[Carcinogenic potential of estrogens used in breeding].

The oestrogens that are used in husbandry are oestradiol (natural compound), zeranol (non-steroid drug) and stilbenes such as diethylstilboestrol (D.E.S.). Oestrogens present carcinogenic activity especially on target organs (cervix uteri, corpus uteri, breast). Oestrogens, except perhaps D.E.S., do not initiate cancer directly, but may influence carcinogenesis by their hormonal properties. In these conditions it is possible to define rules of use which can protect the health of consumers. It is necessary to take into account the no-hormonal effect level, and the metabolism after oral administration. Oestradiol and zeranol, when used in good husbandry practice are not toxic, but D.E.S. must be banned and controlled.