RAD-140, also known as Testolone, is a type of selective androgen receptor modulator (SARM). It’s an investigational compound designed to mimic the effects of testosterone without causing the same level of potential side effects.

SARMs like RAD-140 bind to androgen receptors in the body, influencing their activity in a way that can potentially increase muscle mass and strength. They were initially developed to help with medical conditions like muscle wasting and osteoporosis. However, they’ve gained popularity in the fitness and bodybuilding communities for their purported ability to enhance performance and aid in building muscle.