S-23 is a selective androgen receptor modulator (SARM) and has been studied and proven to increase muscle mass, reduce fat mass, and has a very high binding affinity to the androgen receptors. It is non-steroidal and has tissue-selective anabolic effects in muscle and bone while sparing other androgenic effects that come from anabolic-androgenic steroids (AAS). It also has been shown to decrease the prostate size in studies, which is the opposite of a very common negative side effect of anabolic steroids (enlargement of the prostate).