The observation that oral glucose triggers more insulin release than IV glucose at the same blood-sugar level, explained by gut-secreted GLP-1 and GIP. The phenomenon every incretin therapy is built on.

Also: Investigational New Drug

Investigational New Drug, an FDA authorization that lets a sponsor ship and study an unapproved drug in human trials.

The pancreatic hormone that drives glucose into cells and the central regulator of fuel partitioning.

Also: insulinotropic effect

Stimulating insulin secretion. Incretins (GLP-1, GIP) act in a glucose-dependent insulinotropic fashion, they only release insulin when blood sugar is elevated, limiting hypoglycemia risk.

Also: IM

Injected into muscle, faster absorption than subcutaneous, longer needles required.

Also: nasal spray

Delivered as a spray into the nasal cavity, where the peptide is absorbed through nasal mucosa.

A molecule that binds a receptor and pushes it below its baseline (resting) activity.

Also: Institutional Review Board

Institutional Review Board, the ethics committee that must approve any human research protocol before it can enroll subjects.

One of several closely related variants of the same protein, often produced by alternative splicing or proteolytic processing. Follistatin exists as a 288-aa precursor with 315-aa (circulating) and 344-aa (tissue-bound) isoforms with different biology.

Also: International Unit · International Units

International Unit, a biological-activity unit used for hormones like HGH, insulin, and HCG.

The hormone released by fat cells that signals satiety to the brain, broadly the opposite of ghrelin.

Also: luteinizing hormone receptor · lhcgr · lh/cg receptor

The receptor on testicular Leydig cells (in males) and ovarian theca/granulosa cells (in females) that responds to luteinizing hormone, and to HCG, which mimics LH well enough to be used clinically as an LH replacement. This is why HCG can sustain endogenous testosterone production during TRT.

Also: ligands

Any molecule that binds a receptor, hormone, neurotransmitter, drug, or peptide.

Also: lipodystrophic

Abnormal fat distribution or loss, most relevant here as the FDA-approved indication for tesamorelin (HIV-associated lipodystrophy with excess visceral abdominal fat).

The breakdown of stored fat into free fatty acids, the metabolic step targeted by HGH and several GHRPs.

A peptide chemically modified with a lipid chain (often a fatty acid) to extend half-life and enable albumin binding. Tirzepatide (C20 diacid) and semaglutide (C18 diacid) are lipopeptides; the lipid tail is why they support weekly dosing.

A higher dose used at the start of a protocol to reach therapeutic levels faster than ongoing dosing would.

Also: lyophilised · lyophilization · freeze-dried · freeze dried

Freeze-dried, water removed under vacuum to produce a dry powder that's stable for shipment and storage.

The ongoing dose used after a loading or titration phase to sustain the therapeutic effect.

Also: mass spec · mass-spec

An analytical technique that measures the molecular mass of a compound, confirms the peptide's identity by matching its observed mass to the expected mass.

A signaling fragment generated by enzymatic cleavage of extracellular matrix proteins (collagen, elastin). Matrikines like GHK and GHK-Cu activate fibroblast transcription, driving the ~4,000-gene response that gives copper-peptide cosmetics their effect.

Also: melanocortin-1 receptor

Melanocortin-1 receptor, selectively expressed on melanocytes. Activation drives eumelanin (the tan-producing form of melanin) without the sexual-arousal effects mediated by MC4R. Melanotan I and afamelanotide are MC1R-selective; Melanotan II hits MC1R and MC4R together.

Also: Melanocortin-4 Receptor · Melanocortin 4 Receptor

Melanocortin-4 receptor, the brain GPCR responsible for appetite control and pigmentation, targeted by setmelanotide, bremelanotide (PT-141), and the melanotan series.

Also: microgram · micrograms · µg · ug

Microgram, one millionth of a gram, or one thousandth of a milligram.

Also: melanocortins · melanocortin system

A family of peptide hormones (α-MSH, ACTH, β-MSH) acting on five receptors (MC1R–MC5R) covering pigmentation, energy balance, and stress response.

Also: melanogenic

The biochemical synthesis of melanin pigment by melanocytes. Stimulated by α-MSH and the melanotan analogs.

Also: milligram · milligrams

Milligram, one thousandth of a gram. The standard unit for most therapeutic peptide vials.

Also: microdosing · micro-dose

A dose well below the standard therapeutic range, used either to titrate up gently or to chase a sub-clinical effect.

Also: mimetics

A compound designed to mimic the action of a natural hormone or peptide at the same receptor.

Also: MDP

A peptide encoded within mitochondrial DNA (rather than the nuclear genome) and exported to act as a hormone-like signal. MOTS-c and Humanin are the two best-characterized MDPs, both have systemic effects on metabolism, inflammation, and cell survival.

Also: Ibutamoren · MK677

An orally active, non-peptide ghrelin-mimetic GHS, frequently grouped with peptide GHRPs because of its similar mechanism.

Pertaining to the moist linings of the gut, airways, and other internal cavities. BPC-157, KPV, and the Khavinson bronchial/intestinal bioregulators all target mucosal repair and barrier integrity.

Also: myogenesis

Relating to the formation and differentiation of muscle cells. Myogenic activation of satellite cells is the cellular basis of hypertrophy and repair.

Also: myostatins · GDF-8

A muscle-suppressing growth factor (GDF-8) that caps skeletal-muscle hypertrophy; antagonized by follistatin and the central target of muscle-anabolic peptide research.

The amino end of a peptide chain. Tesamorelin's potency comes from a trans-3-hexenoyl modification on its N-terminus; Argireline mimics the N-terminus of SNAP-25.

Also: n-of-1 · n of 1 · N of 1

A single-person experiment, useful for individual decision-making, statistically meaningless for population claims.

Also: Non-Alcoholic Fatty Liver Disease · MASLD · MAFLD

Non-alcoholic fatty liver disease (recently re-classified as MASLD), a metabolic condition improved in trials of retatrutide, tirzepatide, and other multi-incretin agonists.

The most common side effect of GLP-1 receptor agonists, especially during dose escalation; usually transient and managed by slow titration. Tirzepatide's GIP component appears to attenuate the GLP-1 nausea curve in head-to-head data.

Also: gauge

The diameter of a needle, counter-intuitively, larger numbers mean thinner needles. Insulin syringes are 29G–31G.

When a hormone's downstream product loops back and suppresses further release of the original hormone.

Birth of new neurons in the adult brain, primarily in the hippocampus, the region central to memory and mood. P21, PE-22-28, and Cerebrolysin all claim to promote neurogenesis as a downstream effect of BDNF/NGF upregulation or growth-factor signaling.

A peptide that acts as a signal between neurons or between neurons and glia, often modulating mood, pain, appetite, or stress responses. VIP, DSIP, Semax, Selank, and the enkephalins are all neuropeptides or their analogs.

Also: neuroprotection

An effect that preserves neuron survival or function under injurious conditions (ischemia, oxidative stress, excitotoxicity).

Also: neurotrophins · neurotrophic factor · neurotrophic factors

A family of growth factors (BDNF, NGF, GDNF, NT-3) that support neuron survival, growth, and plasticity; mimicked or upregulated by nootropic peptides.

Also: nicotinamide n-methyltransferase

Nicotinamide N-methyltransferase, an enzyme that drains the NAD+ precursor pool and the SAM methyl-donor pool by methylating nicotinamide. 5-Amino-1MQ is a small-molecule NNMT inhibitor under preclinical study for metabolic and anti-obesity effects.

A drug or peptide intended to enhance cognition (memory, focus, learning). Semax, Selank, Cerebrolysin, and Dihexa are the peptide nootropics most discussed on the site; community usage is broader than published evidence supports.

Use of an FDA-approved drug for an indication or population the label doesn't cover, legal for licensed prescribers, but supported only by the literature, not the label.

Also: opioids · mu-opioid

Endogenous (enkephalins, endorphins, dermorphin) or synthetic compounds that bind mu-, delta-, or kappa-opioid receptors to modulate pain, mood, and reward. Dermorphin is an exceptionally potent mu-opioid peptide (~30-40x morphine); enkephalin-like activity contributes to Selank's anti-anxiety effects.

Swallowed and absorbed through the gut, typically very low bioavailability for peptides.

Also: appetite-stimulating

Appetite-stimulating. A characteristic side effect of ghrelin-mimetic peptides (GHRPs, hexarelin, MK-677), which is desirable for cachexia or wasting and undesirable for weight-loss goals.

Also: reactive oxygen species · ROS · oxidative damage

An imbalance between reactive oxygen species and the body's antioxidant defenses; a major driver of aging, neurodegeneration, and metabolic disease.

Also: beta cell · beta cells · β-cell · β-cells · pancreatic beta-cell

The insulin-producing cell of the pancreatic islets, the primary downstream target of incretins.

Inflammation of the pancreas, a labeled adverse event for every approved GLP-1 receptor agonist and a contraindication to restart. Risk appears low at standard doses but is the dominant gating factor for stacking two GLP-1s.

A molecule that activates a receptor only weakly, never reaching the full response of a full agonist.

Also: Cmax

The highest blood concentration during a dosing interval, typically reached shortly after each dose.

A peptide of exactly 15 amino acids, most often used to refer to BPC-157.

Also: peptides

A short chain of amino acids, typically 2 to 50, joined by peptide bonds. Smaller than a protein, larger than a single amino acid.

The covalent amide bond linking the carboxyl group of one amino acid to the amino group of the next.

Also: PD

What the drug does to the body, receptor binding, downstream signaling, and the resulting clinical effect.

Also: PK

What the body does to a drug, absorption, distribution, metabolism, and excretion.

Skin protection against UV-induced DNA damage and sunburn, clinically what eumelanin (the tan pigment driven by MC1R agonists) accomplishes. Afamelanotide (Melanotan I / Scenesse) is FDA/EMA-approved for photoprotection in erythropoietic protoporphyria patients.

The skin's production and distribution of melanin. Tanning peptides (Melanotan I, Melanotan II, afamelanotide) drive pigmentation by activating melanocortin receptors on melanocytes.

Also: pin

Community slang for self-injecting, short for 'pinning' a needle.

Also: anterior pituitary · pituitary gland

The pea-sized gland at the base of the brain that releases growth hormone, ACTH, TSH, LH, FSH, and prolactin.

Evidence stage prior to human trials, cell culture, animal models, and pharmacokinetic work in test animals. 'Preclinical only' on this site means there is no published human Phase 1+ data, only animal or in-vitro studies.

A pituitary hormone tied to lactation, sexual refractory period, and mood. Some GHRPs (GHRP-2, GHRP-6, hexarelin) cause a small prolactin rise alongside the GH pulse; Ipamorelin is preferred because it does not.

Cells dividing and increasing in number. Theoretical proliferation concerns drive the cancer-history contraindication for BPC-157, TB-500, IGF-1 analogs, and Follistatin.

Hormone release in discrete bursts rather than a steady drip, preserved by secretagogues but bypassed by recombinant hormones.

Also: receptors

A protein on or inside a cell that detects a specific signaling molecule and triggers a response.

Short-term loss of receptor response after sustained activation, even before the receptor is removed.

Also: reconstitute · reconstituting

Mixing lyophilized peptide powder with diluent (usually bacteriostatic water) to produce an injectable solution.

Also: research chemicals

A compound sold for laboratory or research use, not for human consumption, the label most non-FDA-approved peptides ship under.

Also: sarcopenic

Age-related loss of skeletal-muscle mass and strength; a primary therapeutic target for GH secretagogues, IGF-1 analogs, and myostatin inhibitors.

Also: satellite cell · satellite-cell activation

Quiescent muscle stem cells that activate after mechanical strain or IGF-1 signaling and fuse into existing fibers to grow or repair muscle.

The sensation of fullness that ends a meal, the central effect that drives GLP-1 weight loss.

Also: secretagogues

A compound that triggers the release of a hormone the body already makes.

Community shorthand for semaglutide.

Also: cellular senescence · senescent cell

Permanently growth-arrested cells that accumulate with age, secrete inflammatory factors (SASP), and drive age-related dysfunction; targets of senolytic therapies.

Also: senolytics

A drug or compound that selectively triggers apoptosis in senescent cells, clearing them without harming healthy tissue.

The order of amino acids in a peptide, written N-terminus to C-terminus and abbreviated by single letters.

A neurotransmitter governing mood, sleep, appetite, and gut motility. Semax modulates serotonergic systems; tesofensine inhibits serotonin reuptake; Selank engages serotonergic and GABAergic circuits.

Also: cell signaling · signal transduction

The cascade of receptor activation, second messengers, and gene expression triggered by a hormone or peptide binding its target. Different peptides hit different layers, receptor-level (GLP-1R, MC1R), kinase-level (AMPK, PI3K/Akt), or transcription-level (matrikine, Khavinson short peptides).

Also: small molecules · small-molecules

A low-molecular-weight (typically under 900 daltons) synthetic compound that is not a peptide or protein. Often orally bioavailable, unlike peptides.

A synaptic protein essential for neurotransmitter release at the neuromuscular junction. Argireline is an N-terminal SNAP-25 mimic that competes for the protein complex, locally relaxing facial muscles, botulinum toxin acts on the same target by cleaving SNAP-25.

A hypothalamic peptide that inhibits HGH release, the brake to GHRH's accelerator.

How long a peptide remains intact and active under given storage conditions, temperature, light, and reconstituted-vs-lyophilized state all matter.

Also: stacks · stacking · stacked

Two or more peptides used together as a coordinated protocol, typically to reach an effect neither could deliver alone.

Also: Css · plateau

The blood-level plateau a recurring-dose protocol reaches after enough doses that what's eliminated between doses equals what's added.

Pure water for injection without preservatives, used for single-dose preparations or short-cycle reconstitutions.

The peptide's chemical architecture, sequence, modifications (acetylation, fatty-acid conjugation, cyclization), and counter-ion form.

Also: SC · subcut · sub-q · sub-cut

Injected just below the skin into the fatty layer, the most common route for peptides.

The molecule an enzyme acts on. NAD+ is the substrate for sirtuin and PARP enzymes, which is why NAD precursors are explored for redox-cycle and DNA-repair support.

Also: synaptogenic

The formation of new synaptic connections between neurons, the cellular basis of learning. Promoted by BDNF, neurotrophin-mimetic peptides, and dendritic-spine modulators.

Acting throughout the body via the bloodstream, in contrast to local (acting only at the site of administration). Topical GHK-Cu serums have minimal systemic exposure; injected Follistatin-315 is intentionally systemic.

A class of white blood cell that orchestrates adaptive immunity. Thymosin Alpha-1 enhances T-cell maturation and is approved as Zadaxin for chronic hepatitis B/C in ~30 countries.

A rapid drop-off in drug effect after only a few doses, receptors become unresponsive faster than they can be replaced.

Also: telomere

The enzyme that extends telomeres (chromosome end-caps), counteracting the shortening that occurs with each cell division. Implicated in cellular aging and cancer.

Also: trifluoroacetate · trifluoroacetic acid

Trifluoroacetate counter-ion left over from peptide synthesis, a quality-control concern because TFA is mildly toxic and harder to remove.

Also: TGF-beta · Transforming Growth Factor Beta · TGFβ

A large signaling-protein superfamily (including activin, myostatin, BMPs) that regulates cell growth, differentiation, fibrosis, and immune balance.

Also: thrombotic · blood clot

The pathological formation of a blood clot inside a vessel; a known cardiovascular risk factor flagged in some anabolic-peptide safety discussions.

Also: thymic peptides · thymosin

Peptides derived from or modeled on thymus-gland proteins, includes Thymosin α1 (immune modulation) and Thymosin β4 / TB-500 (tissue repair).

Also: tides

Suffix shared by GLP-1 family drugs (semaglutide, tirzepatide, liraglutide, dulaglutide), used colloquially to refer to the class.

Also: tirzy

Community shorthand for tirzepatide.

Acting selectively on one cell type or organ, rather than broadly across the body. The Khavinson short-peptide bioregulators (Cartalax→cartilage, Testagen→testis, Pinealon→pineal) are characterized by tissue-specific gene-expression effects.

Also: titrate · titrating

Gradually increasing the dose over weeks to let the body adapt before reaching the target dose.

Applied to the skin, used for cosmetic peptides like copper peptides, palmitoyl pentapeptides, and matrixyl variants.

Also: gene transcription

The first step of gene expression, DNA is copied to messenger RNA, which is then translated into protein. Matrikine peptides (GHK, GHK-Cu) and Khavinson bioregulators act primarily by modulating transcription factors and gene-expression programs rather than by binding cell-surface receptors.

Also: TREK1 · K2P channel

A two-pore-domain potassium channel whose inhibition enhances serotonergic signaling, the proposed antidepressant mechanism of PE-22-28.

Also: Cmin

The lowest blood concentration during a dosing interval, measured just before the next dose.

Also: U100 · insulin syringe · U-100

An insulin syringe scaled so that 100 units = 1 mL. Widely referenced in the subcutaneous dosing literature.

When the cell increases the number of receptors at the surface, amplifying response to the natural signal.

Also: Vascular Endothelial Growth Factor

Vascular endothelial growth factor, the master signal for blood-vessel formation; VEGFR2 is its main receptor on endothelial cells.

Also: VEGF receptor 2

Vascular endothelial growth factor receptor 2, the principal receptor driving the formation of new blood vessels (angiogenesis). BPC-157's tissue-repair effect goes through VEGFR2 upregulation.

The small glass container, typically with a rubber stopper and aluminum crimp, that ships the lyophilized peptide.

Also: visceral adiposity · visceral abdominal fat

Metabolically active fat surrounding the abdominal organs (versus subcutaneous fat under the skin). Preferentially reduced by tesamorelin and high-dose GLP-1/GIP/glucagon agonists.

Also: World Anti-Doping Agency · WADA-banned

World Anti-Doping Agency, the international body whose Prohibited List bans most growth-hormone, IGF-1, and HGH-secretagogue peptides in tested sport.

A drug-free interval long enough for the previous compound to fully clear before starting another.