Are Peptides Steroids?
A chemistry-first guide to peptide and steroid structures, hormone families and where SARMs fit.
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Three labels, three kinds of information
- Peptide
- A structural term for molecules made of amino-acid residues connected by peptide bonds. The definition covers naturally occurring molecules and synthetic chains that meet the same structural description.[1]
- Steroid
- A structural term for compounds based on the characteristic four fused-ring steroid nucleus and recognized derived skeletons. IUPAC allows related skeletons with ring scissions, expansions or contractions, so a rigid four-ring checklist is not the whole definition.[2]
- SARM
- A pharmacology label for a selective androgen receptor modulator. It describes receptor activity and selectivity; the exact compound still needs its own structural classification.[7][8]
Peptides vs steroids vs SARMs
| Question | Peptides | Steroids | SARMs |
|---|---|---|---|
| What defines the label? | Amino-acid residues connected by peptide bonds.[1] | A characteristic steroid nucleus or a recognized derived skeleton.[2] | Selective modulation of the androgen receptor; one scaffold is not implied.[7][8] |
| Example | Oxytocin has a peptide structure.[3] | Testosterone has the characteristic cyclopenta[a]phenanthrene-based steroid structure.[4] | S-40503 and S42 are examples from the SARM literature, with different structural descriptions.[7][8] |
| Does it name a hormone role? | No. Some peptides are hormones; many are not. | No. Some steroids are hormones; the structural label alone does not specify function. | It names androgen-receptor pharmacology. |
Chemical class and hormone function are separate
“Peptide” and “steroid” answer a chemistry question: what kind of molecular structure is this? “Hormone” answers a biology question: does the molecule act as a signaling substance? One word does not replace the other.
Oxytocin and testosterone make the distinction concrete. PubChem describes oxytocin as a cyclic nine-amino-acid peptide hormone, while the testosterone record gives an IUPAC name built on a cyclopenta[a]phenanthrene skeleton. These are examples of a peptide hormone and a steroid hormone, respectively.[3][4][5][6]
The steroid-hormone family also contains different groups. A review of human steroid biosynthesis describes glucocorticoids and mineralocorticoids from the adrenal cortex, alongside androgen precursors, and discusses androgen and estrogen production in the gonads.[6] That is why “steroid hormone” is broader than either “anabolic steroid” or “corticosteroid.” Those narrower labels refer to different families and actions; they should not be used as synonyms for every steroid.
Natural peptides and research products
A peptide can occur in a living system or be made synthetically. Its structural classification comes from its amino-acid chain and bonds, not from whether it was isolated from tissue or synthesized in a laboratory. IUPAC’s definition is structural and does not make natural origin a requirement.[1]
“Research peptide” describes how a product is presented or what context its supplier assigns to it. It is not an additional chemical class. The label alone cannot show that a material matches a named sequence, that it has a particular purity, or that results from a paper apply to it.
Where SARMs fit
A SARM is discussed for its activity at the androgen receptor and the selectivity profile reported for that particular compound. That pharmacology label does not mean every SARM shares one chemical skeleton.
The distinction appears in the literature itself. Hanada and colleagues described S-40503 as a novel nonsteroidal SARM in rat models of osteoporosis. Min and colleagues described S42 as a novel synthetic steroid that works as a SARM in rat and cell experiments.[7][8] These papers support a narrow point about terminology: “SARM” does not automatically mean “nonsteroidal.” They do not establish comparative human effects or outcomes.
Chemical class does not decide sport or legal status
Being a peptide rather than a steroid does not make a compound permitted. WADA’s 2026 Prohibited List bans anabolic agents at all times: anabolic-androgenic steroids under S1.1, and SARMs such as enobosarm (ostarine) and LGD-4033 under S1.2. Its S2 class bans peptide hormones and related substances, including growth hormone, its releasing factors and secretagogues, and its S0 class for non-approved substances names BPC-157.[9]
In the United States, anabolic steroids are Schedule III controlled substances under 21 CFR 1308.13.[10]
A vial or route does not define the chemistry
Packaging, route and physical form describe how a product is presented or delivered. They do not identify the molecular bonds or carbon skeleton that define a peptide or steroid. The same structural class can appear in different forms, and two products in the same format can contain molecules from different classes.
Classification also cannot establish safety, quality, regulatory status or human evidence. Those questions require their own source-specific assessment.
A quick way to read the label
Start with the exact compound name and, where available, its sequence or molecular structure. Then check whether the source refers to that same compound and what the study actually measured.
For a longer introduction to peptide structure, see What Are Peptides? For one peptide family, see the GHRH Peptides comparison.
Our Research Standards
Definitions follow the IUPAC Compendium of Chemical Terminology, compound descriptions follow PubChem, and sport and US legal status follow the WADA 2026 Prohibited List and the eCFR, all checked on October 20, 2026. No therapeutic, performance, human-use or veterinary-use claim is made here.
Frequently Asked Questions
Are peptides steroids?
No. Peptides are defined by amino-acid residues joined by peptide bonds. Steroids are defined by a characteristic steroid nucleus and related derived skeletons. These terms classify molecular structure.
Can a peptide be a hormone?
Yes. Some hormones are peptides and others are steroids. Oxytocin is a peptide hormone; testosterone is a steroid hormone. The word hormone describes a signaling role, while peptide or steroid describes chemical structure.
Are SARMs steroids?
Not always. SARM describes androgen-receptor modulation and selectivity. Published studies describe both a nonsteroidal SARM, S-40503, and a synthetic steroid SARM, S42, so check the exact compound.
Are corticosteroids and anabolic steroids the same?
No. Corticosteroids are glucocorticoids such as cortisol and mineralocorticoids such as aldosterone, made in the adrenal cortex, plus their synthetic analogues. Anabolic-androgenic steroids are testosterone and its synthetic derivatives. Both are steroids by structure, but they belong to different hormone families with different actions.
Does a vial, tablet or injection tell me whether a compound is a peptide or steroid?
No. A vial, tablet or injection describes how a product is packaged or given. Only the molecule’s structure shows whether it is a peptide or a steroid.
Sources
- International Union of Pure and Applied Chemistry. Peptides. IUPAC Compendium of Chemical Terminology, 5th ed., online version 5.0.0 (2025), entry P04479. IUPAC entry. DOI: 10.1351/goldbook.P04479.
- International Union of Pure and Applied Chemistry. Steroids. IUPAC Compendium of Chemical Terminology, 5th ed., online version 5.0.0 (2025), entry S06005. IUPAC entry. DOI: 10.1351/goldbook.S06005.
- National Center for Biotechnology Information. PubChem Compound Summary for Oxytocin, CID 439302. PubChem record.
- National Center for Biotechnology Information. PubChem Compound Summary for Testosterone, CID 6013. PubChem record.
- Gimpl G, Fahrenholz F. The oxytocin receptor system: structure, function, and regulation. Physiol Rev. 2001;81(2):629–683. doi: 10.1152/physrev.2001.81.2.629. PMID: 11274341.
- Schiffer L, Barnard L, Baranowski ES, et al. Human steroid biosynthesis, metabolism and excretion are differentially reflected by serum and urine steroid metabolomes: A comprehensive review. J Steroid Biochem Mol Biol. 2019;194:105439. doi: 10.1016/j.jsbmb.2019.105439. PMID: 31362062. Open-access full text.
- Hanada K, Furuya K, Yamamoto N, et al. Bone anabolic effects of S-40503, a novel nonsteroidal selective androgen receptor modulator (SARM), in rat models of osteoporosis. Biol Pharm Bull. 2003;26(11):1563–1569. doi: 10.1248/bpb.26.1563. PMID: 14600402.
- Min L, Yanase T, Tanaka T, et al. A novel synthetic androgen receptor ligand, S42, works as a selective androgen receptor modulator and possesses metabolic effects with little impact on the prostate. Endocrinology. 2009;150(12):5606–5616. doi: 10.1210/en.2009-0405. PMID: 19854864.
- World Anti-Doping Agency. The 2026 Prohibited List: International Standard, in force from 1 January 2026; sections S0, S1 and S2. WADA 2026 Prohibited List (PDF).
- Electronic Code of Federal Regulations. 21 CFR 1308.13, Schedule III, paragraph (f): anabolic steroids. eCFR.
This is a focused terminology comparison, not a systematic review. The SARM examples are preclinical papers and are cited only to show that the label spans compounds with different structural descriptions.