Glossary
SARM (Selective Androgen Receptor Modulator)
SARMs are non-steroid androgen receptor ligands designed to act selectively by tissue. Their chemistry, the selectivity idea and their US regulatory position.
SARMs — selective androgen receptor modulators — are small molecules without a steroid skeleton that attach to the androgen receptor and are intended to switch on transcription in a tissue-dependent way — active in muscle and bone, less active in prostate and skin. Structurally these are not steroids: the main chemical classes are the aryl-propionamides (for example ostarine or andarine), the quinolinones and the bicyclic hydantoins, while RAD-140 and LGD-4033 feature among the most frequently cited compounds.
Selectivity remains a hypothesis
The proposed basis for selectivity is that each ligand induces its own receptor conformation, which recruits a different set of coregulators depending on the tissue, and on top of that, ligands lacking a steroid core are not processed by aromatase or by 5-alpha-reductase. The evidence rests mostly on rodent and cell experiments, supplemented by phase 1 and 2 studies in humans with muscle wasting or cachexia; no SARM has successfully completed a phase 3 programme or gained FDA approval, and several trials reported liver and lipid signals.
Regulatory status belongs to the definition. WADA bans SARMs both in and out of competition, the FDA has published warnings against their use by consumers, and US lawmakers have repeatedly proposed scheduling them.
Related terms and material
myostatin · FDA-approved vs research-grade · preclinical. Reference material: SARMs collection, RAD-140, LGD-4033. Further reading: SARMs in 2026: regulatory status.