Androgen receptor (selective)

Class

Selective androgen receptor modulator (SARM)

The androgen receptor (AR) is a nuclear hormone receptor that, upon binding testosterone or its more potent metabolite dihydrotestosterone, translocates to the cell nucleus and regulates genes governing muscle growth, bone density, and male secondary sexual characteristics. Because AR is expressed across many tissues, systemic androgen exposure produces both desired effects (increased lean mass, bone strength) and undesired ones (prostate growth, skin and hair changes, suppression of the body's own hormone production). Selective androgen receptor modulators, or SARMs, are nonsteroidal small molecules designed to activate AR in a tissue-selective manner, favoring anabolic actions in muscle and bone while producing comparatively weaker androgenic effects in the prostate and skin. This selectivity is achieved through the specific molecular shape of the ligand, which influences how the receptor folds and which cofactor proteins it recruits once bound. The broad rationale for pursuing this mechanism lies in conditions marked by muscle wasting, frailty, or bone loss, where an agent could preserve or restore lean tissue without the full spectrum of side effects associated with traditional anabolic steroids or testosterone replacement therapy.