Reference

Peptides and metabolic health glossary

Plain-English UK definitions for terms used across PeptideClear. Marked up with DefinedTermSet schema for AI search. 125 terms.

GLP-1: Glucagon-Like Peptide-1. A hormone the gut releases after eating. GLP-1 medications mimic this hormone to slow gastric emptying, increase insulin sensitivity, and reduce appetite.
GIP: Glucose-dependent Insulinotropic Polypeptide. A second gut hormone. Mounjaro is a dual GIP and GLP-1 agonist. Wegovy is GLP-1 only.
Tirzepatide: The active molecule in Mounjaro. A weekly injection developed by Eli Lilly. Approved in the UK for type 2 diabetes (2022) and weight management (2024).
Semaglutide: The active molecule in Wegovy and Ozempic. A weekly injection developed by Novo Nordisk. Wegovy is the weight-management licensed product in the UK; Ozempic is the diabetes brand of the same molecule at lower doses.
NICE TA1026: NICE Technology Appraisal 1026. The 2024 NICE guidance on tirzepatide for managing overweight and obesity. Defines the BMI thresholds, comorbidity requirements, and ethnicity-adjusted thresholds for NHS access.
Cohort 1, 2, 3: The phased rollout of NHS England Mounjaro access. Cohort 1 (BMI 40+, 4+ comorbidities) live since June 2025. Cohort 2 launches 23 June 2026. Cohort 3 expected April 2027.
NHS Cohort 1: BMI 40+ (37.5+ ethnicity-adjusted), 4 or more weight-related comorbidities. Live since June 2025.
NHS Cohort 2: BMI 35+ (32.5+ ethnicity-adjusted), 3 or more comorbidities. Launches 23 June 2026.
NHS Cohort 3: BMI 30+ (27.5+ ethnicity-adjusted), 2 or more comorbidities. Expected April 2027.
ICB: Integrated Care Board. The 42 NHS England regional bodies that commission services in their area. Mounjaro rollout pace varies by ICB.
QOF: Quality and Outcomes Framework. NHS England primary-care contract framework. April 2026 update added GLP-1-relevant indicators.
Aftercare: Maintenance phase after reaching goal weight on a GLP-1. 82% regain at least 25% of lost weight within 12 months of stopping (Oxford analysis, January 2026).
High-touch route: Private clinic with app, coach, monthly check-in. Numan, Voy, Manual, Juniper. £200 to £300 per month.
Low-touch route: Online pharmacy with questionnaire then ship. Phlo, Pharmacy2U, SimplyMeds, Boots Online Doctor, Asda Online Doctor. £150 to £200 per month.
Maintenance dose: A continued lower or steady GLP-1 dose at goal weight, intended to prevent regain rather than drive further loss. Some clinics offer this; pharmacy-direct routes typically do not.
GLP-1 face: Colloquial term for facial volume loss after rapid weight loss on GLP-1. Mechanism is normal facial fat reduction; effect is more pronounced after age 35 because skin elasticity has declined.
SURMOUNT-1: The pivotal Eli Lilly tirzepatide trial. 72 weeks, average 22% weight loss at maximum dose.
STEP-1: The pivotal Novo Nordisk semaglutide trial. 68 weeks, average 15% weight loss at maximum dose.
SELECT: The Wegovy cardiovascular outcomes trial. Showed 20% reduction in major cardiovascular events. Underpins the April 2026 UK CV indication.
GHK-Cu: Glycyl-histidyl-lysine bound to copper. The most studied cosmetic peptide. Discovered by Pickart 1973. Used in serums for collagen support, barrier repair, skin firming.
Matrixyl 3000: A branded blend by Sederma combining palmitoyl tripeptide-1 and palmitoyl tetrapeptide-7. Most commercially recognised cosmetic peptide complex.
Argireline: Acetyl hexapeptide-8. Cosmetic peptide marketed for fine line reduction by inhibiting muscle contraction at the skin surface. Topical only.
INCI: International Nomenclature of Cosmetic Ingredients. The standardised ingredient list on every cosmetic product. Ingredient position correlates loosely with concentration.
Palmitoyl tripeptide-1: A signal peptide. One of the two peptides in Matrixyl 3000. Stimulates collagen and glycosaminoglycan synthesis in skin.
Palmitoyl tetrapeptide-7: A signal peptide. The second peptide in Matrixyl 3000. Reduces inflammation by limiting interleukin-6 production.
Snail mucin: Snail secretion filtrate. K-beauty staple, often paired with peptides. Hydrating and barrier-supportive.
Hydrolysed collagen: Collagen broken down (typically by enzymes) into smaller peptides for better gut absorption. Most marketed at 3 to 6 kDa molecular weight.
Type I collagen: The main collagen type in skin, hair, nails, tendons, and bone. Marine collagen is mostly Type I. Bovine collagen is Type I and III combined.
Type II collagen: The main collagen type in cartilage. Sourced from chicken sternum. Dosed in milligrams (40 mg undenatured / UC-II) not grams. Different absorption profile from Type I.
Type III collagen: The collagen type in skin elasticity, gut lining, and blood vessels. Almost always present alongside Type I in bovine collagen.
UC-II: Undenatured Type II collagen. The form retained from chicken cartilage that preserves immune-modulating activity. Used at 40 mg/day for joint support.
Marine collagen: Collagen sourced from fish skin and scales. Almost entirely Type I. Smallest molecular weight typically (1 to 3 kDa). Strong absorption.
Bovine collagen: Collagen sourced from cow hide. Type I + III combined. Most affordable per gram. Standard for skin and gut goals.
Vegan collagen: Misnomer. No plant supplement contains collagen. "Vegan collagen" products contain amino acid precursors (lysine, proline, glycine) plus vitamin C and assume your body builds collagen from them.
kDa: Kilodalton. Unit of molecular weight. Hydrolysed collagen at 3 to 6 kDa is small enough for efficient gut absorption.
Bolke 2019: Industry-funded RCT showing skin elasticity improvement with 10 g/day hydrolysed collagen over 90 days. Among the trials supporting collagen efficacy.
Choi 2019: Systematic review of 11 collagen RCTs concluding short-term effects on skin elasticity and hydration. Industry funding declared in source studies.
Shaw 2017: RCT showing 15 g hydrolysed collagen + 50 mg vitamin C, 60 minutes pre-exercise, doubled collagen synthesis at the tendon. The protocol behind tendon-recovery dosing.
BPC-157: Body Protection Compound 157. Synthetic peptide derived from a protein found in human gastric juice. Animal data only, no human RCTs. Sold under "research use only" framing in the UK.
TB-500: Synthetic fragment of thymosin beta-4. Research peptide with rodent data on tissue repair and anti-inflammatory effects. No published human RCTs. UK regulatory status same as BPC-157.
MOTS-c: Mitochondrial Open Reading frame of the Twelve S rRNA-c. Mitochondrial-derived peptide with mouse data on metabolic regulation and late-life intervention.
Ipamorelin: Growth-hormone secretagogue developed by Novo Nordisk. Phase II discontinued for postoperative ileus. No marketing authorisation. Research use only in the UK.
Tesamorelin: Growth-hormone-releasing-hormone analogue. The only peptide on this list with an FDA approval (HIV-associated lipodystrophy, EGRIFTA WR). Not NHS-prescribed. Research use only via UK retailers.
CoA: Certificate of Analysis. Document from a third-party lab confirming purity and identity of a chemical sample. Not a sterility certificate. Not a biological-activity certificate.
HPLC: High-Performance Liquid Chromatography. Lab technique that separates the components of a sample by chemical property. Used to measure peptide purity. Does not prove biological activity.
Mass spectrometry: Lab technique that identifies a molecule by its mass-to-charge ratio. Used alongside HPLC to confirm the named peptide is what is in the vial. Stronger than HPLC alone.
Research use only: The UK regulatory framing under which research peptides are sold. Products are marketed without health claims, not for human or animal consumption, sitting outside the medicines regulatory tier.
WADA: World Anti-Doping Agency. Maintains the prohibited list for tested athletes. Several research peptides (BPC-157, TB-500, MOTS-c, ipamorelin) are on it.
GPhC: General Pharmaceutical Council. The UK regulator of pharmacies and pharmacists. A legitimate UK online pharmacy holds a GPhC registration number.
POM: Prescription Only Medicine. Cannot be sold or dispensed without a prescription from a qualified prescriber. All GLP-1 weight management medications in the UK are POM.
MHRA: Medicines and Healthcare products Regulatory Agency. UK medicines regulator. Issues marketing authorisations and enforces against unlicensed medicinal products.
MHRA Yellow Card: The UK system for reporting adverse drug reactions. Anyone can submit a report at yellowcard.mhra.gov.uk.
ASA: Advertising Standards Authority. UK regulator of advertising. Issued enforcement notice on consumer-facing GLP-1 advertising in September 2025.
CAP code: Committee of Advertising Practice code. The set of rules ASA enforces. Restricts advertising of POM products to the public.
PIL: Patient Information Leaflet. The leaflet inside every UK medication box. The authoritative source on dosing, side effects, and missed-dose advice.
BNF: British National Formulary. The UK reference for prescribers on medicines, doses, and indications. Authoritative on every licensed UK medicine.
Medicines Act 1968: The primary UK statute governing the sale and supply of medicines. Sets the framework for what counts as a medicinal product.
Human Medicines Regulations 2012: The implementing regulations under the Medicines Act 1968. Day-to-day rules on UK medicines, including advertising, supply, and licensing.
Misuse of Drugs Act 1971: Controls drugs of abuse in the UK. Most research peptides are NOT controlled under this act.
Psychoactive Substances Act 2016: Bans novel psychoactive substances. Research peptides are NOT scheduled under this act.
Ethnicity-adjusted BMI: NICE-recommended BMI threshold reduction of 2.5 kg/m² for South Asian, Chinese, Black African, and African-Caribbean populations, reflecting higher metabolic risk at lower BMI.
Comorbidity: A weight-related health condition that counts toward NICE TA1026 eligibility. Includes type 2 diabetes, hypertension, dyslipidaemia, sleep apnoea, cardiovascular disease.
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Mounjaro KwikPen: Eli Lilly's multi-dose pre-filled pen device for tirzepatide. UK rollout from 2024. Replaces single-use vials with a 4-dose pen.
Dose titration: The structured ramp-up from starting dose to maintenance dose. Mounjaro typically titrates monthly: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg.
Stopping rule (NHS): NICE TA1026 continuation criterion. Patients must achieve at least 5 percent weight loss from baseline by month 6 for NHS Mounjaro to continue.
Plateau: Period of stalled weight loss on a GLP-1 despite continued use at the same dose. Common at 9 to 12 months. Prescriber options: hold, titrate, or maintenance pivot.
Cohort: Phased rollout group in the NHS Mounjaro plan. Cohort 1 (BMI 40+, 4+ comorbidities) live since June 2025. Cohort 2 June 2026. Cohort 3 April 2027.
TA875: NICE Technology Appraisal 875. The 2022 NHS approval of tirzepatide for type 2 diabetes (the separate pathway from weight management TA1026).
TA664: NICE Technology Appraisal 664. The 2017 NHS approval of liraglutide (Saxenda) for weight management. Largely superseded by Mounjaro and Wegovy in 2024 to 2025 prescribing.
SmPC: Summary of Product Characteristics. The detailed prescriber-facing document on a UK licensed medicine. Authoritative on indication, dosing, contraindications, side effects.
SELECT trial: The Novo Nordisk semaglutide cardiovascular outcomes trial. 17,604 participants over 5 years. 20% reduction in major cardiovascular events. Underpins April 2026 UK CV indication.
SURMOUNT-4: Eli Lilly tirzepatide trial on weight maintenance after initial loss. Demonstrated continued use maintains loss; discontinuation drives regain.
REDEFINE: Novo Nordisk semaglutide trial published December 2025. Compared higher-dose semaglutide outcomes.
STEP-3: Novo Nordisk semaglutide trial with intensive behavioural therapy added to medication. Demonstrated additive effect of structured coaching alongside the drug.
C-cell hyperplasia: Thyroid C-cell proliferation observed in rodent studies with GLP-1 agonists. Drives the boxed warning against use in patients with personal or family history of medullary thyroid carcinoma or MEN 2.
Gastroparesis: Delayed gastric emptying. Already a feature of how GLP-1 medications work; can become clinically problematic at higher doses or in susceptible patients.
Compounded GLP-1: Custom-mixed semaglutide or tirzepatide from non-licensed sources. Common in the US through 2024. Not legal for routine UK supply. MHRA enforcement focus.
Bariatric pathway: The NHS surgical route (gastric sleeve, gastric bypass) for severe obesity. GLP-1 access (NICE TA1026) does not exclude future bariatric referral.
Specialist Weight Management Service (SWMS): NHS tier-3 service providing multi-disciplinary support for severe obesity. The commissioning route through which NHS Mounjaro is delivered in most ICBs.
Acetyl tetrapeptide-9: A cosmetic peptide marketed in some UK serums for collagen-supportive effect. Less commercially recognised than Matrixyl 3000 or GHK-Cu.
Acetyl octapeptide-3: Marketed as SNAP-8. Cosmetic peptide positioned as a longer-chain Argireline alternative.
Acetyl dipeptide-3 aminohexanoate: Marketed in some lash-growth serums under "peptide" claims. Disputed efficacy.
Stratum corneum: The outermost skin layer (15 to 20 cells thick). The barrier topical peptides must cross to reach the dermis.
Transepidermal water loss (TEWL): Rate of water loss through skin. A common skin-barrier integrity measure in cosmetic trials.
Fibroblast: Dermal cell that produces collagen and extracellular matrix. The target cell type for topical peptide signalling.
Elastin: Skin protein responsible for elastic recoil. Decline with age contributes to skin laxity. Topical peptides have mixed evidence for elastin synthesis.
Glycosaminoglycan (GAG): Long unbranched polysaccharide. Includes hyaluronic acid. Component of skin extracellular matrix that peptides can upregulate.
Niacinamide: Vitamin B3. The cosmetic peptide stack-mate that is most reliably compatible across formulations and pH.
Peptide-retinoid stacking: Using a peptide serum and a retinoid (retinol, retinaldehyde, tretinoin) in the same routine. Time-separated (peptide AM, retinoid PM) is the standard approach.
Peptide-vitamin C stacking: Using a peptide serum (especially copper peptide) and L-ascorbic acid vitamin C in the same step. Generally avoided: low-pH vitamin C destabilises copper peptide.
Glycine: The smallest amino acid. Roughly one-third of every collagen molecule. The amino acid the body needs more of than diet typically provides.
Proline: Cyclic amino acid. Roughly 15 percent of collagen. Provides structural rigidity to the triple helix.
Hydroxyproline: Modified proline. Vitamin C-dependent. The marker amino acid used to quantify collagen in tissue and blood.
Lysine: Essential amino acid. Combines with proline to form the crosslinks in mature collagen fibres.
Crowley 2009: RCT in osteoarthritis patients showing UC-II 40 mg/day outperformed glucosamine + chondroitin on joint function over 90 days.
Lugo 2016: RCT in active adults with knee pain showing UC-II 40 mg/day improved knee comfort during exercise.
Cult Beauty: UK premium beauty retailer. Major UK distribution channel for collagen and cosmetic peptide brands.
LookFantastic: UK beauty retailer. Major UK distribution for global collagen brands including Vital Proteins.
Holland and Barrett: UK high-street health retailer. Mid-tier collagen and supplement distribution.
Beauty Pie: UK members-only beauty subscription. Houses own-brand peptide products at member-only pricing.
GHRP: Growth Hormone Releasing Peptide. Class of synthetic peptides (Ipamorelin, GHRP-2, GHRP-6, hexarelin) that act at the ghrelin receptor.
GHRH: Growth Hormone Releasing Hormone. Endogenous hypothalamic 44-amino-acid hormone. Synthetic analogues include Sermorelin, Tesamorelin, CJC-1295.
GHSR-1a: Growth Hormone Secretagogue Receptor type 1a. The ghrelin receptor at which GHRPs (Ipamorelin, hexarelin) act.
DAC linker: Drug Affinity Complex linker. The chemical group attached to CJC-1295 that binds albumin and extends half-life from 30 minutes to 8+ days.
EGRIFTA: US brand name for tesamorelin. FDA-approved for HIV-associated lipodystrophy. The only UK-relevant peptide on this list with any major-market marketing authorisation.
Sikiric group: Research group at the University of Zagreb led by Predrag Sikiric. Origin of most BPC-157 preclinical literature from 2003 onwards.
Thymosin beta-4: Naturally occurring 43-amino-acid peptide present in most mammalian cells. TB-500 is a synthetic fragment.
Mitochondrial-derived peptide: Short peptides encoded by mitochondrial DNA rather than nuclear DNA. MOTS-c is the best-studied. Class of putative metabolic regulators.
mTOR: Mammalian target of rapamycin. Cellular pathway central to growth and longevity research. Some peptides modulate it indirectly.
AMPK: AMP-activated protein kinase. Cellular energy sensor. Activated by MOTS-c and other metabolic peptides in preclinical models.
Lyophilised: Freeze-dried. The standard delivery form for research peptides in glass vials. Stable at room temperature for short periods.
Bacteriostatic water: Sterile water with 0.9 percent benzyl alcohol added. Used for reconstituting research peptides because the benzyl alcohol suppresses microbial growth in the vial.
UKAD: UK Anti-Doping. The national anti-doping organisation. Enforces WADA prohibited list across UK competitive sport.
GMC: General Medical Council. UK regulator of doctors. Every prescriber at a UK GLP-1 clinic holds a GMC registration.
CQC: Care Quality Commission. Regulator of UK health and social care services. Most UK longevity clinics are CQC-registered for the clinical interpretation component.
FSA: Food Standards Agency. Regulator of UK food supplements (including collagen and vitamins). Distinct from MHRA.
EAMS: Early Access to Medicines Scheme. MHRA route for unlicensed medicines to reach UK patients pre-approval. Not used for any current GLP-1.
Named-patient supply: UK route for prescribing an unlicensed medicine to a specific named patient. Outside the scope of routine GLP-1 supply.
Unlicensed medicinal product: A medicine without UK MHRA marketing authorisation. Includes any GLP-1 imported from outside the UK supply chain. MHRA enforcement target.
Specials: UK term for unlicensed medicines manufactured specifically for a UK patient by a registered specials manufacturer. Distinct from imported unlicensed.
Off-label: Use of a licensed medicine outside its UK MHRA indication. Legal when prescriber-initiated and clinically justified. Common for some GLP-1 uses.

Peptides and metabolic health glossary

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