[Skip to the reading](#reading) A little clarity, from Summer. [Summer](/) [The guides](/#the-guides)[Your questions](/#the-goals)[About Summer](/about/) **Explore +** [The guides](/#the-guides)[Your questions](/#the-goals)[About Summer](/about/)[Common questions](/faq/)[The glossary](/glossary/)[Contact](/contact/) [Summer](/)/peptide glossary Keep this page nearby # A little help with the words. This peptide glossary is a companion to the guides. Come back when an unfamiliar word interrupts the reading; there is no need to learn everything before you begin. [How Promise Peptides works↗](https://mypromise.com/products?utm_source=summer&utm_medium=affiliate&utm_campaign=glossary&utm_content=opening) Summer may earn money when readers become Promise patients. Promise Peptides prescribes now through licensed U.S. providers. A provider reviews each request and decides; not everyone qualifies. U.S. patients only. Availability varies by state and treatment. Compounded medicines are not FDA-approved. ## Words you may meet. **Peptide** A short chain of amino acids, the building blocks of proteins. The word identifies a kind of substance. It does not establish that a product is safe, approved or appropriate for a person. **Receptor** A part of a cell that receives a signal. When a guide says a medicine acts at a receptor, it is describing a target in the body, rather than an expected result for every person. **GLP-1 and GIP** Gut hormones involved in the body’s response to food. Semaglutide acts at GLP-1 receptors; tirzepatide acts at both GIP and GLP-1 receptors. The initials describe signals, not a ranking of treatments. **Compounded medicine** A medicine prepared to meet a particular patient’s needs. Compounded medicines are not FDA-approved. A provider’s prescription and a pharmacy’s decision about lawful preparation are separate steps. **FDA approval** A decision by the U.S. Food and Drug Administration about a specific medicine and its uses. It does not follow an ingredient name into all products that contain it. Approved semaglutide and tirzepatide products exist; compounded versions are not FDA-approved. **Topical** Placed on the skin. A topical cream and an injection are different forms. Evidence for one cannot establish what the other does. This distinction matters in the GHK-Cu guide. **Placebo** A comparison treatment with no active ingredient. Comparing groups can help researchers separate the effect of the substance being tested from changes that might have happened anyway. **Animal or cell study** Work in an animal model or cells in a laboratory. It can suggest a question for further research. It cannot establish a human treatment result or tell someone what to expect from taking a substance. **Nominated but withdrawn** A term on the FDA’s compounding safety page, current as of April 22, 2026. A request for consideration was withdrawn. That is not FDA clearance or approval, and the FDA’s safety concerns remain. **Licensed provider** A health professional authorized to make care decisions within their scope of practice. At Promise Peptides, a licensed U.S. provider reviews each request and decides whether to prescribe. Not everyone qualifies. ## When a question needs a provider. A consultation is a place for a licensed review of your health. It can end without a prescription. There is room for that answer too. [How Promise Peptides works↗](https://mypromise.com/products?utm_source=summer&utm_medium=affiliate&utm_campaign=glossary&utm_content=closing) Summer may earn money when readers become Promise patients. Promise Peptides prescribes now through licensed U.S. providers. A provider reviews each request and decides; not everyone qualifies. U.S. patients only. Availability varies by state and treatment. Compounded medicines are not FDA-approved. [Summer](/) Room for the questions. Care with the answers. ## Start somewhere - [The compound guides](/#the-guides) - [The goal guides](/#the-goals) - [Common questions](/faq/) ## A little context - [About Summer](/about/) - [The glossary](/glossary/) - [How we write and check](/method/) ## Keep in touch - [The reading shelf](/references/) - [Contact](/contact/) - [Read in Markdown](/glossary/index.md) Summer may earn money when readers become Promise patients. Summer Peptides is an independent guide and is not Promise Peptides. Summer is a place to read and ask better questions; it offers no clinic, pharmacy or shop, and these pages cannot give personal medical advice. Promise Peptides prescribes now through licensed U.S. providers. A provider reviews each request and decides; not everyone qualifies. U.S. patients only. Availability varies by state and treatment. Compounded medicines are not FDA-approved. If a provider prescribes, a licensed U.S. compounding pharmacy separately decides whether it can lawfully prepare the prescription. Compounded medicines are not FDA-approved. Promise is LegitScript-certified; that certification is not FDA approval. © 2026 Summer Peptides [How Promise Peptides works](https://mypromise.com/products?utm_source=summer&utm_medium=affiliate&utm_campaign=glossary&utm_content=footer)