Human evidence
Research involving people. The strength still depends on study design, sample size, comparator, endpoints, and risk of bias.
Glossary
Evidence terms
Definitions for the labels and research language used across peptide pages.
Preclinical evidence
Research in cells, animals, or other non-human systems. It can explain possible mechanisms, but human relevance still has to be shown separately.
Evidence level
A page-level label that summarizes the strongest reviewed evidence for the most relevant claimed uses.
Confidence
The editorial team's confidence in the bottom line after reviewing source quality, claim specificity, and unresolved uncertainty.
Evidence record
The visible trail of primary sources, regulator pages, trial records, DOI, PMID, NCT identifiers, and review notes behind a record.
Protocol
A dosing or use regimen. On Peptides Media, protocol language is tied to the source that reported it.
Anecdotal evidence
Individual reports from clinics, forums, or social media. They are uncontrolled and subject to placebo effects and reporting bias, so they can raise questions but cannot establish that something works.
FDA-approved
Reviewed by FDA for a specific use, in a specific product, with a labeled dose and controlled manufacturing. Approval applies to that product and use: not automatically to every other product containing the same molecule.
Compounded drug
A drug prepared by a compounding pharmacy under sections 503A or 503B of the FD&C Act. Compounded drugs are not FDA-approved, and FDA says it does not verify their safety, effectiveness, or quality before they are marketed.
503A bulk drug substance
A bulk substance a traditional compounding pharmacy may use only if it meets specific criteria: for example a USP monograph, being a component of an FDA-approved drug, or appearing on FDA's 503A bulks list. Many discussed peptides have been nominated and reviewed for this list.
Research-use-only (RUO)
Labeling for products sold for laboratory research rather than human use. RUO products are not reviewed for human safety, identity, or purity: 'for research use only' describes a regulatory status, not a quality mark.
Investigational
Being studied in formal clinical trials but not approved for general use. Evidence at this stage can be promising and still fail later, larger trials.
Off-label
Use of an approved drug for a purpose, population, or route outside its FDA-approved label. Off-label prescribing is legal and common, but the evidence for the unlabeled use has to be judged separately.
Certificate of analysis (COA)
A document reporting test results for a specific batch of a product. A COA is only as reliable as the laboratory and chain of custody behind it, and it covers one batch: not an entire product line.
Endotoxin
Bacterial cell-wall fragments that can contaminate injectable products and trigger fever or more serious reactions. Standard purity assays do not detect endotoxin; it requires specific testing.
Immunogenicity
The tendency of a substance to provoke an immune response. With peptides, the molecule itself, impurities, or aggregates can trigger antibody reactions, which is one reason product quality matters.
Intra-articular
Into a joint. Route matters when reading studies: a result from an intra-articular injection says little about the same compound taken orally or under the skin.
Subcutaneous injection
An injection into the fat layer just under the skin. It is the most common route discussed for self-administered peptide products.
Lyophilized
Freeze-dried. Many peptide products ship as a lyophilized powder that is reconstituted with liquid before use; stability and storage needs differ between the dry and reconstituted forms.
Bacteriostatic water
Sterile water containing a small amount of benzyl alcohol as a preservative, used to reconstitute injectable products so a vial can be drawn from more than once with reduced bacterial growth.
Study identifiers (PMID, NCT, DOI)
Stable identifiers for primary sources: a PMID points to PubMed, an NCT number to a ClinicalTrials.gov record, and a DOI to a published article. They let you check the actual source instead of trusting a summary.
WADA Prohibited List
The World Anti-Doping Agency's list of substances and methods banned in sport. Many peptides discussed online, including growth hormone secretagogues, are prohibited, so competitive athletes should verify status before any use.
Half-life
The time for blood levels of a substance to fall by half. It drives dosing frequency: a 30-minute half-life means multiple daily injections, while a one-week half-life supports weekly dosing.
Bioavailability
The fraction of an administered amount that actually reaches circulation. Most peptides have near-zero oral bioavailability because digestive enzymes break them down, which is why injection dominates the discussion.
Agonist
A substance that activates a receptor and produces a signal. Most discussed peptides are receptor agonists: they mimic a natural hormone's message.
Antagonist
A substance that blocks a receptor without activating it. Research uses antagonists to prove which receptor a compound's effect actually depends on.
GHS-R1a (ghrelin receptor)
The receptor for ghrelin, the hunger hormone. GHRP-class peptides, hexarelin, and ipamorelin act here to trigger growth-hormone release.
GHRH (growth hormone-releasing hormone)
The hypothalamic hormone that tells the pituitary to release growth hormone. Sermorelin, tesamorelin, and CJC-1295 are analogs of it, engineered to last longer than the natural signal.
GLP-1 and GIP
Incretin hormones that regulate insulin secretion and appetite. Semaglutide activates GLP-1 receptors; tirzepatide activates both GIP and GLP-1 receptors; retatrutide adds glucagon-receptor activity.
DPP-4
The enzyme that rapidly degrades natural GLP-1, GIP, and GHRH. Drugs like semaglutide and tesamorelin are engineered to resist it, which is how they last long enough to be useful.
Amino-acid sequence
The ordered chain of amino acids that defines a peptide, written in three-letter codes. The exact sequence is the compound's identity: even one substitution makes a different molecule.
Salt form
Many peptides are sold as salts (for example, acetate) for stability. The salt form changes weight and handling, and FDA has objected to compounded semaglutide products that used non-label salt forms.
LAL test
The laboratory test that detects endotoxin in injectable products. A standard purity assay is not an endotoxin test: a vial can pass HPLC and still carry bacterial fragments.
USP (United States Pharmacopeia)
The standards body whose monographs define identity, strength, and purity for drugs. A USP monograph is one of the paths for a bulk substance to be usable in 503A compounding.
CAS number
A unique identifier assigned to each chemical by the Chemical Abstracts Service. Useful for verifying that the name on a vial and the actual substance are the same thing.
Excipient
An inactive ingredient in a formulation: a filler, stabilizer, or preservative. Excipients can differ between approved, compounded, and gray-market versions of the same molecule.