PeptideReport.ai Reference

Peptide Glossary

Name: Peptide Glossary
Creator: Dr. Scott DelBoccio, DMD
Published: 2026-09-13

Every field guards its gates with vocabulary. This glossary defines the 65 terms used across PeptideReport.ai — from peptide bond to CONSORT compliance to the gray market — so you can read a compound profile, a clinical trial, or a vendor's marketing copy and know exactly what is being claimed. Definitions describe what words mean; they are not instructions for use.

Written and reviewed by Dr. Scott DelBoccio, DMD·Last reviewed September 13, 2026·65 terms in 6 sections·How evidence levels are assigned

Peptide Fundamentals

14 terms

The core vocabulary of peptide chemistry and pharmacology — what these molecules are and how their properties are described.

Peptide: A short chain of amino acids linked by peptide bonds, generally smaller than a protein (conventionally fewer than about fifty amino acids). Peptides act as signaling molecules throughout the body — hormones, neurotransmitter modulators, and immune messengers are all peptides. Most compounds profiled on PeptideReport.ai are synthetic peptides designed to mimic or modify these natural signals.
Amino Acid: One of the twenty standard organic building blocks from which peptides and proteins are assembled. The identity and order of amino acids in a chain determine the molecule's shape and biological activity. Some therapeutic peptides also incorporate modified or non-standard amino acids to resist enzymatic breakdown.
Peptide Bond: The chemical bond — an amide linkage — that joins the carboxyl group of one amino acid to the amino group of the next, forming the backbone of every peptide and protein. Enzymes called peptidases break these bonds, which is one reason unmodified peptides tend to have short half-lives in the body.
Sequence: The specific order of amino acids in a peptide, conventionally written from the N-terminus to the C-terminus. Sequence is a peptide's identity: changing even one position can alter potency, receptor selectivity, or stability. Published sequences are what allow independent laboratories to verify that a compound is what it claims to be.
Analog: A synthetic peptide whose sequence has been deliberately modified from a natural template to change its properties — most often to extend half-life or sharpen receptor selectivity. Semaglutide, for example, is an analog of the natural hormone GLP-1, engineered to remain active for days rather than minutes.
Fragment: A peptide consisting of only a portion of a larger parent protein's sequence, retaining some of the parent's biological activity. TB-500 corresponds to the active fragment of the protein thymosin beta-4, and AOD-9604 is a fragment of human growth hormone studied for isolated metabolic effects.
Lyophilization: Freeze-drying: a preservation process that removes water from a peptide solution under vacuum, leaving a stable powder. Most pharmacy-supplied and research peptides are shipped lyophilized, because the dry form resists chemical degradation far longer than a liquid solution does.
Reconstitution: The process of dissolving a lyophilized (freeze-dried) peptide powder in a sterile diluent to return it to liquid form before use. In legitimate clinical settings, reconstitution is performed by compounding pharmacies or under the supervision of the prescribing physician. PeptideReport.ai does not publish reconstitution instructions.
Half-Life: The time required for the concentration of a compound in the body to fall by half. Half-life determines how long a peptide's signal lasts: natural GHRH survives only minutes in circulation, while engineered analogs carrying protective modifications can act for hours or days. It is a descriptive pharmacokinetic property, not a dosing guide.
Bioavailability: The fraction of an administered compound that reaches systemic circulation intact. Peptides taken by mouth are largely digested before they can be absorbed, which is why most peptide therapeutics are administered by injection under medical care — and why marketing claims for “oral peptides” deserve scrutiny.
Mechanism of Action: The specific biochemical process through which a compound produces its effect — which receptor it binds, which pathway it activates or blocks. A plausible mechanism is where evidence begins, not where it ends: many compounds with elegant mechanisms have failed when tested in human trials.
Receptor: A protein, usually on a cell's surface, that recognizes a specific signaling molecule and triggers a response inside the cell. Peptides work by fitting receptors the way a key fits a lock, and the distribution of a receptor across tissues explains why a single peptide can affect several body systems at once.
Agonist & Antagonist: An agonist binds a receptor and activates it, mimicking the body's natural signal; an antagonist binds the same receptor without activating it, blocking the natural signal instead. Partial agonists activate a receptor at less than full strength. Most peptides covered on this site are agonists of their target receptors.
Endogenous vs. Synthetic: Endogenous means produced naturally within the body — endogenous growth hormone, endogenous GLP-1. Synthetic means manufactured in a laboratory. A synthetic peptide may be sequence-identical to its endogenous counterpart or deliberately modified as an analog; the distinction matters for regulation, drug testing, and immune reactions.

The Growth Hormone Axis

11 terms

The hypothalamus–pituitary signaling system behind an entire category of peptides, from Sermorelin to CJC-1295.

Growth Hormone (GH): A peptide hormone secreted by the pituitary gland in pulses — the largest during deep sleep — that drives tissue growth and repair, largely by way of IGF-1. Its secretion declines steadily with age. Prescription growth hormone is FDA-approved only for specific diagnosed deficiencies and conditions, not for anti-aging use.
IGF-1 (Insulin-Like Growth Factor 1): The hormone produced mainly by the liver in response to growth hormone; it mediates most of GH's growth and repair effects. Because blood IGF-1 stays relatively stable through the day while GH rises and falls in pulses, physicians measure IGF-1 as the standard laboratory marker of growth hormone axis activity.
GHRH (Growth Hormone–Releasing Hormone): The hypothalamic hormone that signals the pituitary to release growth hormone. Synthetic GHRH analogs — Sermorelin, CJC-1295, and the FDA-approved Tesamorelin — work by amplifying this natural release signal rather than by supplying growth hormone directly.
GHRP (Growth Hormone–Releasing Peptide): A family of synthetic peptides — Ipamorelin is the best-known — that stimulate growth hormone release through the ghrelin receptor, a separate pathway from GHRH. Because the two pathways are complementary, GHRPs and GHRH analogs are frequently studied in combination.
Secretagogue: Any substance that causes another substance to be secreted. In the peptide context, “growth hormone secretagogue” is the umbrella term covering both GHRH analogs and GHRPs — compounds that prompt the body's own pituitary to release growth hormone rather than replacing it from outside.
Ghrelin Mimetic: A compound that imitates ghrelin — the stomach-derived “hunger hormone” — at its receptor. Because that receptor also sits on the pituitary, ghrelin mimetics such as Ipamorelin trigger growth hormone release. Selectivity matters here: less selective mimetics also raise appetite and cortisol.
Pulsatile Secretion: The body's natural pattern of releasing certain hormones in discrete bursts rather than a steady stream. Growth hormone is strongly pulsatile, with the largest pulses during slow-wave sleep. Secretagogues that preserve this pulsing pattern are considered more physiologic than continuous exposure, which can desensitize the axis.
Somatopause: The gradual, age-related decline in growth hormone secretion and IGF-1 levels that begins in early adulthood. Somatopause is a normal feature of aging, not a disease — and whether reversing it produces a net benefit in healthy adults remains an open scientific question, a distinction this site treats as central.
Somatostatin: The hypothalamic hormone that inhibits growth hormone release — the brake to GHRH's accelerator. The alternation between somatostatin tone and GHRH tone is what creates growth hormone's pulsatile pattern, and somatostatin is a key reason secretagogue response varies from one person to the next.
Feedback Loop: The self-regulating circuit by which a hormone's downstream products suppress its further release. In the growth hormone axis, rising IGF-1 signals the hypothalamus and pituitary to cut GH output. Secretagogues remain subject to this feedback, which is often cited as a theoretical safety advantage over injected growth hormone itself.
DAC (Drug Affinity Complex): A chemical modification that binds a peptide reversibly to albumin, the most abundant blood protein, dramatically extending its half-life. CJC-1295 with DAC persists in circulation for roughly a week, versus roughly half an hour for the unmodified peptide — a design change that also flattens growth hormone's natural pulsatility.

Metabolic & Incretin Signaling

7 terms

The gut-hormone biology behind Semaglutide, Tirzepatide, and Retatrutide — the most rigorously validated corner of peptide medicine.

GLP-1 (Glucagon-Like Peptide-1): An incretin hormone released by the intestine after eating. It boosts insulin secretion, suppresses glucagon, slows stomach emptying, and reduces appetite. Synthetic GLP-1 receptor agonists such as Semaglutide are among the most thoroughly validated peptide drugs ever developed.
GIP (Glucose-Dependent Insulinotropic Polypeptide): The second major incretin hormone, which enhances insulin release and appears to influence fat metabolism. Long considered the lesser incretin, GIP became prominent when Tirzepatide — which targets both the GIP and GLP-1 receptors — outperformed GLP-1-only therapy in head-to-head trials.
Glucagon: The pancreatic hormone that raises blood sugar and increases energy expenditure — insulin's counterpart. Its receptor is the third target in triple agonist compounds such as Retatrutide, where a measure of glucagon activity is engineered in to raise calorie expenditure.
Incretin: The class of gut hormones — chiefly GLP-1 and GIP — released in response to food, which amplify insulin secretion in a glucose-dependent way. Because they act mainly when blood sugar is elevated, incretin-based drugs carry a low risk of hypoglycemia on their own.
GLP-1 Receptor Agonist: A drug that activates the GLP-1 receptor, reproducing and amplifying the body's natural incretin signal. The class includes several FDA-approved medications — Semaglutide among them — for type 2 diabetes and chronic weight management, and it anchors Level I on this site's evidence scale.
Dual / Triple Agonist: A single engineered peptide designed to activate two or three metabolic receptors at once. Tirzepatide is a dual GLP-1/GIP agonist; Retatrutide is a GLP-1/GIP/glucagon triple agonist. Combining signals in one molecule has produced the largest weight reductions yet recorded in pharmacotherapy trials.
Titration: The clinical practice of starting a medication low and adjusting it stepwise, under physician supervision, to balance effect against side effects. Incretin therapies are titrated over weeks to months, chiefly to manage gastrointestinal tolerability. Titration schedules are individualized prescribing decisions made by the treating physician — not published protocols to self-apply.

Evidence & Clinical Trials

14 terms

How claims get tested — and the exact definitions behind the Evidence Level badges (I, Ib, IIb, V) used on every compound profile.

Randomized Controlled Trial (RCT): The reference-standard experiment for testing whether a treatment works: participants are randomly assigned to receive either the treatment or a comparator (often placebo), ideally with neither participants nor investigators knowing who received which. Randomization is what separates causation from coincidence.
Placebo: An inert treatment, indistinguishable from the real one, given to a trial's control group. Placebo responses in subjective outcomes — energy, mood, recovery — are large and reliable, which is precisely why anecdotal reports about peptides cannot substitute for controlled data.
Clinical Trial Phases (I / II / III): The staged sequence of human drug testing. Phase I establishes safety and pharmacokinetics in small groups; Phase II probes efficacy and dose–response in patients; Phase III tests efficacy at scale against a comparator and is the usual basis for FDA approval. Many peptides discussed online never progress past Phase II — or never enter human trials at all.
Endpoint: The predefined outcome a clinical trial is designed to measure — the specific, quantified answer to the question “did it work?” Primary endpoints are declared before a trial begins; results discovered afterward in the data are hypothesis-generating, not proof.
Surrogate Marker: A measurable stand-in — a blood level, an imaging finding — used in place of the clinical outcome that actually matters. A rising IGF-1 level is a surrogate; feeling and functioning better is an outcome. Surrogates make trials faster, but they have repeatedly misled medicine when the stand-in and the real outcome diverge.
Evidence Level I: The top tier of PeptideReport.ai's evidence scale: the compound is FDA approved, or the use is supported by a Cochrane systematic review. Level I reflects both demonstrated efficacy and formal regulatory or systematic-review scrutiny of the underlying trial data.
Evidence Level Ib: The second tier of the site's evidence scale: the use is supported by a single CONSORT-compliant Western randomized controlled trial, but replication, systematic review, or regulatory approval is still lacking. Strong Phase III data awaiting completed regulatory review also sits at Ib.
Evidence Level IIb: The third tier of the site's evidence scale: the evidence comes from Phase I/II trials measuring surrogate markers, or from Russian and Eastern European Phase II/III trials whose designs or reporting fall short of CONSORT standards. Signals at this level are genuine but unconfirmed by Western-standard trials.
Evidence Level V: The lowest tier of the site's evidence scale: preclinical evidence only — cell culture and animal studies, with no human trial data of any kind. Most peptides sold as “research chemicals” sit at Level V, however compelling their laboratory results may appear.
CONSORT: The Consolidated Standards of Reporting Trials: an internationally adopted checklist specifying what a published randomized trial must disclose — randomization method, blinding, participant flow, prespecified outcomes. CONSORT compliance is this site's threshold for treating a trial as fully credible, and it is written into the Level Ib definition.
Cochrane Review: A systematic review produced under the Cochrane Collaboration's methodology, which locates every qualifying trial on a question, grades their quality, and pools the results. It is widely regarded as the most rigorous form of evidence synthesis in medicine, and a supportive Cochrane review qualifies a use for Level I on this site.
Preclinical: Research conducted before any human testing: biochemical assays, cell culture, and animal studies. Preclinical results establish plausibility, not efficacy — the large majority of compounds with promising preclinical data go on to fail when tested in humans.
In Vitro / In Vivo: In vitro (“in glass”) describes experiments performed in cell culture or test tubes; in vivo (“in the living”) describes experiments in living organisms, usually animals. Effects seen in vitro frequently vanish in vivo, and animal in vivo results frequently fail to translate to humans — each step down the chain weakens a claim.
Human Equivalent Dose (HED): An allometric calculation that converts a dose used in animal research into its approximate human counterpart, correcting for differences in body surface area and metabolic rate between species rather than scaling by weight alone. On this site, HED figures appear only as calculations that put animal studies in context — they are never recommendations.

Regulatory & Sourcing

10 terms

The legal landscape peptides actually occupy in the United States — approval, compounding, and the gray market, stated plainly.

FDA Approval: The U.S. Food and Drug Administration's formal determination, after review of manufacturing quality and clinical trial data, that a drug is safe and effective for a specific indication. Approval attaches to a use, a formulation, and a manufacturer — a peptide being “FDA approved” for one condition says nothing about unapproved uses or unregulated copies of the molecule.
Off-Label Use: A physician's prescription of an FDA-approved drug for a condition, population, or manner of use outside its approved labeling. Off-label prescribing is legal and common in medicine, but it shifts the evidentiary burden onto the prescribing physician, because the FDA has not vetted that particular use.
Orphan Drug Designation: An FDA status granted to compounds in development for rare diseases, carrying incentives such as extended market exclusivity. It is a development-stage designation, not an approval — marketing that leans on “orphan drug status” as evidence of efficacy is misleading.
Compounding Pharmacy (503A / 503B): A pharmacy that prepares customized medications outside mass manufacture. 503A facilities compound patient-specific prescriptions; 503B “outsourcing facilities” produce larger batches under stricter FDA oversight. Compounded peptides occupy a legitimate but shifting middle ground, and the FDA periodically revises which peptides may be compounded at all.
Research Chemical: A compound sold nominally for laboratory research, without pharmaceutical-grade manufacturing standards, purity verification, or regulatory oversight. Peptides sold this way carry no assurance of identity, sterility, or accurate labeling — independent testing has repeatedly found mislabeled and contaminated products in this channel.
“Research Use Only” (RUO): The label disclaimer under which gray-market peptides are typically sold, formally declaring that the product is not for human use. The label is a legal shield for the seller, not a safety standard for the buyer; a product purchased under an RUO label sits entirely outside medical and regulatory protection.
WADA Prohibited List: The World Anti-Doping Agency's annually updated list of substances banned in competitive sport. Growth hormone secretagogues, GHRPs, and most investigational peptides appear on it — meaning tested athletes can face sanctions over compounds that are otherwise legal to possess.
GRAS (Generally Recognized as Safe): An FDA category for food ingredients whose safety is established by expert consensus — a food-additive standard, not a drug standard. Some peptide marketing borrows the GRAS status of a related oral ingredient to imply that an injectable product is safe; the designation does not transfer.
IND (Investigational New Drug): The application a sponsor files with the FDA before beginning human trials of an unapproved compound. An active IND means a compound is being formally studied in humans under regulatory oversight — a meaningful signal of development seriousness that most gray-market peptides lack.
Gray Market: The unregulated commercial space where peptides are sold outside pharmaceutical supply chains — typically online, labeled “research use only,” without prescriptions, quality assurance, or accountability. Understanding that this market exists is part of regulatory literacy; PeptideReport.ai provides no sourcing information and links to no vendors.

Clinical & Physiological Terms

9 terms

Mechanism vocabulary that recurs across the compound profiles — the biology behind the claims.

Angiogenesis: The formation of new blood vessels from existing ones — essential to wound healing and tissue repair. Pro-angiogenic activity is central to the preclinical profiles of BPC-157 and TB-500, and it is also a reason unstudied long-term effects deserve caution: tumors depend on angiogenesis too.
Cytoprotection: The capacity of a compound to shield cells from injury — chemical, ischemic, or mechanical — rather than to repair damage after the fact. BPC-157's preclinical literature is built largely on cytoprotective findings in the gastrointestinal tract.
Neurotrophic: Promoting the growth, survival, or connectivity of neurons. Neurotrophic mechanisms are the basis of research interest in compounds such as Semax and Dihexa, which act on nerve-growth-factor pathways; human evidence for these effects remains far thinner than the mechanism literature.
Immunomodulation: The adjustment of immune system activity — up, down, or toward better regulation — as distinct from simple stimulation or suppression. Thymosin Alpha-1, approved in several countries as an immunomodulator, is the reference example in the peptide space.
Anxiolytic: Reducing anxiety. In peptide research the term appears chiefly in the Russian literature on Selank, which was developed as a non-sedating anxiolytic; the supporting trials sit at Level IIb on this site's evidence scale.
Nootropic: A substance claimed to enhance cognitive function — memory, focus, processing speed. The word is a marketing category, not a regulatory one; this site uses it descriptively for compounds such as Semax while grading the actual evidence separately.
Telomere / Telomerase: Telomeres are the protective caps on chromosome ends that shorten with each cell division; telomerase is the enzyme that can rebuild them. Epithalon's longevity claims rest on proposed telomerase activation — a mechanism with intriguing preclinical support and no confirmatory Western human trials.
Mitochondrial Biogenesis: The creation of new mitochondria within cells, expanding their capacity for energy production. It is the proposed mechanism behind research on MOTS-c and SS-31 in metabolism and age-related energy decline — work that remains largely at the preclinical and early-trial stage.
Melanocortin: A family of hormones and receptors governing pigmentation, appetite, inflammation, and sexual arousal. PT-141 (Bremelanotide), the FDA-approved melanocortin agonist for hypoactive sexual desire disorder in premenopausal women, illustrates how one receptor family can span several body systems.