Reference
76 clinician-reviewed definitions for the peptide, GLP-1, hormone, regenerative-medicine, compounding, and clinical-research terms that recur across the Regen Therapy wiki, blog, and catalog. Every entry is a standalone "[Term] is..." definition with a stable anchor link.
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Short-chain signaling molecules and the receptor systems they act on. Most peptides on this list are not FDA-approved and are dispensed only as compounded preparations after a clinician evaluation.
A peptide is a short chain of amino acids - typically two to fifty residues - linked by peptide bonds. Peptides act as signaling molecules in the body and, when synthesized as pharmaceutical-grade ingredients, they sit between small molecules and full-length proteins in size and behavior.
An amino acid is one of the twenty standard organic compounds the body uses as building blocks for peptides and proteins. Their order in a chain determines a peptide's three-dimensional shape and which receptors it can engage.
A receptor agonist is any molecule that binds a cellular receptor and activates its downstream signaling. Most therapeutic peptides on this site are agonists - they imitate an endogenous signal at a specific receptor (for example, GLP-1 or GHRH) rather than blocking one.
A subcutaneous injection is a delivery route that deposits a medication into the fatty tissue just under the skin using a short, fine needle. Most compounded peptide and GLP-1 preparations are dispensed for subcutaneous self-administration with detailed clinician instructions.
BPC-157 is a 15-amino-acid sequence derived from a protein in human gastric juice, studied in preclinical models for tendon, ligament, and gut-mucosa repair. It is not FDA-approved and was placed on the FDA's 503A Category 2 bulks list in 2023.
GHK-Cu is a copper-binding tripeptide (glycyl-L-histidyl-L-lysine) studied in dermatology and wound-healing research for its effects on collagen synthesis and skin remodeling. It is most commonly compounded as a topical preparation.
Thymosin Beta-4 is a 43-amino-acid actin-binding protein that has been studied widely for tissue-repair, anti-inflammatory, and angiogenic signaling. It is not FDA-approved.
Thymosin Alpha-1 is a 28-amino-acid peptide naturally produced by the thymus and studied as an immune modulator with a long international history in viral and oncology adjunct care. It is not FDA-approved in the United States.
GHRH (growth-hormone-releasing hormone) is a hypothalamic peptide that stimulates the anterior pituitary to release growth hormone in pulses. Synthetic GHRH analogs such as CJC-1295 and tesamorelin extend that natural pulse to support clinician-directed protocols.
A GHRP (growth-hormone-releasing peptide) is a synthetic ghrelin-receptor agonist that prompts the pituitary to release a pulse of growth hormone. Ipamorelin is the most commonly prescribed example because of its relative selectivity for the GH axis.
CJC-1295 is a GHRH analog engineered for sustained activity, used in clinician-directed protocols to support the body's own pulsatile growth-hormone and IGF-1 release. It is not FDA-approved.
Ipamorelin is a selective ghrelin-receptor agonist (a GHRP) that stimulates pulsatile growth-hormone release with comparatively little effect on cortisol or prolactin. It is most often paired with a GHRH analog such as CJC-1295.
Tesamorelin is a stabilized GHRH analog that is FDA-approved (as Egrifta) for HIV-associated lipodystrophy and that has been studied for visceral-fat reduction in adults.
MOTS-c is a 16-amino-acid mitochondrial-derived peptide encoded inside the mitochondrial 12S rRNA, studied for its role in metabolic homeostasis, insulin sensitivity, and exercise capacity.
SS-31 is a mitochondrial-targeted peptide that binds cardiolipin on the inner mitochondrial membrane and is studied for cellular-energy and cardiovascular research. It is not FDA-approved.
Epithalon is a four-amino-acid pineal-derived peptide bioregulator studied in Russian gerontology research for circadian and putative telomere-related effects. It is not FDA-approved.
PT-141 is a melanocortin-receptor agonist studied for central effects on sexual desire and FDA-approved (as Vyleesi) for hypoactive sexual desire disorder in premenopausal women. It acts on neural pathways rather than on blood flow as PDE5 inhibitors do.
Kisspeptin-10 is the active decapeptide fragment of kisspeptin-54 that drives GnRH release from the hypothalamus and sits at the top of the HPG axis. It is studied in endocrinology research for fertility and hormone-axis support.
Semax is a short heptapeptide derived from a fragment of ACTH (4-7), studied in Russian neuroscience research for nootropic and neuroprotective effects. It is most commonly compounded as an intranasal preparation.
Selank is a synthetic heptapeptide based on the immunomodulator tuftsin, studied in Russian psychopharmacology research for anxiolytic and cognitive effects. It is most commonly compounded as an intranasal preparation.
Incretin-based drugs and the receptor combinations behind today's metabolic and weight-management protocols.
GLP-1 (glucagon-like peptide-1) is an incretin hormone released from intestinal L-cells after eating. It potentiates glucose-dependent insulin release, slows gastric emptying, and signals satiety in the brain - the three actions that underpin every GLP-1 receptor agonist on the market.
A GLP-1 receptor agonist is a medication that binds and activates the GLP-1 receptor, mimicking the natural hormone over a longer half-life. Examples include semaglutide and liraglutide.
An incretin is a gut-derived hormone (most notably GLP-1 and GIP) released after a meal that augments insulin secretion in a glucose-dependent way. The incretin effect is the basis for the entire class of incretin-based therapies.
GIP (glucose-dependent insulinotropic polypeptide) is the second major incretin hormone, secreted by intestinal K-cells. Dual GLP-1 / GIP agonism is the mechanism behind tirzepatide.
A dual agonist is a single molecule engineered to activate two distinct receptors at therapeutic potency. In the GLP-1 class, tirzepatide (GLP-1 / GIP) is the most widely prescribed dual agonist.
A triple agonist is a single molecule engineered to activate three distinct receptors. In late-stage development, retatrutide is the most studied triple agonist - it engages the GLP-1, GIP, and glucagon receptors simultaneously.
Semaglutide is a long-acting GLP-1 receptor agonist FDA-approved for type 2 diabetes (as Ozempic and Rybelsus) and for chronic weight management (as Wegovy).
Tirzepatide is a dual GIP and GLP-1 receptor agonist FDA-approved for type 2 diabetes (as Mounjaro) and for chronic weight management (as Zepbound).
Retatrutide is an investigational triple agonist of the GLP-1, GIP, and glucagon receptors in late-stage clinical development for chronic weight management and related metabolic conditions. It is not FDA-approved.
Survodutide is an investigational dual glucagon and GLP-1 receptor agonist in late-stage clinical development for chronic weight management and metabolic dysfunction-associated steatohepatitis (MASH). It is not FDA-approved.
A compounded GLP-1 is a preparation of a GLP-1 receptor agonist (or a related incretin) prepared by a 503A or 503B pharmacy for an identified patient need, typically when the FDA-approved branded product is on the FDA shortage list. Compounded medications are not FDA-approved drug products.
Endogenous hormones, the receptors and binding proteins that regulate them, and the modulators clinicians use alongside hormone-replacement protocols.
A hormone is a chemical messenger produced by an endocrine gland (or by another tissue with endocrine activity) that travels through the bloodstream to act on distant target cells. Steroid hormones are derived from cholesterol; peptide hormones are short protein chains.
Testosterone is the principal endogenous androgen in men and a key hormone in women. It is FDA-approved for hypogonadism in men and is dispensed in many forms, including injectable esters, transdermal preparations, and compounded subcutaneous pellets.
Estradiol (E2) is the most potent of the three endogenous human estrogens, FDA-approved in many forms for menopausal hormone therapy and used in compounded preparations - including pellets - prescribed by a clinician.
Progesterone is an endogenous steroid hormone produced primarily by the corpus luteum and placenta. The micronized oral preparation Prometrium is FDA-approved, and compounded preparations are also dispensed inside hormone-replacement protocols.
DHEA (dehydroepiandrosterone) is an adrenal steroid hormone that serves as a precursor to both androgens and estrogens. Levels decline with age, and clinicians sometimes incorporate DHEA into hormone-optimization protocols.
SHBG (sex hormone-binding globulin) is a liver-produced glycoprotein that binds testosterone and estradiol in the bloodstream and regulates how much of each hormone is biologically available. SHBG is a routine lab measured alongside total testosterone.
The HPG axis (hypothalamic-pituitary-gonadal axis) is the feedback loop that connects hypothalamic GnRH, pituitary LH and FSH, and testicular or ovarian sex-hormone output. Many hormone protocols are designed around modulating, suppressing, or restarting this axis.
Hypogonadism is a clinical state in which the gonads produce insufficient sex hormones - testosterone in men, estradiol and progesterone in women - because of a problem in the gonad itself (primary) or upstream in the HPG axis (secondary).
An aromatase inhibitor is a medication that blocks the aromatase enzyme, which converts androgens to estrogens. Anastrozole is a representative example; aromatase inhibitors are used in oncology and, off-label, inside selected male hormone protocols.
A SERM (selective estrogen receptor modulator) is a class of compound that binds estrogen receptors and acts as an agonist in some tissues and an antagonist in others. Tamoxifen, raloxifene, and clomiphene are representative examples.
A PDE5 inhibitor is a medication that blocks phosphodiesterase type 5, allowing nitric-oxide / cGMP signaling to relax smooth muscle and increase blood flow. Sildenafil and tadalafil are the most widely prescribed examples and are FDA-approved for erectile dysfunction.
A bioidentical hormone is a hormone preparation whose molecular structure matches the endogenous human hormone. The term is descriptive only - bioidentical preparations may be FDA-approved finished drugs (for example, micronized progesterone) or compounded preparations.
Cellular-aging, mitochondrial, and tissue-repair concepts that frame the regenerative side of longevity medicine.
Regenerative medicine is a field of clinical practice and research focused on restoring tissue function using cells, biologics, and signaling molecules rather than replacing damaged tissue with mechanical or pharmacologic substitutes. Peptides, cell-derived factors, and exosomes all fall inside this umbrella.
A mitochondrion is the double-membraned organelle that produces most of a cell's ATP through oxidative phosphorylation. Mitochondrial dysfunction is a recurring theme in aging research, which is why mitochondrially active peptides such as MOTS-c and SS-31 attract attention.
NAD+ (nicotinamide adenine dinucleotide) is a coenzyme central to mitochondrial energy production and DNA-repair signaling. Tissue NAD+ levels decline with age, and clinicians use NAD+ infusions and NAD+ precursors as part of longevity-oriented protocols.
An NAD+ precursor is a small molecule the body converts intracellularly to NAD+ via the salvage pathway. Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are the most commonly studied precursors.
Cellular senescence is a state in which a cell exits the cell cycle but remains metabolically active and secretes inflammatory factors (the senescence-associated secretory phenotype, or SASP). Accumulation of senescent cells is one of the recognized hallmarks of aging.
A senolytic is a compound that selectively triggers apoptosis in senescent cells, with the goal of reducing the inflammatory burden they create. Senolytic combinations are an active area of clinical research; none are currently FDA-approved as senolytic therapies.
An exosome is a small extracellular vesicle (roughly 30 to 150 nanometers) released by most cell types that carries proteins, lipids, and RNA between cells. Mesenchymal-stem-cell-derived exosomes are studied as a paracrine signaling tool in regenerative protocols.
A mesenchymal stem cell (MSC) is a multipotent stromal cell that can differentiate into bone, cartilage, and fat lineages and that secretes a broad set of paracrine factors. Most of MSC therapy's effect is now attributed to that secreted signaling cargo rather than to engraftment.
Quantum cell factors is an umbrella term for the secreted signals - exosomes, growth factors, cytokines - released by mesenchymal stem cells and adjacent regenerative cell sources. Cell-factor preparations isolate that signaling cargo so the same effect can be delivered without administering whole cells.
AMPK (AMP-activated protein kinase) is an energy-sensing kinase that responds to a low ATP-to-AMP ratio by switching cells from anabolic toward catabolic metabolism. AMPK activation is a recurring mechanism in metabolic and longevity research.
mTOR (mechanistic target of rapamycin) is a kinase complex that integrates nutrient, energy, and growth-factor signals to control protein synthesis, autophagy, and cell growth. Modulating mTOR is a central theme in longevity research.
A growth factor is a secreted protein - VEGF, IGF-1, BDNF, and others - that binds a cell-surface receptor and drives cellular proliferation, differentiation, or survival. Many regenerative protocols target growth-factor signaling indirectly through peptides or cell-derived factors.
How prescription compounding works in the United States and the regulatory categories that determine which preparations a pharmacy can legally dispense.
A compounded medication is a prescription preparation made by a licensed pharmacy for an identified patient need under sections 503A or 503B of the Federal Food, Drug, and Cosmetic Act. Compounded medications are not FDA-approved drug products and are not generic equivalents of any branded medication.
A 503A pharmacy is a traditional compounding pharmacy that prepares patient-specific compounded medications under a valid prescription. 503A facilities are regulated primarily by state boards of pharmacy with FDA oversight on certain bulks substances.
A 503B outsourcing facility is an FDA-registered compounding facility that can prepare larger batches of compounded medications without patient-specific prescriptions, subject to current good manufacturing practice (cGMP) requirements. Wells Pharmacy Network operates both 503A and 503B services.
A bulk drug substance is the active pharmaceutical ingredient a compounding pharmacy starts with - the powder or liquid before it is formulated into a finished preparation. The FDA maintains lists that determine which bulks 503A and 503B facilities may legally use.
The 503A bulks list is the FDA's published categorization of bulk drug substances eligible (Category 1), still under review (Category 2 - presumptively not eligible), or ineligible for use in 503A patient-specific compounding. Several research peptides, including BPC-157, sit on Category 2.
USP <797> is the United States Pharmacopeia chapter that sets sterility, environmental, and personnel standards for pharmacies preparing sterile compounded medications. Injectable peptides and hormones are produced under USP <797> conditions.
USP <800> is the United States Pharmacopeia chapter that defines handling standards for hazardous drugs in healthcare settings, including specific compounded preparations. It governs personnel protection, ventilation, and disposal practices.
FDA-approved means a finished drug product has been reviewed by the U.S. Food and Drug Administration and authorized for marketing in the United States for the indications listed on its label. Compounded preparations are not FDA-approved drug products even when their active ingredient is.
Off-label use is the legal practice of prescribing an FDA-approved medication for an indication, dose, route, or population not listed on its FDA-approved label. Off-label prescribing is widespread in endocrinology and longevity medicine and is at the discretion of the licensed clinician.
cGMP (current good manufacturing practice) is the FDA's regulatory framework that governs the design, monitoring, and control of pharmaceutical manufacturing processes. 503B outsourcing facilities must comply with cGMP; 503A pharmacies operate under a separate set of state-led standards.
The FDA drug shortage list is the federal registry of finished drug products in confirmed shortage. When a medication is on the list, 503A and 503B pharmacies are permitted, under specific conditions, to compound preparations using the active ingredient to fill that gap.
The trial-design and pharmacology vocabulary that recurs across our wiki, blog, and product pages.
A clinician evaluation is a structured intake - history, symptoms, goals, labs, and risk review - performed by a licensed clinician to determine whether a particular protocol is appropriate for a particular patient. On Regen Therapy, eligibility for any compounded preparation is decided here, not at checkout.
A randomized controlled trial (RCT) is a clinical study in which participants are randomly assigned to an intervention or a control condition so that the treatment effect can be estimated with minimal confounding. RCTs are the standard for evaluating drug efficacy and safety.
A double-blind study is a trial in which neither participants nor investigators know who is assigned to the active intervention versus the control until the data is unblinded. Double-blinding minimizes the risk of expectation bias on both sides.
A placebo is an inactive preparation given to the control group in a trial so the measured effect of the active intervention can be separated from the effect of receiving any treatment. Placebo response is itself a real, measurable phenomenon.
Phase 1, 2, and 3 trials are the three main stages of human drug development. Phase 1 evaluates safety and pharmacokinetics in small groups; Phase 2 evaluates efficacy and dose in patients with the target condition; Phase 3 confirms efficacy and safety in large pivotal studies that support FDA review.
An Investigational New Drug (IND) application is the FDA submission a sponsor must clear before administering a new drug to humans in the United States. Many of the experimental peptides discussed on this site lack any active IND, which is why their clinical use is research-informed and individualized.
A primary endpoint is the prespecified outcome measure a clinical trial is designed and powered to evaluate. Secondary endpoints are exploratory and cannot, on their own, support a regulatory claim.
Pharmacokinetics (PK) is the study of how the body absorbs, distributes, metabolizes, and excretes a drug over time. Half-life, peak concentration (Cmax), and area under the curve (AUC) are core PK parameters that shape dosing schedules.
Pharmacodynamics (PD) is the study of what a drug does to the body - its biochemical and physiological effects, the receptors it engages, and the dose-response relationships that follow. PK and PD together explain how a given dose produces its observed effect.
Half-life is the time it takes for the plasma concentration of a drug to fall to half its starting value. Half-life is a primary determinant of dosing frequency - long-half-life GLP-1 agonists are dosed weekly, short-half-life PDE5 inhibitors are dosed on demand.
The Compound Wiki is the long-form companion to this glossary - one page per active compound with mechanism, dosing forms, safety, and the Regen Therapy protocols that include it.
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