Glossary

Plain-language definitions of the terms used throughout PeptidePlotter. Bookmark this page or follow inline links to come back here.

Half-life (t½): The time associated with a halving during a specified phase of a concentration-time profile. Its interpretation depends on the product, route and measurement; a depot absorption phase and drug elimination are not interchangeable. Half-life alone does not choose a dose schedule or a treatment-start date.
Cmax: The highest observed or modelled concentration in a specified measurement interval. A single-dose peak and a steady-state peak are different endpoints. A higher concentration does not, by itself, establish a stronger or safer clinical effect.
Tmax: The time of a specified concentration peak, measured from a defined dose or interval start. The formulation, population, sampling schedule and single-dose or repeated-dose context belong with the value.
Bioavailability (F): The fraction of an administered dose that reaches systemic circulation. It depends on the exact product and route; an injection is not automatically equivalent to complete systemic availability. A measured concentration already reflects the absorption conditions of its study.
Steady state: A repeating concentration pattern approached under a stable repeated-dose regimen. A selected simulation duration does not by itself demonstrate that the pattern has stabilized. Changing the regimen or underlying assumptions changes the question.
Trough: A low point in a defined concentration interval. The level immediately before the next dose is often called a pre-dose trough, but it can differ from the interval minimum while accumulation is changing. A model trough does not set a universal laboratory-testing time.
Accumulation: When doses are given before the previous dose fully clears, levels build up over time. Long-half-life compounds accumulate significantly — troughs climb for weeks before stabilizing at steady state.
Ester: A chemical group attached to a hormone (e.g. testosterone) that controls its release rate. The ester is slowly cleaved by enzymes in the body, releasing the active hormone. Longer esters = slower release = longer half-life (e.g. cypionate vs. propionate).
Aromatization: The conversion of testosterone to estradiol (estrogen) by the aromatase enzyme. The amount of aromatization tracks total testosterone exposure — higher peaks and larger doses produce more E2 conversion.
SERM: Selective Estrogen Receptor Modulator. A drug that blocks estrogen at specific tissues (e.g. breast) without lowering systemic estrogen. Used in PCT and for gynecomastia treatment (e.g. tamoxifen, clomiphene).
AI (Aromatase Inhibitor): A drug that reduces estrogen production by blocking the aromatase enzyme (e.g. anastrozole, exemestane). Used on-cycle when estradiol climbs too high. Narrow therapeutic window — easy to overshoot and crash E2.
PCT (Post-Cycle Therapy): A term for medicines used in an attempt to support recovery after anabolic-androgenic steroid use. It is not one established regimen for everyone. Hormone concentrations, symptoms and sperm production are separate outcomes; clearance math does not establish treatment timing.
HPTA: Hypothalamic-Pituitary-Testicular Axis: the hormone-signalling system involving the hypothalamus, pituitary and testes. LH and FSH have different roles in testicular function. A plotted drug decline cannot measure recovery of that system.
GLP-1: Glucagon-Like Peptide-1. An incretin hormone that stimulates insulin, suppresses glucagon, slows gastric emptying, and reduces appetite. GLP-1 agonists (semaglutide, tirzepatide) are used for diabetes and weight loss.
Reconstitution: Preparing a product from a powder or concentrate using its specified diluent and instructions. The product or pharmacy information must establish compatibility, preparation and storage; an arithmetic calculator cannot supply those missing facts.
Subcutaneous (SQ) injection: Injection into the fatty tissue just under the skin (e.g. abdomen, thigh). Used for peptides, insulin, and GLP-1 agonists. Smaller needle gauge than intramuscular.
Intramuscular (IM) injection: Injection deep into muscle tissue (e.g. glute, quad, deltoid). Used for oil-based hormones (testosterone esters, nandrolone). Requires a larger-gauge needle than subcutaneous.
SARM (Selective Androgen Receptor Modulator): A non-steroidal compound that activates the androgen receptor in muscle and bone tissue while aiming to spare the prostate and other androgenic tissues. Investigational and not FDA-approved. Examples include ostarine (MK-2866) and ligandrol (LGD-4033).
Secretagogue: A compound that stimulates the body to release a hormone. Growth hormone secretagogues (like ipamorelin, MK-677) prompt the pituitary to release GH rather than introducing it directly.
GHRP (Growth Hormone Releasing Peptide): A class of peptides that stimulate GH release through the ghrelin (GHS-R1a) receptor. Examples: GHRP-6, GHRP-2, ipamorelin. They work through a different pathway than GHRH analogs, so stacking the two produces synergy.
GHRH (Growth Hormone Releasing Hormone): A hypothalamic peptide that stimulates the pituitary to release growth hormone in pulses. Synthetic analogs include sermorelin, CJC-1295, and tesamorelin.
Lyophilized: Freeze-dried. The term does not establish a product's diluent, suitability for injection, storage conditions or usable lifetime.
AUC (Area Under the Curve): The integral of concentration over a specified time interval. Comparisons require compatible units, measurement endpoints and study conditions. A modelled AUC is not a measured exposure or evidence of clinical benefit.
First-pass metabolism: The liver processes orally administered compounds before they reach systemic circulation. This destroys a large fraction of many drugs, which is why oral bioavailability is often low. Injectable and sublingual routes bypass first-pass.
Depot: The injection site acts as a reservoir (depot) that slowly releases the compound into the bloodstream. Oil-based esters and microcrystal suspensions create depots that extend release over days or weeks.
DPP-4: Dipeptidyl peptidase-4, the enzyme that rapidly degrades native GLP-1 (within 1-2 minutes). DPP-4 inhibitors (sitagliptin) extend the life of endogenous GLP-1. GLP-1 agonists like semaglutide are structurally modified to resist DPP-4.
WADA: The World Anti-Doping Agency publishes the Prohibited List and laboratory technical documents, among other standards. A substance's prohibited status and an analytical laboratory result are different questions.
Metabolite: A product of a substance's transformation in the body. An analytical method may target the parent substance, a metabolite or another marker. Their time courses need not match, and the target alone does not establish a universal detection duration.
Detection window: An observed detection interval under a specified study and analytical method. It depends on what was sampled and measured; the last observed positive sample does not establish when an uncollected later sample would become negative.
GC-MS: Gas chromatography coupled with mass spectrometry. It is one analytical approach for identifying and measuring compounds; the validated method, sample and target determine what a result means.
IRMS (Isotope Ratio Mass Spectrometry): Measurement of isotope ratios. In steroid testing, carbon-isotope comparisons between selected steroids and reference compounds can inform their origin. Testing is not limited to cases with an elevated testosterone/epitestosterone ratio.
T/E ratio: The ratio of testosterone to epitestosterone in urine, one marker within a steroid profile. Interpretation involves the relevant analytical rules and broader profile; a single ratio is not a prediction of a negative test.
HPGA: Hypothalamic-Pituitary-Gonadal Axis: signalling between the hypothalamus, pituitary and gonads. Describing this feedback system does not establish whether a person needs treatment after hormone exposure.
Negative feedback: The mechanism by which high levels of a hormone signal the body to produce less. Exogenous testosterone suppresses GnRH and LH through negative feedback, which is why the body stops producing its own testosterone during a cycle.
DHT (Dihydrotestosterone): A potent androgen converted from testosterone by the 5-alpha-reductase enzyme. DHT drives androgenic side effects like hair loss, prostate growth, and acne. Some compounds (DHT derivatives) are already in this form and cannot be further reduced.
5-alpha reductase: The enzyme that converts testosterone to DHT. Inhibitors like finasteride block this conversion. Compounds that are already DHT derivatives (like primobolan, masteron) are unaffected by 5-alpha reductase.
SHBG (Sex Hormone Binding Globulin): A protein that binds testosterone in the blood, rendering it inactive. Only free (unbound) testosterone is biologically active. High SHBG reduces free T even when total T is normal. Some compounds (like winstrol) lower SHBG.
Vermeulen formula: The standard equation for calculating free testosterone from total testosterone, SHBG, and albumin. Named after Dr. Alex Vermeulen. More accurate than direct analog-based lab tests for free T.
Insulin syringe: A syringe whose markings correspond to an insulin concentration scale. On a U-100 scale, 100 scale units represent 1 mL. That conversion is not universal across device scales, and syringe markings are not interchangeable with milligrams or another drug's biological units.
Lipolysis: The breakdown of fat (triglycerides) into free fatty acids for energy use. Compounds that promote lipolysis (like HGH fragment, clenbuterol, GLP-1 agonists) are studied for fat-loss applications.

Source context for revised definitions

These references explain PK measurement, recovery, laboratory testing and preparation. Their findings apply to their stated populations, products and methods; they do not validate the site's numeric models.

Educational use only — not medical advice. Definitions are simplified for accessibility; consult clinical literature for precise pharmacological detail.