These three categories get discussed in the same breath, sold in the same corners of the internet, and confused in almost every conversation about them. They are not variations on a theme. They differ at the level of what the molecules are, which means everything downstream — mechanism, legal status, evidence base — differs too.
The molecular difference
Peptides are short chains of amino acids joined by peptide bonds. They are the same structural class as insulin and oxytocin — the body's own signalling format. Being amino-acid chains, they are digested when swallowed, which is why peptide pharmaceuticals are overwhelmingly injectable.
Anabolic steroids are modified derivatives of testosterone, built on the four-ring steroid skeleton. Entirely different chemistry: lipid-soluble small molecules that cross cell membranes and bind intracellular androgen receptors directly.
SARMs — selective androgen receptor modulators — are synthetic non-steroidal small molecules designed to hit the same androgen receptor as steroids while being more tissue-selective. Not peptides, not steroids: a third chemistry aimed at the steroid target.
So: one is a chain of amino acids, one is a modified hormone, one is a designed small molecule. The only thing they share is a customer base.
The mechanism difference
Peptides are signalling molecules — they bind cell-surface receptors and initiate cascades. GLP-1 receptor agonists work this way; so does every growth-hormone secretagogue. The compound tells a system to do something it already knows how to do.
Steroids and SARMs are anabolic agents acting on the androgen receptor, driving transcriptional programs in muscle and other tissues. Different receptor, different location (intracellular rather than surface), different biology entirely.
Anyone using "peptides" as a catch-all for performance compounds is flattening a genuine biochemical distinction — and usually the flattening is doing work for them.
The legal and regulatory difference
This is where the categories diverge most sharply, and where confusion is most costly.
Anabolic steroids are Schedule III controlled substances in the United States. Possession without a prescription is a criminal matter.
SARMs are not controlled substances in the same way, but FDA has issued warnings about them, and they are prohibited in sport by WADA. Several have been through failed or abandoned clinical programs. Selling them for human consumption draws enforcement.
Peptides span the widest range: some are approved drugs (semaglutide, tesamorelin), some are the subject of active compounding-policy proceedings, and many are sold only as research-use-only material with no approval for human use of any kind.
"It's just a peptide" is therefore not a statement about legality. The category contains FDA-approved medicines and unapproved research chemicals simultaneously.
The evidence difference
Peptides as a class contain the single best-evidenced compounds discussed anywhere in this space — the incretin trials enrolled thousands and were published in the New England Journal of Medicine — alongside compounds with nothing but rodent data.
SARMs have a scattering of early human trials, mostly from abandoned pharmaceutical programs. Steroids have decades of clinical literature, including well-documented risk profiles.
Aggregating these into one bucket destroys the only thing that actually matters: which specific compound, studied how, in whom. That question survives every category boundary, and it's the one worth asking.
Research use only. No compound discussed here is FDA-approved for any indication, and nothing on this page is medical or legal advice.
For research use only · Not for human or veterinary use · No compound discussed here is FDA-approved for any indication