200 short, neutral definitions of the terms that recur across this site. Wherever one of these terms appears in a peptide, comparison, or question page, it links back to its entry here. These definitions are for general educational context only and do not replace professional medical judgment or formal clinical references.
The signalling molecules, receptors, and metabolic measures that recur across the incretin, growth-hormone, and metabolic sections of this site.
The cell-surface receptor through which myostatin and related TGF-β family ligands signal to limit muscle growth. Decoy receptors and antibodies aimed at it are the main pharmacological route to myostatin inhibition.
Related peptides: ACE-031, Follistatin 344, GDF-8 (Myostatin)
A cellular energy sensor that switches on when the ratio of AMP to ATP rises, shifting the cell toward glucose uptake and fat oxidation. It is the proposed mechanism behind several metabolic research compounds.
Related peptides: AICAR, MOTS-c, 5-amino-1mq
Related class pages: Metabolic and mitochondrial compounds
A hormone co-secreted with insulin by pancreatic beta cells. It slows gastric emptying and promotes satiety, and long-acting amylin analogs are studied for appetite and body weight.
Related peptides: Cagrilintide, Cagrilintide + Semaglutide
The growth of new blood vessels from existing ones. It is central to wound healing and is the mechanism most often proposed for healing peptides in animal models.
Related peptides: BPC-157, TB-500 (Thymosin Beta-4 fragment)
Related class pages: Healing and anti-inflammatory peptides
Programmed cell death — an orderly self-destruct sequence a cell runs when it is damaged or no longer needed, in contrast to the messy, inflammatory death of necrosis.
A protein that supports the survival of existing neurons and the growth of new synapses. It is the most commonly cited mechanism for nootropic peptide claims, usually measured in rodents.
Related peptides: Semax, Selank, Cerebrolysin, Dihexa
Related class pages: Neuro, nootropic, and cosmetic peptides
The pressure of blood against artery walls, reported as systolic over diastolic in mmHg. It is a common secondary endpoint in metabolic trials because weight change tends to move it.
The tight layer of cells lining brain capillaries that keeps most large or charged molecules out of the brain. Whether a peptide crosses it is often the deciding question for any claimed central effect.
How body weight divides between fat mass and fat-free mass. Two interventions can produce identical weight change with very different composition outcomes, which is why trials increasingly report it separately.
Weight in kilograms divided by height in metres squared. It is a population-level screening measure, widely used to set trial eligibility, and it does not distinguish fat from muscle in an individual.
Related tools: BMI calculator
A broad term for the combined risk of conditions such as type 2 diabetes, cardiovascular disease, and related metabolic disturbances.
A large, long trial designed to measure hard events — cardiovascular death, heart attack, stroke — rather than laboratory markers. Regulators require these for many metabolic drugs, and they are the strongest evidence a compound on this site can have.
The most abundant structural protein in skin, tendon, and bone. Cosmetic peptide claims usually rest on measured changes in collagen synthesis by fibroblasts rather than on clinical outcomes.
The body’s primary stress hormone, released by the adrenal glands; certain growth hormone secretagogues can transiently increase it.
A small signalling protein that immune and other cells use to communicate. Pro-inflammatory cytokines such as TNF-α and IL-6 are the usual readout in anti-inflammatory peptide studies.
Related class pages: Healing and anti-inflammatory peptides
The total calories the body uses in a day, made up of resting metabolism, the cost of digesting food, and physical activity. Glucagon-receptor activity is one of the few peptide mechanisms proposed to raise it directly.
The main estrogen in the reproductive years, produced largely by the ovaries and by conversion from testosterone in fat and other tissues.
The scaffold of collagen, elastin, and other molecules that cells sit in and attach to. Remodelling it is how tissue repairs itself, and how skin loses or regains firmness.
Blood glucose measured after an overnight fast, typically at least eight hours without food. It is one of the standard measures used to diagnose and monitor diabetes.
The connective-tissue cell that produces collagen and the rest of the extracellular matrix. Most cosmetic and healing peptide research is measured by what fibroblasts do in culture.
A pituitary gonadotropin that drives ovarian follicle development in women and supports sperm production in men.
Related peptides: HMG
The rate at which food leaves the stomach and enters the small intestine. GLP-1 and amylin signalling slow it, which blunts post-meal glucose spikes and prolongs fullness — and also explains much of the nausea seen with these drugs.
Related class pages: GLP-1 receptor agonists and related incretin therapies
A stomach-derived “hunger hormone” that stimulates appetite and, by acting on the growth hormone secretagogue receptor, promotes growth hormone release. Several research peptides mimic it.
Related peptides: GHRP-2, GHRP-6, Ipamorelin, Hexarelin
The growth hormone secretagogue receptor, GHS-R1a — the target of ghrelin and of the GHRP family of growth hormone secretagogues. Activating it triggers a growth hormone pulse and, depending on the compound, appetite signalling.
Related peptides: GHRP-2, GHRP-6, Ipamorelin, MK-677 (Ibutamoren)
An incretin hormone that, together with GLP-1, can enhance glucose-dependent insulin secretion and is a target for certain dual and triple agonist peptides.
Related peptides: Tirzepatide, Retatrutide
Related class pages: GLP-1 receptor agonists and related incretin therapies
A hormone released from cells in the small intestine after a meal. It increases insulin release when glucose is high, suppresses glucagon, slows how fast the stomach empties, and signals fullness in the brain — which is why drugs that imitate it affect both blood sugar and appetite.
Related peptides: Semaglutide, Liraglutide, Tirzepatide
Related class pages: GLP-1 receptor agonists and related incretin therapies
A receptor found on cells in the pancreas, brain, and other tissues that responds to the hormone GLP-1 and helps regulate insulin secretion, glucagon, gastric emptying, and appetite signals.
Related peptides: Semaglutide, Tirzepatide, Retatrutide
Related class pages: GLP-1 receptor agonists and related incretin therapies
A medicine that activates glucagon-like peptide-1 (GLP-1) receptors, typically used and studied for effects on blood glucose, appetite, and body weight.
Related peptides: Semaglutide, Liraglutide, Dulaglutide
Related class pages: GLP-1 receptor agonists and related incretin therapies
A pancreatic hormone that raises blood glucose and can increase energy expenditure. Newer dual and triple agonist peptides add glucagon-receptor activity to their incretin effects.
Related peptides: Retatrutide, Survodutide, Mazdutide
How closely blood glucose is kept within a target range over time, usually summarised by HbA1c together with fasting and post-meal glucose readings.
A hypothalamic hormone released in pulses that tells the pituitary to secrete luteinizing hormone and follicle-stimulating hormone. Continuous, non-pulsatile stimulation of its receptor has the opposite effect and suppresses those hormones.
Related peptides: Gonadorelin, Triptorelin Acetate, KissPeptin-10
A pituitary hormone released in pulses that influences growth, body composition, and metabolism. Most of its longer-term effects are mediated indirectly through IGF-1 produced in the liver.
Related peptides: HGH 191AA (Somatropin), Sermorelin Acetate, MK-677 (Ibutamoren)
Related class pages: Growth hormone and growth factors
A peptide or other compound that stimulates the body’s own release of growth hormone, often by acting on the growth hormone secretagogue receptor rather than supplying growth hormone directly.
Related peptides: Ipamorelin, GHRP-2, GHRP-6, Hexarelin, CJC-1295 + Ipamorelin
Related class pages: Growth hormone and growth factors
A synthetic peptide modeled on natural GHRH that acts at the pituitary to stimulate physiologic, pulsatile growth hormone release.
Related peptides: Sermorelin Acetate, CJC-1295 with DAC, CJC-1295 without DAC, Tesamorelin
Related class pages: Growth hormone and growth factors
A blood test that reflects average blood glucose over roughly the preceding 2–3 months. It is the standard primary endpoint in diabetes trials.
The brain region that links the nervous system to the endocrine system, releasing hormones such as GHRH, GnRH, and somatostatin that in turn control the pituitary. It also carries much of the appetite circuitry that incretin drugs act on.
A group of hormones, including GLP-1 and GIP, that are released from the gut after eating and help regulate insulin secretion and blood glucose in a glucose-dependent way.
Related class pages: GLP-1 receptor agonists and related incretin therapies
The state in which muscle, liver, and fat respond poorly to insulin, so the pancreas must secrete more to keep glucose in range. It underlies type 2 diabetes and much of the metabolic syndrome.
How strongly tissues respond to a given amount of insulin. Higher sensitivity means less insulin is needed to move glucose out of the blood.
A hormone produced mainly by the liver in response to growth hormone that helps mediate many of GH’s effects on growth, metabolism, and body composition. Serum IGF-1 is the usual laboratory proxy for growth hormone exposure.
Related peptides: HGH 191AA (Somatropin), Tesamorelin, IGF-1 LR3
Related class pages: Growth hormone and growth factors
Everything in the body that is not fat — muscle, bone, organs, and water. Substantial weight loss from any cause usually includes some lean mass, which is why trials report it alongside total weight.
The metabolic breakdown of stored fat (triglycerides) into fatty acids, often discussed as a target for fat-loss compounds.
Related peptides: AOD-9604, HGH Fragment 176-191
A pituitary gonadotropin that triggers ovulation in women and stimulates testosterone production by the testicular Leydig cells in men.
Related peptides: HCG, Gonadorelin, HMG
Metabolic dysfunction-associated steatohepatitis, previously called non-alcoholic steatohepatitis: fatty liver accompanied by inflammation and liver-cell injury, which can progress to fibrosis and cirrhosis. The naming changed in 2023; older papers use NASH.
A family of receptors (such as MC1R and MC4R) and signaling peptides involved in skin pigmentation, appetite, and sexual function.
A cluster of findings — central obesity, raised blood pressure, raised triglycerides, low HDL cholesterol, and raised fasting glucose — that together predict cardiovascular disease and type 2 diabetes.
The process by which cells build new mitochondria, increasing their capacity to produce energy aerobically. Endurance exercise is its best-established trigger.
A small peptide encoded within mitochondrial DNA (such as MOTS-c or humanin) that acts as a signaling molecule in metabolism and cellular stress responses.
A protein secreted by muscle that acts as a brake on muscle growth. Blocking it increases muscle mass in animals, which is why myostatin inhibitors are a recurring — and so far clinically unsuccessful — drug target.
Related peptides: GDF-8 (Myostatin), Follistatin 344, ACE-031
The formation of new neurons. In adult mammals it is largely confined to a few brain regions, and its extent in adult humans remains debated.
Related class pages: Neuro, nootropic, and cosmetic peptides
A short-lived gas signalling molecule that relaxes vascular smooth muscle, widening blood vessels. It is the pathway PDE5 inhibitors act on, and it is distinct from the central mechanism of melanocortin agonists.
A chronic condition defined in most guidelines and trials by a body mass index of 30 kg/m² or above, or 27 and above with a weight-related complication. Trial eligibility criteria on this site are usually stated in those terms.
Related tools: BMI calculator
An imbalance in which reactive oxygen species outpace the cell’s antioxidant defences, damaging lipids, proteins, and DNA. Mitochondria are both a major source and a major target.
Related peptides: SS-31, Glutathione
The insulin-producing cell of the pancreatic islets. Beta cells also release amylin, and their progressive loss of function is a defining feature of type 2 diabetes.
A pea-sized gland at the base of the brain that releases growth hormone, gonadotropins, and other hormones on instructions from the hypothalamus. Most secretagogue and releasing-hormone peptides act here.
After a meal. Postprandial glucose is the rise in blood sugar following eating, and it is the window in which incretin hormones do most of their work.
A pituitary hormone best known for its role in lactation; some growth hormone secretagogues can modestly raise it as a side effect.
A family of locally acting lipid signalling molecules derived from arachidonic acid, involved in inflammation, pain, smooth-muscle tone, and blood flow. Prostaglandin E1 is the active moiety of alprostadil.
Related peptides: Alprostadil
Hormone secretion that occurs in bursts rather than continuously. Growth hormone is naturally released in pulses, which secretagogue strategies aim to preserve.
The primary receptor for the hormone relaxin, found in heart, kidney, and vascular tissue, where its activation is associated with vasodilation and reduced fibrosis.
Related peptides: B7-33
The sense of fullness that ends a meal and delays the next one. Appetite-acting peptides are usually described as increasing satiety rather than suppressing hunger outright.
A compound designed to selectively clear senescent cells — cells that have stopped dividing but persist and secrete inflammatory signals. It is an active area of aging research with limited human data.
Related peptides: FOXO4
A family of NAD-dependent enzymes that modify proteins involved in metabolism, DNA repair, and stress responses. They are the usual mechanistic hook for NAD-precursor and longevity claims.
Voluntary muscle attached to bone. It is also the body’s largest site of insulin-stimulated glucose disposal, which is why muscle mass matters metabolically and not only functionally.
A hypothalamic hormone that brakes growth hormone release, acting as the counterweight to GHRH. The interplay between the two is what makes natural growth hormone secretion pulsatile.
The repetitive DNA cap at the end of a chromosome that shortens with each cell division. Telomere length is a popular but contested biomarker of biological aging.
Related peptides: Epitalon
Dense collagen structures that connect muscle to bone (tendon) and bone to bone (ligament). Both are poorly vascularised, which is why they heal slowly and why healing-peptide research targets them.
Related peptides: BPC-157, TB-500 (Thymosin Beta-4 fragment)
Related class pages: Healing and anti-inflammatory peptides
The principal androgen, produced mainly in the testes and in smaller amounts by the ovaries and adrenal glands. Several peptides discussed on this site influence it indirectly by acting on the pituitary–gonadal axis.
Related peptides: HCG, Gonadorelin, KissPeptin-10
The main form in which fat is stored and transported in blood. Raised fasting triglycerides are one component of the metabolic syndrome.
A chronic condition in which insulin resistance and declining beta-cell output leave blood glucose persistently elevated. It is the original approved indication for most GLP-1 receptor agonists.
Related class pages: GLP-1 receptor agonists and related incretin therapies
Fat that accumulates deep inside the abdomen around internal organs, often linked to cardiometabolic risk more strongly than fat just under the skin.
Related peptides: Tesamorelin, Semaglutide, Tirzepatide
The staged repair process — clotting, inflammation, new tissue formation, then remodelling — that follows tissue injury. Animal wound-healing models are the dominant evidence base for the healing peptides on this site.
Related class pages: Healing and anti-inflammatory peptides
How a compound behaves in the body — absorption, duration, receptor activity — and the vocabulary used to describe how it is given.
Attaching a fatty-acid chain to a peptide so that it binds reversibly to albumin in the blood. The bound fraction acts as a circulating reservoir, slowing clearance and extending half-life from hours to days.
Related peptides: Semaglutide, Liraglutide
A molecule that binds a receptor and switches it on, producing the same kind of response as the body’s own signal. A partial agonist activates the receptor less fully than the natural one.
A molecule that occupies a receptor without activating it, blocking the natural signal from binding. The effect is to suppress a pathway rather than to stimulate it.
Total drug exposure over time, calculated as the area under a plot of blood concentration against time. It is the standard way to compare how much drug two regimens actually deliver.
How tightly a molecule sticks to its receptor, usually reported as Kd or Ki — lower numbers mean tighter binding. High affinity does not by itself mean a strong effect; that also depends on how well the bound molecule activates the receptor.
The fraction of an administered dose that reaches the bloodstream intact. Intravenous dosing is 100% by definition; peptides taken by mouth are usually far lower because digestive enzymes break them down.
The rate at which the body removes a drug from the blood, usually by the kidneys, the liver, or enzymatic breakdown in plasma. Together with distribution volume it determines half-life.
A reservoir of drug that sits at the injection site and releases slowly into the circulation, stretching out the duration of action.
A planned stepwise increase in dose over weeks, used in labels to reduce gastrointestinal side effects and in phase 1 trials to find the highest tolerated dose.
How the size of an effect changes as the dose changes. A clean dose–response is one of the stronger signals that an observed effect is real rather than noise.
An enzyme that inactivates native GLP-1 and GIP within minutes of their release. Long-acting incretin drugs are engineered to resist it, which is what turns a minutes-long hormone into a weekly medicine.
Related class pages: GLP-1 receptor agonists and related incretin therapies
A change in one drug’s effect caused by another drug, food, or supplement. Compounds that slow gastric emptying can alter how quickly other oral medicines are absorbed.
The concentration of a compound that produces half of its maximum effect in a given assay. It is a potency measure and only comparable between compounds tested in the same system.
The breakdown of a peptide by enzymes in blood and tissue that cut it at specific points in its chain. Resisting it is the main design problem in turning a natural peptide into a usable drug.
The breakdown a swallowed drug undergoes in the gut wall and liver before it reaches the general circulation. It is a main reason most peptides are injected rather than taken orally.
The time it takes for the amount of a substance in the body to fall by half. It sets how often a compound must be dosed and roughly how long it takes to clear — about four to five half-lives to be substantially eliminated.
Related reference tables: Peptide half-lives
Related tools: Half-life plotter
The tendency of an injected peptide or protein to provoke an antibody response. Anti-drug antibodies can reduce a drug’s effect or, less often, cause reactions, so trials report them routinely.
An injection into muscle tissue, which is better perfused than subcutaneous fat and so generally gives faster absorption.
A larger initial dose used to reach the target concentration faster than repeated maintenance doses would. It shortens the wait for steady state but does not change the eventual level.
The dose a regimen settles at once titration is complete, intended to hold the effect steady over time.
Attaching polyethylene glycol chains to a peptide or protein. The added bulk slows kidney filtration and enzymatic attack, lengthening how long the molecule circulates.
Related peptides: PEG-MGF
What a drug does to the body — the relationship between concentration at the target and the resulting biological effect. The counterpart to pharmacokinetics.
What the body does to a drug: absorption, distribution, metabolism, and excretion. It is the source of half-life, peak concentration, and dosing-interval figures.
How much of a compound is needed to produce a given effect. A more potent drug works at a lower dose; that says nothing about whether its maximum effect is larger.
A protein that a signalling molecule binds to in order to produce an effect inside a cell. Which receptors a peptide binds, and how tightly, determines nearly everything about what it does.
The process by which continuous or repeated stimulation makes a receptor less responsive, often by internalising it or reducing how many are expressed on the cell surface.
The degree to which a compound acts on its intended receptor rather than on related ones. Selectivity is what separates, for example, a GHRP that raises growth hormone alone from one that also moves cortisol and prolactin.
The point in repeated dosing at which the amount going in equals the amount being cleared, so peak and trough levels stop rising. It takes roughly four to five half-lives to reach.
Related tools: Half-life plotter
An injection into the fat layer just under the skin, from which a drug is absorbed relatively slowly into the bloodstream. It is the usual route for the injectable peptides described on this site.
Related tools: Syringe simulator
A rapidly diminishing response to a compound with repeated dosing, so the same dose produces progressively smaller effects over a short period.
Adjusting a dose in steps, usually upward from a low starting dose, to find a level that works while limiting side effects. Approved incretin labels specify fixed escalation schedules for this reason.
Study designs, statistics, and publication terms used when this site describes what a piece of research does and does not show.
Withholding treatment allocation from participants, investigators, or outcome assessors. Blinding often fails in practice when a drug has obvious effects such as nausea or visible weight loss.
A published description of one patient, or of a handful, with no control group. Useful for flagging a rare harm or an unexpected observation; not evidence that a treatment works.
The US National Library of Medicine’s public registry of clinical studies. Each record carries an NCT identifier, and comparing the registered protocol with the published paper is how outcome switching gets caught.
A systematic review published by Cochrane, an international network with strict methodology and conflict-of-interest rules. Cochrane reviews are generally treated as among the more rigorous syntheses available.
A range of values compatible with the data at a stated level of confidence, usually 95%. A wide interval signals an imprecise estimate, however impressive the central number looks.
A design in which each participant receives both treatments in sequence, separated by a washout period, so each person acts as their own control. It needs fewer participants but only suits stable, reversible conditions.
A design in which neither participants nor investigators know who is receiving the active treatment, so expectations cannot bias reported symptoms or outcome assessment.
How large a difference a treatment produced, expressed in real units or as a standardised measure. It is the question that matters clinically once significance is established.
A precise statement of what a trial is measuring, including how events such as stopping treatment are handled. Two estimands on the same dataset — effect while taking the drug versus effect regardless of adherence — can give visibly different numbers.
This site’s four-level label for how much human evidence a compound has: approved medicine, clinical-stage, preclinical, or minimal evidence. It appears on every peptide page.
Related reference tables: Peptide evidence tiers
A notice attached to a published paper when a journal has credible doubts about its integrity but has not concluded an investigation. It is a warning short of retraction.
The ratio of the rate at which an event occurs in the treatment group to the rate in the control group over time. Below 1 favours treatment; a ratio whose confidence interval crosses 1 has not shown a difference.
In glassware — an experiment in cells or isolated tissue outside a living organism. Concentrations used in vitro are often unreachable in a living body, which limits what such results predict.
In a living organism, whether animal or human. In-vivo results account for absorption, metabolism, and clearance in a way cell studies cannot.
Analysing every participant in the group they were randomised to, whether or not they completed treatment. It preserves randomisation and usually gives a more conservative estimate than analysing completers only.
Under study but not approved for sale as a medicine. In the United States an investigational drug is given to people under an Investigational New Drug application filed with the FDA.
Related reference tables: Peptide evidence tiers
A statistical combination of results from multiple studies into a single pooled estimate. Its reliability is capped by the quality of the studies it pools and by which studies got published in the first place.
Research that records what happens without assigning treatment — cohort and case-control designs. It can show association at scale but cannot rule out that the groups differed to begin with.
A study in which everyone knows who is getting what. Open-label extensions follow participants after a blinded trial ends and give long-term safety data, but their efficacy figures are not placebo-controlled.
Evaluation of a manuscript by independent researchers before a journal publishes it. It filters out some errors; it does not verify that the underlying data exist or are correct.
The FDA describes phase 1 as safety and dosing in roughly 20–100 volunteers, phase 2 as efficacy and side effects in up to several hundred patients, and phase 3 as pivotal efficacy and safety studies in roughly 300–3,000 participants. Phase 4 studies run after approval.
A small preliminary study run to test feasibility and gather effect estimates for designing a larger trial. Pilot results are routinely over-read as findings in their own right.
An inactive treatment made to look like the real one, given to a comparison group. Placebo groups often improve, which is precisely why an uncontrolled result cannot be read as evidence of effect.
A trial design in which the comparison group receives a placebo rather than nothing or another active drug, isolating the drug’s own contribution to any change.
Research done before any human dosing — cell-culture and animal work. Most peptides on this site have preclinical evidence only, and effects in rodents translate to humans far less often than they fail to.
Related reference tables: Peptide evidence tiers
The single outcome a trial is designed and powered to answer, chosen before the data are collected. Secondary endpoints are informative but are not the basis on which the trial succeeds or fails.
The US National Library of Medicine’s free index of biomedical literature, covering more than 30 million citations. Every study reference on this site is expected to resolve to a PubMed, PMC, or DOI record.
A study in which participants are assigned to treatments by chance, so that known and unknown differences between groups even out. It is the strongest single-study design for showing that a treatment caused an outcome.
A journal’s formal withdrawal of a published paper because of error or misconduct. Retracted papers keep accumulating citations for years afterward, so a claim can remain in circulation long after its source was withdrawn.
The number of participants in a study, usually written as n. Small samples produce unstable estimates and are the single most common reason an early positive result does not replicate.
A conclusion that a result is unlikely to have arisen by chance alone under the null hypothesis, conventionally at p < 0.05. It says nothing about whether the effect is large enough to matter.
A review that follows a pre-specified search and appraisal protocol so the selection of studies is reproducible, rather than chosen at the author’s discretion.
Approval pathways, labelling, compounding, and the legal categories that determine how a substance may be marketed in a given country.
An FDA pathway allowing earlier approval of drugs for serious conditions with unmet need on the basis of a surrogate endpoint thought to predict clinical benefit. Sponsors must still run confirmatory trials, and the FDA has procedures to withdraw the drug if benefit is not confirmed.
A biological product shown to be highly similar to an already-approved reference biologic with no clinically meaningful differences. Unlike a small-molecule generic it is not an identical copy, because biologics cannot be manufactured identically.
The most serious warning the FDA can require on a drug label, set apart in a box at the top, used for risks that can lead to death or serious injury. Its presence is a fact about the label, not a judgment about an individual’s risk.
The active pharmaceutical ingredient used as a starting material in compounding. Under section 503A it may only be used if it meets an applicable USP or NF monograph, is a component of an FDA-approved drug, or appears on the FDA’s 503A bulks list — and it must arrive with a valid certificate of analysis from an FDA-registered manufacturer.
The preparation of a customised medicine by combining or altering ingredients, done by a licensed pharmacy or outsourcing facility. Compounded drugs are not FDA-approved and are not reviewed for safety, effectiveness, or quality before they are sold.
The US National Library of Medicine’s public database of current FDA drug labelling. It is where the prescribing information cited on this site is retrieved from.
A US regulatory category for products intended to supplement the diet, which are not reviewed for safety or effectiveness before sale. Peptide drugs that have been investigated as drugs are generally excluded from this category.
The European Union agency that evaluates medicines for the EU market. Its scientific opinions lead to marketing authorisations granted by the European Commission, so approval status can differ from the FDA’s.
A determination by the US Food and Drug Administration that a drug’s benefits outweigh its risks for a specific labelled use, based on submitted evidence. Approval is always for particular indications, not for a substance in general.
Related reference tables: FDA-approved peptides
A published FDA notice telling a company that the agency believes it has violated the law, and requiring a response. Warning letters are public and searchable, which makes them useful primary evidence about a supplier.
Supply that moves outside a manufacturer’s or regulator’s intended channel — sold legally somewhere, but not through the route a regulated medicine would take. Chain of custody, storage, and identity are unverifiable by the buyer.
The specific condition or population a medicine is approved to treat, as written in its labelling. A drug can be approved for one indication and merely investigational for another.
A legal or regulatory region, such as a country or state, that may have its own rules about how therapies can be approved, marketed, and used.
China’s National Medical Products Administration, the regulator that approves medicines for the Chinese market. Several metabolic peptides have been approved there on the basis of trials conducted in Chinese populations.
Prescribing an approved drug for an indication, dose, or population not covered by its approved labelling. It is lawful medical practice in many jurisdictions, but it means the labelled evidence does not cover that use.
A status granted to a drug intended for a rare disease, carrying development incentives such as a period of market exclusivity. Designation is not approval and does not by itself mean the drug works.
The FDA-approved label for a drug, covering its indications, dosing, contraindications, and warnings. It is the authoritative source for what a medicine is actually approved to do.
A label applied to material sold for laboratory work rather than human or veterinary use. It is a marketing category, not a quality certification, and it carries no requirement that the contents be sterile, pure, or accurately identified.
The section of the US Federal Food, Drug, and Cosmetic Act that exempts drugs compounded by a licensed pharmacist or physician from pre-market approval, CGMP, and certain labelling requirements — provided conditions are met, including that compounding follows receipt of a valid patient-specific prescription.
The FD&C Act section, added by the 2013 Drug Quality and Security Act, creating a voluntary category of compounders called outsourcing facilities. Unlike 503A pharmacies they must follow CGMP, are inspected by the FDA on a risk-based schedule, report adverse events, and may supply without a patient-specific prescription.
A non-governmental body that publishes public quality standards — monographs — for drug substances and preparations. US law makes compliance with an applicable USP monograph a condition for several compounding pathways.
World Anti-Doping Code vocabulary. Many peptides on this site are prohibited in sport regardless of their regulatory status as medicines.
The formal term for a laboratory report identifying a prohibited substance or its markers in an athlete’s sample. It starts a results-management process; it is not by itself a finding of a rule violation.
A longitudinal record of an athlete’s own blood and steroid markers, used to detect doping indirectly by flagging changes from that individual’s baseline rather than by detecting a substance.
Samples collected around a competition versus at any other time, including unannounced. Substances prohibited only in competition can be used out of competition; those prohibited at all times cannot.
An anti-doping rule violation established without a positive test — for example possession, trafficking, refusing a test, or evidence from an investigation. Several high-profile peptide cases have been decided this way.
WADA’s annually updated list of substances and methods banned in sport, organised into numbered classes. Some are prohibited at all times, others only in competition.
Related reference tables: WADA-prohibited peptides
The Prohibited List class covering any pharmacological substance not currently approved by any governmental regulatory health authority for human therapeutic use. It is a catch-all that captures most purely experimental research peptides.
Related reference tables: WADA-prohibited peptides
The Prohibited List class covering peptide hormones, growth factors, related substances, and mimetics — including growth hormone, its releasing factors and secretagogues, IGF-1 and its analogs, and erythropoietin-receptor agonists. Prohibited at all times, in and out of competition.
Related reference tables: WADA-prohibited peptides
The Prohibited List class covering hormone and metabolic modulators, including myostatin-pathway inhibitors and metabolic modulators such as AMPK activators and PPARδ agonists. Prohibited at all times.
Related reference tables: WADA-prohibited peptides
A Prohibited List category for substances more likely to have been consumed for a non-doping purpose, allowing greater flexibility in sanctioning. Peptide hormones in S2 are non-specified, so the default first-violation sanction is more severe.
Advance permission for an athlete to use a prohibited substance for a documented medical condition, granted by an anti-doping organisation against published criteria. It must normally be obtained before use, not claimed after a positive test.
The body that publishes the World Anti-Doping Code and the annual Prohibited List adopted by Olympic sports and most national anti-doping organisations. Its rules are independent of whether a substance is an approved medicine.
Related reference tables: WADA-prohibited peptides
Structure, identity, and the analytical measures used to describe what is actually in a vial.
The form most synthetic peptides are supplied in, where acetate counter-ions balance the peptide’s charge. Acetate contributes to the powder’s weight, so net peptide content is lower than the gross mass unless stated otherwise.
The building block of peptides and proteins. Twenty standard amino acids are used to build human proteins, and swapping even one in a peptide chain can change its stability or receptor activity substantially.
The order of amino acids in a peptide, conventionally written from the N-terminus to the C-terminus using one- or three-letter codes. It is the peptide’s identity — two products with different sequences are different substances whatever they are named.
A molecule deliberately modified from a natural one — a substituted amino acid, an added fatty acid, a shortened chain — to change its stability, potency, or duration while keeping the same target.
Sterile water containing a small amount of benzyl alcohol as a preservative, which inhibits bacterial growth and so allows a vial to be entered more than once. It differs from plain sterile water, which has no preservative.
Related peptides: BAC water
A unique identifier assigned by the Chemical Abstracts Service to a specific chemical substance. It pins down identity in a way that trade names and abbreviations do not.
A document reporting the analytical results for a specific batch — identity, purity, and any other tested attributes. Its value depends entirely on who performed the testing and whether the batch number matches the material in hand.
How much substance is dissolved per unit of liquid, for peptides usually written in mg/mL. It follows entirely from the vial contents and the volume of liquid added at reconstitution, so the same vial can be made into many different concentrations.
Related tools: Peptide reconstitution calculator, Unit converter
Lipopolysaccharide from the outer membrane of Gram-negative bacteria. It survives ordinary sterilisation, is not removed by sterile filtration alone, and can cause fever and inflammatory reactions if injected.
Any ingredient in a formulation other than the active substance — bulking agents, buffers, preservatives, stabilisers. Excipients affect stability and tolerability and are listed on approved labels.
A small syringe graduated in insulin units rather than millilitres, where 100 units correspond to 1 mL on a U-100 syringe. The unit markings are a volume scale, not a dose of any particular peptide.
Related tools: Syringe simulator, Unit converter
Freeze-dried into a stable powder by removing water under vacuum from a frozen solution. Most research peptides ship lyophilized and must be reconstituted with a liquid before use.
An analytical method that measures a molecule’s mass-to-charge ratio, used to confirm that a peptide’s observed mass matches its expected sequence. Paired with liquid chromatography it is the standard identity and purity test.
The mass of one molecule, given in daltons or g/mol. For peptides it follows directly from the sequence, so a stated molecular weight that does not match the stated sequence is a red flag.
The chemical link joining one amino acid to the next, formed between a carboxyl group and an amino group with the loss of water. A chain of these bonds is what makes a molecule a peptide.
A short section of a larger peptide or protein, studied on the assumption it carries part of the parent molecule’s activity. A fragment does not necessarily reproduce the parent’s effects.
Related peptides: HGH Fragment 176-191, AOD-9604
The proportion of a sample that is the intended peptide, usually measured chromatographically and quoted as a percentage. Purity says nothing about identity, sterility, or endotoxin content — those are separate tests.
Dissolving a freeze-dried (lyophilized) peptide in a sterile liquid, such as bacteriostatic water, so it can be measured and used. The volume added sets the concentration and therefore how much liquid corresponds to a given dose.
Related peptides: BAC water
Related tools: Peptide reconstitution calculator
The absence of viable microorganisms in a preparation. Sterility is a property of a validated process and its container, and it is independent of chemical purity.
Names that simply state how many amino acids a peptide contains — three, five, and fifteen respectively. The prefix is descriptive and says nothing about what the peptide does.
The small sealed glass container a peptide is supplied in. A single-dose vial is intended to be entered once and discarded; a multi-dose vial contains a preservative so it can be entered repeatedly.
Related tools: Peptide reconstitution calculator
Terms used in label warnings, trial safety tables, and adverse-event reporting.
Any unfavourable medical occurrence in someone receiving a treatment, whether or not it was caused by that treatment. Trials record all of them, which is why adverse-event tables also list events in the placebo group.
Compression of the median nerve at the wrist causing numbness, tingling, and weakness in the hand. It is a recognised dose-related effect of growth hormone, thought to follow from fluid retention in the carpal tunnel.
A situation stated on a drug’s label in which it should not be used because the risk clearly outweighs any benefit. Contraindications are absolute; warnings and precautions are the weaker category.
Fluid retention in tissue, typically noticed as swelling of the hands, ankles, or feet. It is a characteristic dose-related effect of growth hormone and, less markedly, of some secretagogues.
Gallstones and gallbladder inflammation, which occur more often with rapid weight loss from any cause and appear in the labelling of several incretin drugs.
Nausea, vomiting, diarrhoea, and constipation — the dominant adverse-event category for incretin-based drugs, driven largely by slowed gastric emptying and generally most pronounced during dose escalation.
Related class pages: GLP-1 receptor agonists and related incretin therapies
Blood glucose low enough to cause symptoms such as shakiness, sweating, or confusion. Incretin drugs rarely cause it alone because their insulin effect is glucose-dependent, but risk rises when they are combined with insulin or sulfonylureas.
Local redness, itching, swelling, or a lump at the point of injection. Usually transient and self-limiting, and one of the most commonly reported events for injected peptides.
A rare thyroid cancer arising from the calcitonin-producing C cells. Rodent studies with GLP-1 receptor agonists showed C-cell tumours, which is the basis of the boxed warning and the contraindication in people with a personal or family history of MTC or MEN 2.
A potentially serious complication of some fertility treatments in which the ovaries become enlarged and fluid shifts can cause abdominal discomfort and other systemic symptoms.
Inflammation of the pancreas, typically presenting as severe upper abdominal pain. It appears in the warnings sections of incretin drug labels as an uncommon but serious event.
An adverse event that results in death, is life-threatening, requires or prolongs hospitalisation, causes lasting disability, or a congenital anomaly. The definition is regulatory and does not mean simply severe.