Glossary

48 terms that come up constantly in this field and are almost never explained properly.

Glossary

48 terms that come up constantly in this field and are almost never explained properly.

Agonist: A substance that binds a receptor and activates it, mimicking the natural signal of the body. An antagonist binds the same receptor and blocks it instead.
Amino acid: The individual building block of peptides and proteins. Twenty of them, combined in different orders, make up essentially all the protein in the human body.
Analogue: A molecule deliberately modified from a natural one, usually to make it last longer in the body or bind more selectively. An analogue is not the same substance as the peptide it was derived from and can behave differently.
ATA: Atmospheres absolute, the unit used to describe pressure inside a hyperbaric chamber. One ATA is normal pressure at sea level, so the figure indicates how far above normal the chamber is run.
Brown adipose tissue: A form of fat that generates heat rather than storing energy. It is the tissue most often discussed in cold exposure research, though how much adults have and how much it matters remain open questions.
Certificate of Analysis: A document reporting laboratory testing on a specific batch. It describes what one sample of one batch contained when tested - it is not an approval, a safety assessment or a guarantee about any other batch.
Circadian rhythm: The roughly 24-hour internal cycle that governs sleep timing, hormone release, body temperature and much else. Light is its strongest external cue, which is why light timing dominates sleep research.
Cortisol: A hormone that follows a daily rhythm, normally peaking shortly after waking. It is commonly described as the stress hormone, though its everyday role in regulating energy availability is broader than that label suggests.
Double-blind: Neither the participants nor the researchers assessing them know who received which intervention. This guards against expectation shaping both how people feel and how outcomes get recorded.
Effect size: How big a difference an intervention actually made, as opposed to how confident we are that a difference exists. A statistically significant result can have an effect size too small to notice.
GLP-1: Glucagon-like peptide-1, an incretin hormone. Several licensed medicines are GLP-1 receptor agonists, meaning they activate the same receptor the natural hormone does. In the UK those medicines are prescription-only and may not lawfully be advertised to the public.
Half-life: The time taken for the amount of a substance in the body to fall by half. Short half-lives are one reason many peptides behave very differently in a living body than in a test tube.
Heat shock proteins: Proteins produced in response to heat and other stresses that help other proteins fold correctly and recover from damage. They are the most commonly cited mechanism in sauna research.
Hormesis: The idea that a mild, controlled stress can prompt an adaptive response that leaves the system more resilient. It is the framework usually invoked to explain why heat, cold and exercise might be beneficial - and it implies that more is not automatically better.
HPLC: High-performance liquid chromatography, the standard laboratory technique for separating the components of a mixture. It is how a purity percentage on a certificate is usually produced.
Hyperbaric: Above normal atmospheric pressure. Hyperbaric oxygen therapy involves breathing oxygen in a pressurised chamber, which increases the amount dissolved in the blood.
IGF-1: Insulin-like growth factor 1, produced largely by the liver in response to growth hormone. It is often measured as a proxy for growth hormone activity because it is more stable in the blood.
In vitro: Literally "in glass" - an experiment done on cells or tissue in a dish rather than in a living organism. Useful for working out mechanism, but a dish is not a body and results routinely fail to carry over.
In vivo: An experiment done in a living organism, whether animal or human. In vivo results sit above in vitro results on the evidence ladder but say nothing on their own about which species was studied.
Incretin: A gut hormone released in response to food that influences insulin release, stomach emptying and appetite signalling. GLP-1 and GIP are the two best studied.
Irradiance: How much light energy reaches a given area per second, usually given in milliwatts per square centimetre. Together with time it determines dose, which is why distance from a light source changes the exposure entirely.
Lyophilised: Freeze-dried. Peptides are commonly supplied as a lyophilised powder because most are far more stable dry than in solution.
Marketing authorisation: The licence a medicine must hold to be legally marketed, granted only after a regulator has assessed evidence of quality, safety and efficacy. A medicinal product that has no marketing authorisation is an unlicensed medicinal product.
Medicinal product by function: A legal test under which a substance counts as a medicine because of what it does in the body, regardless of how it is labelled or marketed. Calling something a research chemical does not decide the question.
Melatonin: A hormone released as darkness falls that signals biological night. It is a timing signal rather than a sedative. In the UK, melatonin supplied as a medicine is prescription-only.
Meta-analysis: A statistical method for combining the results of multiple studies into a single estimate. More reliable than any one study, but bounded by the quality of what went into it.
MHRA: The Medicines and Healthcare products Regulatory Agency, the UK body responsible for assessing medicines and medical devices and for enforcing medicines law.
Near-infrared: Light just beyond the visible red part of the spectrum, commonly around 800 to 850 nanometres. It penetrates tissue further than visible red light, which is why devices often combine the two.
Peptide: A short chain of amino acids joined together. The distinction from a protein is one of size rather than kind: chains shorter than roughly fifty amino acids are usually called peptides, longer ones proteins.
Photobiomodulation: The technical term for red light therapy: the use of specific red and near-infrared wavelengths to influence cellular activity. The leading proposed mechanism involves light absorption in the mitochondria.
Placebo: An inactive comparison given so that the effect of expectation can be separated from the effect of the intervention itself. Without one, improvement over time cannot be attributed to the treatment.
Preclinical: Research done before any human testing, typically in cells and animals. The large majority of compounds that look promising preclinically never go on to work in people.
Prescription-only medicine: A licensed medicine that may lawfully be supplied only against a prescription following clinical assessment. The lawful route to one is a qualified prescriber and a registered pharmacy.
Primary endpoint: The main outcome a trial was designed and powered to measure, declared before it starts. Results on other measures are exploratory, and treating them as the headline finding is a well-known way to overstate a result.
Publication bias: The tendency for studies showing an effect to be published while studies showing nothing are not. It means the published literature on a topic is systematically more positive than the research that was actually carried out.
Purity: The proportion of a sample that is the stated compound. A high purity figure says nothing about whether the remaining fraction is harmless, and nothing at all about whether the compound is safe or effective.
Randomised controlled trial: A study in which participants are assigned by chance to receive the intervention or a comparison, so that differences in outcome are less likely to be explained by who ended up in which group. The strongest single study design for testing whether something works.
Receptor: A protein on or in a cell that a signalling molecule binds to, triggering a response. Most peptide effects are explained by binding to a particular receptor.
Reconstitution: Dissolving a freeze-dried powder back into liquid. It is a chemistry step, not a formality: temperature, solvent and handling all affect whether the molecule survives intact.
Replication: Independent researchers repeating a study and getting a comparable result. A finding that has never been replicated should be treated as a hypothesis rather than as established.
Research use only: A label indicating a substance has not been assessed or approved as a medicine for human use. It is a statement about regulatory status, not a quality standard, a safety assessment or a legal safe harbour.
Secretagogue: A substance that prompts the body to release something it already makes, rather than supplying it directly. Growth-hormone secretagogues are described as acting on the pituitary to prompt growth hormone release.
Sequence: The specific order of amino acids in a peptide. The sequence determines the shape the molecule takes and therefore what it can bind to, which is why changing one amino acid can change a compound entirely.
Sleep pressure: The build-up of the drive to sleep across waking hours, associated with accumulating adenosine in the brain. It is one of two systems governing sleep, the other being circadian timing.
Statistical significance: A statement that a result is unlikely to have arisen by chance alone, conventionally at p less than 0.05. It says nothing about whether the effect is large or whether it matters.
Systematic review: A review that searches for all the evidence on a question using a pre-declared method, rather than selecting studies that suit an argument. The method is what distinguishes it from an ordinary review article.
WADA prohibited list: The list published by the World Anti-Doping Agency of substances and methods banned in sport. It is a separate regime from medicines law: a substance that is not itself prohibited by criminal law can still cause an athlete to fail a test.
Yellow Card scheme: The UK system for reporting suspected side effects of medicines and problems with medical devices. Reports can be submitted by patients as well as healthcare professionals.

Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.