Glossary
Research-methodology and pharmacology terms, defined in plain language. Understanding these is most of what separates reading research from being persuaded by it.
- Beyond-use date
- The date after which a prepared solution should not be used, distinct from a manufacturer's expiry date for an unopened product.
- Reconstitution
- Bioavailability
- The proportion of an administered quantity that reaches systemic circulation intact. Peptides administered orally typically have very low bioavailability because they are degraded in the gastrointestinal tract, which is why route matters so much in this category.
- PharmacokineticsRoute of administration
- Biomarker
- A measurable biological characteristic. Moving a biomarker is easier than changing an outcome, and the two should never be reported as if they were equivalent.
- Surrogate endpoint
- Blinding
- Concealment of group allocation from participants, investigators, or both. Without it, expectation can influence both what participants report and how investigators measure it.
- Randomised controlled trial
- Certificate of analysis
- A document reporting analytical testing of a specific batch. Its value depends on whether the testing laboratory is independent and whether the certificate corresponds to the batch actually received.
- Concentration
- Mass per unit volume, for example micrograms per millilitre. Two containers holding the same total mass have different concentrations if different solvent volumes were used.
- Reconstitution
- Confidence
- A separate axis from evidence level, describing how settled the finding is. A serious hypothetical concern and a well-established mild one are different things, and collapsing them into one score loses that distinction.
- Evidence level
- Contraindication
- A situation in which a substance should not be used, as stated in authoritative labelling. We show contraindications only when an authoritative source states one, and we never infer them.
- Interaction
- DOI
- Digital Object Identifier, a permanent identifier for a published work that resolves even if the publisher's URL changes.
- PMID
- Endpoint
- The outcome a study was designed to measure. A study can only support a conclusion about its own endpoints, and a primary endpoint carries far more weight than a secondary or exploratory one.
- Surrogate endpoint
- Evidence level
- Our A through X scale describing how strong the underlying research is for one specific claim. It is graded per claim, never per compound, because the same compound can have strong evidence for one endpoint and none for another.
- Confidence
- GH axis
- The hypothalamic-pituitary pathway governing growth hormone. GHRH analogues act on the pituitary receptor; ghrelin-receptor secretagogues act on a different receptor in the same axis.
- IGF-1
- GIP
- Glucose-dependent insulinotropic polypeptide. Its contribution to the effect of dual agonists remains a subject of scientific debate.
- Incretin
- GLP-1
- Glucagon-like peptide-1. Receptor agonists in this class have the largest randomised evidence base of any compound category in this catalogue.
- Incretin
- Half-life
- The time for the concentration of a substance to fall by half. After roughly five half-lives, about 97% has been eliminated. Half-life determines how often a substance was administered in a study.
- PharmacokineticsSteady state
- IGF-1
- Insulin-like growth factor 1, produced largely in the liver in response to growth hormone. Frequently measured as a proxy for growth hormone exposure over time.
- GH axisBiomarker
- In vitro
- In cell culture or a test system rather than a living organism. An in-vitro result establishes that something can happen in that system, not that it happens in a person.
- Preclinical
- Incretin
- Gut hormones, principally GLP-1 and GIP, released after eating that augment insulin secretion in a glucose-dependent way and influence gastric emptying and appetite.
- GLP-1GIP
- Interaction
- A situation in which one substance affects another's behaviour or effect. An identified interaction does not establish harm, and the absence of an identified interaction does not establish safety.
- Contraindication
- Lyophilised
- Freeze-dried. Many peptides are supplied as a lyophilised powder because the dry form is more stable than the solution.
- Reconstitution
- Meta-analysis
- Statistical pooling of results from multiple studies. Quality depends entirely on the studies included; pooling weak or heterogeneous studies does not produce a strong conclusion.
- Systematic review
- NCT number
- The registration identifier for a study on ClinicalTrials.gov. Registration before enrolment is what makes it possible to detect selectively reported results.
- PMID
- Pharmacokinetics
- What the body does to a substance: absorption, distribution, metabolism, and elimination. Distinct from pharmacodynamics, which is what the substance does to the body.
- Half-lifeBioavailability
- Placebo
- An inactive comparator. Placebo groups often show measurable change, which is why a result without a placebo comparison says very little.
- Randomised controlled trial
- PMID
- PubMed Identifier, a unique number for a record indexed in PubMed. Where we have verified one it links directly to the source; where we have not, we say so rather than publishing an identifier that may not resolve.
- DOINCT number
- Preclinical
- Research conducted in animals or in cell culture, before human study. The large majority of preclinical findings do not translate to humans, which is why we separate this evidence rather than blending it.
- In vitroTranslation
- Randomised controlled trial
- A study in which participants are allocated to groups by chance. Randomisation is what allows a difference between groups to be attributed to the intervention rather than to how participants were selected.
- BlindingPlacebo
- Reconstitution
- Dissolving a lyophilised (freeze-dried) solid in a solvent to produce a solution of known concentration. Concentration equals the mass of material divided by the volume of solvent.
- ConcentrationLyophilised
- Research use only
- A labelling phrase. It is not a legal exemption. FDA has taken enforcement action where such labelling was contradicted by website evidence of intended human use, so the phrase does not change what a product actually is.
- Route of administration
- How a substance enters the body. Topical, oral, subcutaneous, intramuscular, intranasal, and intravenous routes can produce completely different exposure from the same quantity. Evidence from one route does not transfer to another.
- Bioavailability
- Steady state
- The point at which the amount entering the body over an interval equals the amount eliminated. Reached after roughly five half-lives of repeated administration at a constant interval.
- Half-life
- Surrogate endpoint
- A measurable substitute for an outcome that matters. A biomarker change is a surrogate; it is not the same as the outcome it stands in for, and surrogates have repeatedly failed to predict real outcomes.
- EndpointBiomarker
- Systematic review
- A structured review using a prespecified search and inclusion strategy. The prespecification is what distinguishes it from a narrative review that selects supportive studies.
- Meta-analysis
- Translation
- The step from animal or laboratory finding to human effect. Most compounds that work in animal models do not work in humans, and animal quantities expressed per kilogram do not convert to human quantities by simple arithmetic.
- Preclinical