A SARM (selective androgen receptor modulator) is a non-steroidal small molecule that binds the androgen receptor and is designed to produce tissue-selective transcriptional activity — activity in muscle and bone with reduced activity in prostate and skin. Chemically they are not steroids: the main scaffolds are aryl-propionamides (ostarine, andarine), quinolinones, and bicyclic hydantoins, with RAD-140 and LGD-4033 among the most cited.
Why the selectivity claim is a hypothesis
Selectivity is attributed to ligand-specific receptor conformations that recruit different coregulator sets in different tissues, plus the fact that non-steroidal ligands are not substrates for 5-alpha-reductase or aromatase. The evidence base is largely rodent and cell work plus phase 1 and 2 human trials in cachexia and muscle wasting; no SARM has completed a successful phase 3 programme or reached FDA approval, and hepatic and lipid signals were reported in several trials.
Status is part of the definition. SARMs are prohibited by WADA at all times, the FDA has issued public warnings against consumer use, and US legislative proposals have repeatedly sought to schedule them. Everything sold here is research use only and not for human consumption.
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.