Dutasteride is a drug used in the treatment of benign prostatic hyperplasia. This refers to, in effect, the enlargement of the prostate gland. This condition can have damaging lifestyle consequences to those afflicted, as it not only disrupts urine output during the day, but also at night. One of the reasons for the enlargement is old age. A second reason, however, focuses on testosterone. Dutasteride functions to disrupt the conversion of testosterone to dihydrotestosterone. By disrupting this process, it prevents the further enlargement of the prostate gland. As a result, though, long-term severe side-effects can include erectile dysfunction and prostate cancer.