Andarine, also known as S4 or S-4, is a selective androgen receptor modulator that was developed to treat muscle wasting diseases, and cancer patients who were wasting away. S-4 is an anabolic agonist that is effective and does not have the same side effects as anabolic-androgenic steroids. Its effectiveness is primarily due to its substrate affinity for 5α-reductase, which produces DHT in the prostate. Unfortunately the benefits that SARMs such as andarine (S-4) may provide to clinical medicine have the potential for misuse in sports where athletes and/or their handlers may seek to gain unfair advantage with the assumption that these compounds are undetectable by anti-doping laboratories. SARMs are therefore prohibited for use by the International Federation of Horseracing Authorities and the World Anti-Doping Agency (WADA).