Testosterone is commonly known as the primary hormone produced by men necessary for health, well being and development and function of male sexual process.  Testosterone cream (for example TestoCreams) is applied to the skin around the genetalia  supplying the body with testosterone at times that production is otherwise impeded.
According to the National Institutes of Health (NIH) Doctors are regularly prescribing testosterone cream for men suffering from infertility, male hypogonadism and decreased muscle mass due to low testosterone.
Read more at LiveStrong