Peptide glossary: plain-English terms with primary sources

A short chain of amino acids linked together. Peptides and proteins are made of the same parts; what separates them is mostly length. FDA's 2020 rule treats a chain of more than 40 amino acids as a protein, and the agency noted that scientists do not agree on one exact cut-off. Insulin shows how fuzzy the line is: it is often called a peptide hormone, yet it is 51 amino acids long, so under that FDA rule it counts as a protein.

Primary sources NCI Dictionary of Cancer Terms (NIH): peptide [V] Federal Register, 2020 final rule defining "biological product" [V]

On this site Plain-English explainer · Approved medicines versus wellness peptides

One of the small molecules that join up to build peptides and proteins. The body uses 20 common ones. A peptide's name often hints at its length, such as a tripeptide for three or a 44-amino-acid chain for tesamorelin.

Primary sources NCI Dictionary of Cancer Terms (NIH): amino acid [V]

On this site Plain-English explainer

A hormone made by the pituitary gland, a small gland at the base of the brain. It helps steer growth and how the body handles sugar and fat. Medicines made from it exist and are a separate category from peptides that prompt the body to release its own.

Primary sources NCI Dictionary of Cancer Terms (NIH): growth hormone [V]

On this site Sermorelin versus growth hormone

Growth hormone-releasing hormone: the signal the hypothalamus sends to the pituitary, asking it to release growth hormone. Sermorelin and tesamorelin are lab-made relatives of it, which is why the posts treat them as one family.

Primary sources DailyMed, EGRIFTA WR (tesamorelin) label [V]

On this site Tesamorelin · Sermorelin

A substance that prompts the body to release something it already makes. A growth hormone secretagogue nudges the pituitary to release growth hormone, rather than supplying the hormone itself. Ipamorelin was described in a 1998 paper as the first selective one.

Primary sources Raun et al., 1998, European Journal of Endocrinology (PubMed abstract) [V] Sigalos and Pastuszak, 2018, Sexual Medicine Reviews (PubMed abstract) [V]

On this site CJC-1295 and ipamorelin

Insulin-like growth factor 1, a growth signal made mostly by the liver when growth hormone is active. Studies often measure it because it rises when growth hormone signalling rises, which makes it a convenient marker.

Primary sources DailyMed, EGRIFTA WR (tesamorelin) label [V]

On this site Tesamorelin

GLP-1 is a natural gut hormone that helps regulate appetite and blood sugar. "GLP-1 medicines" are approved drugs built to act on the same receptor, including semaglutide (Wegovy) and tirzepatide (Zepbound). They are peptide medicines with full FDA labels, which is the main contrast with the research peptides covered elsewhere on this site.

Primary sources DailyMed, WEGOVY (semaglutide) label [V] DailyMed, ZEPBOUND (tirzepatide) label [V]

On this site Approved, compounded and research-labeled GLP-1

An enzyme in cells that rebuilds telomeres, the protective caps on the ends of chromosomes. Epitalon research is often framed around it. A result in cultured cells does not by itself show the same effect in a person.

Primary sources NCI Dictionary of Cancer Terms (NIH): telomerase [V]

On this site Epitalon

A drug is approved when its maker shows FDA, usually through a New Drug Application, that it is safe and effective for a stated use. Approval attaches to a specific product and use, not to an ingredient in general. When a post says "no U.S. approval found", it means we searched FDA records and found none.

Primary sources FDA, drug development step 4: FDA drug review [V] DailyMed (National Library of Medicine) [V]

On this site Approved versus wellness peptides · What "legal" means

The filing a developer submits to ask FDA to approve a drug. It collects everything known about the product, from lab work to phase 3 trial results, along with the proposed label.

Primary sources FDA, drug development step 4: FDA drug review [V]

On this site Approved versus wellness peptides

The filing that lets a sponsor ship and study an unapproved drug in people across state lines. It normally comes before the clinical trials that later support an NDA.

Primary sources FDA, Investigational New Drug (IND) application [V] FDA, drug development step 3: clinical research [V]

On this site Evidence ladder

A pharmacist or physician prepares a medicine for an individual patient instead of dispensing a mass-produced approved one. FDA states that compounded drugs are not FDA-approved, so the agency does not review them for safety, effectiveness or quality before they reach patients. The law sets conditions on who may compound and with which ingredients.

Primary sources FDA compounding Q&A page [V] FDA page on the 503A bulks list [V]

On this site Approved versus wellness peptides · FDA compounding categories

The part of federal drug law covering compounding by state-licensed pharmacies and physicians, usually for a prescription written for one patient. A bulk ingredient must meet one of three conditions: it follows a USP monograph, it is part of an FDA-approved drug, or it appears on FDA's 503A bulks list.

Primary sources FDA page on the 503A bulks list [V] FDA, 503A bulk drug substances category list (PDF) [V]

On this site FDA compounding categories

The part of federal drug law for outsourcing facilities: compounders that register with FDA, pay an annual fee and re-register each year. A 503B facility may use a bulk ingredient only if it is on FDA's 503B bulks list or the finished drug is on the drug shortage list.

Primary sources FDA page on the 503B bulks list [V] FDA, registered outsourcing facilities [V]

On this site FDA compounding categories

An active ingredient in its raw form, before it is turned into a finished medicine. Compounders may only use certain bulk ingredients. FDA keeps a separate bulks list for 503A and for 503B, and a substance reaches either list through FDA review and rulemaking, not by being popular.

Primary sources FDA page on the 503A bulks list [V] FDA page on the 503B bulks list [V]

On this site FDA compounding categories

FDA's holding arrangement while it works through nominated ingredients. It sorts them into categories and describes when the agency does not intend to take enforcement action. It is a statement about FDA's priorities, not an approval and not a safety finding.

Primary sources FDA page on the 503A bulks list [V] FDA page on the 503B bulks list [V]

On this site FDA compounding categories · Regulation timeline

An interim FDA group for ingredients that were nominated with enough supporting information for FDA to evaluate them. FDA says it does not intend to act against a compounder using one if the policy's conditions are met. Being in category 1 is not an approval.

Primary sources FDA, 503A bulk drug substances category list (PDF) [V] FDA page on the 503A bulks list [V]

On this site FDA compounding categories

An interim FDA group for nominated ingredients the agency has flagged as possibly carrying significant safety risks. FDA's page gives substance-specific reasons, such as possible immune reactions for some peptides or an absence of any human exposure data for others. The page also keeps a separate section for substances whose nominations were later withdrawn.

Primary sources FDA, bulk substances that may present significant safety risks (category 2 page) [V]

On this site FDA compounding categories · Status of 14 peptides

An interim FDA group for nominated ingredients where the paperwork did not give FDA enough supporting information to evaluate them. They can be nominated again with more. It reflects missing information, not a verdict.

Primary sources FDA page on the 503A bulks list [V] FDA page on the 503B bulks list [V]

On this site FDA compounding categories

A nomination that the person who submitted it later withdrew. On FDA's category 2 page, withdrawn nominations sit in their own section and the agency's safety text stays visible. A withdrawal changes the paperwork, not what FDA has said about the risks.

Primary sources FDA, bulk substances that may present significant safety risks (category 2 page) [V]

On this site Status of 14 peptides · BPC-157: what changed

The formal process an agency uses to add or change a rule: a proposal is published, the public comments, and a final rule follows. Adding a substance to the 503A bulks list happens this way, which is why it can take years.

Primary sources FDA page on the 503A bulks list [V] Federal Register, the daily journal where proposals and final rules appear [V]

On this site Regulation timeline

Review by the White House Office of Information and Regulatory Affairs, which looks at significant draft rules and policy documents before an agency puts them out. Reginfo.gov lists what is under review. When a post says "under White House review", this is the step.

Primary sources Reginfo.gov, pending review record for RIN 0910-ZD94 [V]

On this site Regulation timeline · What "legal" means

A letter FDA sends to a company it believes broke the law, asking for corrections. FDA itself cautions that matters in a letter may have changed after it was sent, so a letter is a snapshot, not a final ruling.

Primary sources FDA, warning letters [V]

On this site Marketing red flags · Tesamorelin

FDA's term for a product it treats as a drug even though it has no approval. Whether something counts as a drug depends on its intended use, which FDA can read from how a product is described and promoted.

Primary sources FDA, warning letters [V]

On this site Marketing red flags · Tesamorelin

A label saying a product is meant for laboratory research, not for people. Anti-doping and drug regulators both treat the label as no guarantee of anything: USADA calls such products risky, and in a 2026 warning letter FDA pointed to a seller's own website wording when judging intended use.

Primary sources USADA, 2026 Clean Sport Handbook (PDF) [V] FDA, warning letters [V]

On this site Marketing red flags · GLP-1 explained

Under the law, intended use decides whether a product counts as a cosmetic or a drug, not what it contains. That is why a skincare ingredient such as GHK-Cu can sit in cosmetics while claims of treating a condition would point toward drug rules.

Primary sources FDA cosmetics page on intended use [V]

On this site GHK-Cu human studies · Marketing red flags

An action to take a defective or risky drug off the market or to warn people about it. FDA publishes recall announcements and marks a recall as terminated once it judges the corrective work complete.

Primary sources FDA, drug recalls [V]

On this site A published recall, explained

MedWatch is FDA's reporting program for problems with medical products, open to patients, consumers and health professionals. An adverse event is any health problem that happens during or after treatment. It may or may not have been caused by the treatment, which is why single reports are signals to look into, not proof.

Primary sources FDA, MedWatch safety reporting program [V]

On this site Marketing red flags · Telehealth and compounded drugs

DailyMed is the National Library of Medicine's database of current drug labels (prescribing information). The posts use it to check whether a name has an approved product: a search for 13 of the 14 peptides covered here returns nothing, while tesamorelin returns labels.

Primary sources DailyMed (National Library of Medicine) [V]

On this site Status of 14 peptides

The Pharmacy Compounding Advisory Committee is a panel of outside experts that advises FDA on compounding questions. Its votes are recommendations; the agency makes the decision, and a vote by itself changes no list.

Primary sources FDA, Pharmacy Compounding Advisory Committee meeting page [V]

On this site Status of 14 peptides · Regulation timeline

A committee result we know from news coverage rather than from FDA's own minutes. The site marks these [S], and where outlets disagree on a tally it says so.

Primary sources AJMC, "FDA Panel Backs 6 Peptides for Compounding" [V]

On this site Status of 14 peptides · How we source

Research done before any testing in people, such as lab-dish and animal studies. It asks whether something is plausible and whether it might cause harm. It does not show that something works in a person.

Primary sources FDA, drug development step 2: preclinical research [V] NCI Dictionary of Cancer Terms (NIH): preclinical study [V]

On this site Evidence ladder

In vitro means done in a dish or test tube with cells or tissue outside a living body. In vivo means done in a living animal or person. Both appear in preclinical research.

Primary sources NCI Dictionary of Cancer Terms (NIH): in vitro [V] FDA, drug development step 2: preclinical research [V]

On this site Evidence ladder

Phase 1 trials are small and look mainly at safety. Phase 2 trials involve more people and look at whether the drug seems to work and which side effects show up. Phase 3 trials are larger and are the usual basis for an approval decision.

Primary sources FDA, drug development step 3: clinical research [V]

On this site Evidence ladder · Tesamorelin

A study in which chance decides who gets which treatment, so the groups start out comparable. It is the usual way to separate a treatment's effect from everything else going on.

Primary sources NCI Dictionary of Cancer Terms (NIH): randomized clinical trial [V]

On this site Evidence ladder

A placebo is an inactive stand-in that looks like the real treatment. In a double-blind study neither the participants nor the researchers know who got which until the end, which makes bias less likely.

Primary sources NCI Dictionary of Cancer Terms (NIH): placebo [V] NCI Dictionary of Cancer Terms (NIH): double-blind study [V]

On this site Evidence ladder

A study that records what happens to people without assigning a treatment. It can show patterns but is weaker at showing cause, because the groups may differ in other ways.

Primary sources NCI Dictionary of Cancer Terms (NIH): observational study [V]

On this site Evidence ladder · MOTS-c

A systematic review gathers studies on one question using a stated search method. A meta-analysis goes a step further and pools their numbers. Both are only as good as the studies they collect.

Primary sources NCI Dictionary of Cancer Terms (NIH): meta-analysis [V]

On this site Evidence ladder · BPC-157 human studies

A measurable sign in blood, tissue or elsewhere that reflects a process in the body. Studies often report biomarker changes because they are quicker to measure than health outcomes, but a better number is not the same as a better outcome.

Primary sources NCI Dictionary of Cancer Terms (NIH): biomarker [V]

On this site Epitalon · Evidence ladder

The identifier ClinicalTrials.gov gives a registered study. A registry entry shows that a trial exists and what stage it is at. Whether it has published results is a separate question.

Primary sources ClinicalTrials.gov [V]

On this site BPC-157 human studies

Information from people who actually received a substance, such as trial results or case reports. When FDA says it found none for a peptide, it is saying it has no record of how people respond.

Primary sources FDA, bulk substances that may present significant safety risks (category 2 page) [V]

On this site Status of 14 peptides · BPC-157 and TB-500

The tendency of a substance to provoke an immune reaction, such as the body making antibodies against it. FDA names it among the concerns on its category 2 page for some peptides.

Primary sources FDA, bulk substances that may present significant safety risks (category 2 page) [V]

On this site FDA compounding categories

The World Anti-Doping Agency publishes the Prohibited List each year. A substance goes on it when it meets two of three tests: it can raise performance, it poses a real or possible health risk, or it goes against the spirit of sport. The 2026 List took effect January 1, 2026.

Primary sources WADA, "WADA publishes 2026 Prohibited List" [V] WADA, 2026 Prohibited List (PDF) [V]

On this site Peptides and the WADA list

The List's catch-all class for pharmacological substances with no current government approval for human therapeutic use. Such substances are banned at all times, whether or not they are named. BPC-157 is named here.

Primary sources WADA, 2026 Prohibited List (PDF) [V]

On this site Peptides and the WADA list

The List's section for hormone-like peptides, growth factors and look-alike compounds. Sub-sections matter in the status table: S2.2.4 covers growth-hormone-releasing peptides such as sermorelin, tesamorelin and ipamorelin, and S2.3 covers thymosin-beta-4 and its derivatives such as TB-500.

Primary sources WADA, 2026 Prohibited List (PDF) [V]

On this site Peptides and the WADA list · Status lookup

The List's class for substances that alter metabolism. MOTS-c is named under S4.4.1.

Primary sources WADA, 2026 Prohibited List (PDF) [V]

On this site MOTS-c

The anti-doping principle that an athlete is responsible for whatever is found in their body, however it got there, including through a supplement with an inaccurate label.

Primary sources USADA, 2026 Clean Sport Handbook (PDF) [V]

On this site Peptides and the WADA list

Permission an athlete can apply for to use a listed substance for a documented medical need. It is arranged in advance through the athlete's anti-doping organization.

Primary sources USADA, 2026 Clean Sport Handbook (PDF) [V] WADA, "WADA publishes 2026 Prohibited List" [V]

On this site Peptides and the WADA list

This site's evidence labels. [V] means we checked the claim in a primary document such as an FDA page, a label or a published paper. [S] means a secondary source, such as press coverage, reported it. [U] means we could not verify it. They describe how we know something, not how important it is.

On this site How we source

The site's way of describing how far research has come, from cells and animals to small human studies, controlled trials and finally approval. It is a stage marker for what exists, not a judgment of any peptide.

On this site The evidence ladder · Status lookup