The stilbene derivatives diethylstilbestrol (DES), dienestrol and hexestrol are synthetic oestrogens that have been demonstrated to be genotoxic and carcinogenic in both animals and humans. DES has been used commercially as a growth-promoting agent in livestock, as a human medication to help maintain pregnancy and in the treatment of prostate cancer in humans, but was removed from these uses due to human carcinogenicity issues. DES, dienestrol and hexestrol are excreted in urine primarily as glucuronide tracer.