RAD-140, also known as Testolone, is an investigational selective androgen receptor modulator developed to study androgen receptor activity and tissue-selective pharmacology. Preclinical research has examined its potential effects on skeletal muscle and bone tissues. Unlike approved testosterone therapies, RAD-140 is not an established human therapeutic medicine. Human clinical evidence remains limited, while potential concerns include liver injury, unfavorable lipid changes, hormonal suppression, cardiovascular effects, reproductive disturbances, and other endocrine abnormalities requiring further scientific evaluation.