Peptide Research Glossary

A protein that forms microfilaments inside cells, critical for cell structure, movement, and division. TB-500 (Thymosin Beta-4) primarily works by regulating actin polymerization — the assembly of actin monomers into filaments — facilitating cell migration to injury sites.

A molecule that binds to a receptor and activates it, producing a biological response. Peptide agonists mimic the action of naturally occurring hormones or signaling molecules. Example: semaglutide is a GLP-1 receptor agonist — it binds and activates GLP-1 receptors just as endogenous GLP-1 does, but with a much longer half-life.

The basic building block of peptides and proteins. There are 20 standard amino acids. Peptides are defined as chains of 2–50 amino acids; proteins are longer chains. The specific sequence of amino acids determines a peptide's 3D structure and function.

The formation of new blood vessels from pre-existing vasculature. Multiple peptides under research (BPC-157, TB-500, GHK-Cu) are studied for their pro-angiogenic properties, which may support healing by improving blood supply to damaged tissue.

A molecule that binds to a receptor and blocks or dampens its activation, preventing a biological response. The opposite of an agonist. Some peptides function as partial agonists, producing weaker responses than the full agonist.

A pituitary hormone that stimulates cortisol production from the adrenal cortex. Some GHRPs (especially GHRP-2 and GHRP-6 at high doses) can elevate ACTH and cortisol as a side effect. Ipamorelin is distinguished by NOT elevating ACTH at standard doses.

Sterile water containing 0.9% benzyl alcohol, used to reconstitute lyophilized peptides. The benzyl alcohol acts as a preservative, inhibiting bacterial growth and allowing the reconstituted solution to be used for multiple doses over 28–30 days. The preferred diluent for multi-use peptide vials.

Bacteriostatic water (BAC) contains 0.9% benzyl alcohol as a preservative — allows reconstituted vials to be used for up to 28–30 days with multiple injections. Sterile water contains no preservatives — must be used within 24 hours of reconstitution. For multi-dose peptide research, BAC water is always preferred.

The fraction of an administered dose that reaches systemic circulation in an active form. Subcutaneous peptide injection typically provides ~80–100% bioavailability. Oral administration of most peptides is essentially zero due to gastrointestinal proteolysis (enzyme degradation). Exceptions include some very small peptides like KPV and certain non-peptide GHS compounds.

A class of short (2–4 amino acid) tissue-specific regulatory peptides developed by Professor Vladimir Khavinson at the St. Petersburg Institute of Bioregulation. Examples: Epitalon (pineal), Cartalax (cartilage), Livagen (liver), Cortagen (cardiovascular). Studied for age-related normalization of tissue-specific gene expression.

A synthetic 15-amino-acid peptide derived from a sequence found in human gastric juice protein. Studied extensively in preclinical models for tissue repair, gut protection, anti-inflammation, and wound healing. See the BPC-157 Protocol for full dosing information.

The amount of peptide dissolved per unit volume of liquid, typically expressed as mg/mL or mcg/mL. Determined by dividing the total peptide amount by the volume of BAC water added. Example: 5 mg ÷ 2 mL = 2.5 mg/mL. Concentration determines how much liquid you draw per dose.

A glucocorticoid hormone produced by the adrenal cortex. Some GHRPs (particularly GHRP-2 and GHRP-6 at higher doses) can elevate cortisol via ACTH stimulation. Elevated cortisol in sustained protocols can be counterproductive for body composition goals. Ipamorelin specifically does not elevate cortisol at standard doses.

The duration of a continuous peptide research protocol, typically expressed in weeks. After a cycle, a washout period (break) is typically observed before re-initiation. Cycle lengths vary dramatically by compound: GLP-1 agonists may be used for 24–68 weeks; GHRPs for 8–16 weeks; bioregulator peptides in 10–20 day courses.

Protecting cells from damage or death. BPC-157 is described as having cytoprotective properties — it appears to protect cells in the gut lining, liver, and other organs from various chemical and physical insults in preclinical research.

A modification applied to CJC-1295 that allows it to covalently bind to serum albumin, dramatically extending its half-life from ~30 minutes (No DAC) to ~6–8 days (with DAC). CJC-1295 DAC enables once-weekly dosing; CJC-1295 No DAC must be dosed daily or multiple times per day.

The reduction in receptor response with repeated stimulation. Some GHRPs cause receptor desensitization with chronic use, requiring dosing breaks. Ipamorelin has a lower desensitization profile than GHRP-2 or GHRP-6, making longer protocols more sustainable.

Peptides made with D-form amino acids (mirror image of natural L-amino acids) are resistant to enzymatic degradation. DRI peptides reverse both the chirality (D-form) and the sequence direction, producing compounds with similar 3D shape to the original but dramatically improved stability. FOXO4-DRI uses this modification.

An enzyme that rapidly degrades natural GLP-1 in plasma (half-life of natural GLP-1: ~2 minutes). Semaglutide and other GLP-1 analogs are modified at position 8 to resist DPP-4 degradation, extending their half-lives to days rather than minutes.

Endogenous compounds are produced naturally inside the body. Exogenous compounds are introduced from outside. Research peptides are exogenous — they are synthesized in a lab and administered to the research subject. Some (like BPC-157) mimic endogenous sequences; others (like retatrutide) are novel compounds.

A phenomenon that can occur if BAC water is injected directly onto lyophilized peptide powder or if the vial is shaken. Foaming can degrade peptide structure. Always inject BAC water slowly down the inside glass wall of the vial, and swirl gently rather than shaking.

Repeatedly freezing and thawing a peptide solution causes physical stress on the peptide molecules, leading to aggregation and loss of potency. Reconstituted peptide solutions should NOT be frozen — they should be refrigerated at 2–8°C and used within their expiration window (typically 14–30 days).

A hypothalamic hormone that stimulates GH release from the pituitary. GHRH analogs (CJC-1295, Sermorelin, Tesamorelin) mimic this action. They amplify the amplitude of existing GH pulses rather than independently triggering new ones.

A class of synthetic peptides that stimulate GH release through ghrelin (GHS-R1a) receptors in the pituitary and hypothalamus. They independently trigger GH pulses rather than amplifying existing ones. Examples: GHRP-2, GHRP-6, ipamorelin, hexarelin.

The ghrelin receptor. GHRPs bind to this receptor to stimulate GH release. Also mediates appetite regulation — activation drives hunger (this is why GHRP-6 causes strong appetite stimulation).

An incretin hormone secreted from the small intestine in response to food. Like GLP-1, it enhances insulin secretion in a glucose-dependent manner. Tirzepatide is a dual GIP/GLP-1 agonist. Retatrutide adds glucagon receptor activation to GIP and GLP-1 agonism for triple-agonist activity.

An incretin hormone released from intestinal L-cells in response to food intake. It enhances insulin secretion, suppresses glucagon, slows gastric emptying, and reduces appetite via CNS pathways. Natural GLP-1 has a half-life of ~2 minutes; GLP-1 analogs (semaglutide, liraglutide) are engineered for extended half-lives.

Glycyl-L-Histidyl-L-Lysine complexed with copper (Cu²⁺). Naturally occurring in human plasma. Studied for skin remodeling, collagen synthesis, wound healing, and modulation of gene expression pathways relevant to aging and inflammation. See the GHK-Cu Protocol.

The time it takes for the plasma concentration of a compound to reduce by 50%. Determines dosing frequency. A compound with a 7-day half-life (semaglutide) can be dosed once weekly. One with a 30-minute half-life (CJC-1295 No DAC) requires daily dosing. Steady-state concentration takes approximately 4–5 half-lives to achieve.

The neuroendocrine system regulating the stress response through cortisol production. Certain GHRPs can activate this axis, producing cortisol and ACTH elevation. This is considered undesirable in many research contexts and is a key reason ipamorelin (which doesn't activate the HPA axis) is preferred.

The neuroendocrine system regulating reproductive hormone production (testosterone, estrogen). HCG, Gonadorelin, and Kisspeptin all act at different points in this axis. Understanding HPG feedback is essential for research involving these peptides.

A hormone produced primarily in the liver in response to GH stimulation. IGF-1 mediates most of growth hormone's anabolic effects. Used as a biomarker for GH axis activity. GHRH analogs and GHRPs increase IGF-1 indirectly through GH stimulation; IGF-1 LR3 is a direct long-acting IGF-1 analog.

A class of gut hormones that enhance insulin secretion in response to food intake. GLP-1 and GIP are the primary incretins. GLP-1 agonists (semaglutide), dual GIP/GLP-1 agonists (tirzepatide), and triple agonists (retatrutide) all work through incretin pathways.

A compound that is being studied in research but has not yet received regulatory approval for the application being researched. Most peptides on this site are investigational — they may have clinical trial data, but are not approved for self-administration. A few (semaglutide, tirzepatide, PT-141) have FDA approval for specific indications.

A measure of biological potency, defined by international standards for specific hormones. Used for HGH (≈3 IU per 1 mg) and HCG. NOT the same as syringe "units" — a U-100 syringe mark is a volume unit (0.01 mL per unit), not a biological potency unit. Always clarify which type of "unit" is being referenced.

A buildup of fatty tissue at injection sites caused by repeatedly injecting in the same location. Prevented by systematic site rotation — cycling between abdomen, outer thigh, upper arm, and other subcutaneous sites. Lipohypertrophic tissue has reduced and inconsistent drug absorption.

A preservation technique that removes water from a product by freezing it and then reducing pressure to allow the frozen water to sublimate (evaporate without becoming liquid). Produces a dry powder or cake that is highly stable for long-term storage. All research peptides are supplied as lyophilized powder.

A pituitary hormone that stimulates testosterone production in males (via Leydig cells) and triggers ovulation in females. HCG mimics LH's action by binding to the same receptor. Gonadorelin stimulates LH and FSH release from the pituitary.

A unit of mass equal to one-millionth of a gram. 1 mg = 1,000 mcg. Many peptides are dosed in micrograms (e.g., 250 mcg of BPC-157). Confusing mg and mcg creates 1,000-fold dosing errors — always verify the unit before calculating.

A unit of mass equal to one-thousandth of a gram. 1 g = 1,000 mg. Some peptides are dosed in milligrams (e.g., 2 mg of retatrutide per week). Always confirm whether a protocol specifies mg or mcg.

A unit of liquid volume. On a U-100 insulin syringe, 100 syringe units = 1.0 mL. Used to specify injection volumes after reconstitution math is performed. Do not confuse mL (volume) with mg (mass).

A signaling system involving alpha-MSH and its receptors (MC1R–MC5R) that regulates diverse functions including skin pigmentation, energy balance, sexual function, inflammation, and immune response. PT-141, KPV, and Melanotan II all act through melanocortin receptors.

A transcription factor that is a master regulator of inflammation. Activation of NF-κB upregulates many pro-inflammatory genes. Several peptides (KPV, BPC-157, GHK-Cu) are studied for their ability to inhibit NF-κB signaling as part of their anti-inflammatory mechanism.

A signaling molecule that causes vasodilation, supports angiogenesis, and plays roles in tissue repair. BPC-157 is hypothesized to exert some of its cytoprotective effects through NO pathway modulation.

A short chain of amino acids, typically defined as 2–50 amino acids long. Longer chains are proteins. Peptides act as biological signaling molecules, hormones, and regulators. Synthetic research peptides are laboratory-produced versions of naturally occurring peptides or novel analogs designed to mimic them.

Latin medical abbreviation meaning "as needed" rather than on a fixed schedule. PT-141 is a PRN compound — administered when needed rather than daily or weekly. As opposed to continuous use compounds like semaglutide or BPC-157 which are used on fixed schedules.

Proteolysis is the enzymatic breakdown of proteins and peptides. Proteases are the enzymes that perform this breakdown. Most peptides taken orally are rapidly degraded by gastrointestinal proteases, which is why most peptide protocols require subcutaneous injection to bypass GI degradation.

The natural pattern of GH secretion — released in discrete pulses (8–10 per day in healthy adults) rather than continuously. The largest pulse occurs during deep sleep. GHRH analogs and GHRPs stimulate GH release in ways that preserve this pulsatile pattern, which is more physiologically appropriate than continuous supraphysiological GH levels from exogenous HGH.

A protein (typically on the cell surface or inside the cell) that binds a specific signaling molecule (ligand) and produces a biological response. Peptides produce their effects by binding to specific receptors. GLP-1 receptors, ghrelin receptors, and melanocortin receptors are all targeted by peptides on this site.

The process of dissolving lyophilized (freeze-dried) peptide powder in bacteriostatic water to create an injectable solution. The concentration of the resulting solution is determined by: concentration (mg/mL) = total peptide amount ÷ BAC water volume. Use the PeptidEdge Calculator for automatic computation.

How a compound enters the body. Common routes for research peptides: subcutaneous (Sub-Q) — into fat layer under skin; intramuscular (IM) — into muscle; intravenous (IV) — directly into bloodstream; intranasal — through nasal passages; oral — by mouth (limited utility for most peptides).

A compound that causes another substance to be secreted. GHRPs and GHRH analogs are growth hormone secretagogues — they stimulate the pituitary to secrete more GH. The term distinguishes compounds that stimulate endogenous production from exogenous GH (like HGH 191AA), which directly provides the hormone.

Senescent cells are cells that have permanently stopped dividing but resist programmed cell death (apoptosis). They accumulate with age and secrete pro-inflammatory signals (SASP). Senolytics are compounds that selectively clear senescent cells. FOXO4-DRI is being studied as a senolytic in preclinical models.

A hypothalamic hormone that inhibits GH release (opposes GHRH). It provides the negative feedback loop that limits GH pulses. GHRH analogs and GHRPs work best when administered during troughs of somatostatin activity — which is why fasted administration and pre-sleep timing are recommended.

Injection into the fatty tissue layer directly beneath the skin, above the muscle. The standard route for most research peptides. Performed with an insulin syringe at a 45–90° angle into a pinched skin fold, typically at the abdomen, outer thigh, or upper arm.

An enzyme that can add telomere repeats to chromosome ends, potentially reversing telomere shortening. Telomere shortening is associated with cellular aging. Epitalon is studied for its hypothesized ability to activate telomerase in human somatic cells — one of the core longevity mechanisms being researched.

Protective caps on the ends of chromosomes, composed of repetitive DNA sequences. They shorten with each cell division and with age. When telomeres reach a critical minimum length, cells enter senescence or die. Telomere length is used as a biomarker of cellular aging.

The gradual increase of a dose over time to allow the body to adapt and to minimize side effects. All GLP-1 agonists (semaglutide, tirzepatide, retatrutide) use slow titration schedules to minimize GI side effects. Starting at a low dose and escalating over weeks is a core principle of most peptide protocols.

A compound that activates three different receptors. Retatrutide is a triple agonist at GLP-1, GIP, and glucagon receptors — hence its exceptional weight-loss efficacy in Phase 2 trials. The glucagon receptor component adds energy expenditure on top of the appetite reduction provided by GLP-1 and GIP.

The most common insulin syringe. U-100 means 100 units per mL — so each syringe unit = 0.01 mL of liquid. The markings are volume units, not dose units. For example, drawing to "20 units" means you've drawn 0.20 mL, not a specific amount of peptide — the peptide amount depends on the concentration of your reconstituted solution.

A key signaling protein that stimulates angiogenesis (new blood vessel formation). BPC-157 is hypothesized to promote angiogenesis partly through upregulating VEGF receptor expression, supporting tissue healing by improving local blood supply.

A small sealed glass container used to supply lyophilized peptide powder. Sealed with a rubber stopper (for syringe access) and an aluminum crimp cap. Always labeled with peptide name and total amount (e.g., "BPC-157 5mg"). Never opened by removing the stopper — always accessed by inserting a sterile needle through the rubber stopper.

The international organization that publishes the prohibited substances list for competitive sports. Many research peptides are WADA-prohibited — including BPC-157, TB-500, all GHRPs and GHRH analogs, IGF-1, and HGH. Researchers in competitive sports contexts must account for WADA status.

A break between research cycles during which the compound is not administered. Allows the body to re-sensitize to the compound and prevents receptor desensitization or axis suppression. Length varies by compound: GLP-1 agonists typically have no washout; GHRPs may benefit from 4–8 week breaks between 12-week cycles.