Testosterone phenylpropionate is primarily used in hormone replacement therapy (HRT) to treat conditions caused by low testosterone levels in men, such as hypogonadism. It helps restore normal testosterone levels, improving symptoms like fatigue, low libido, and muscle loss. Additionally, it is utilized in the treatment of certain types of breast cancer in women, where it can help inhibit tumor growth. In the field of sports and bodybuilding, it is sometimes misused as an anabolic steroid to enhance muscle mass and performance, although this is not a medically approved application. The compound’s slow-release properties make it effective for maintaining stable hormone levels over an extended period.