INTERFERENCE OF THE ANTIHORMONE RU486 IN THE DETERMINATION OF TESTOSTERONE AND ESTRADIOL BY ENZYME-IMMUNOASSAY

The antihormone RU486 (mifepristone, 11 beta-(4-dimethylaminophenyl)-1 7 beta-hydroxy-17 alpha-(prop-1-ynyl)-estra-4,9-dien-3-one) is current ly used in many endocrinological studies and in clinical practice as a contraceptive agent. The results presented here indicate that the syn thetic steroid RU486 may interfere in determinations of testosterone a nd estradiol when using some commercial kits. Although the cross react ivity is low (0.30% for testosterone and 0.16% for estradiol), in anim al experiments RU486 doses higher than 5 mg/kg may produce false posit ive results in the estimation of plasma testosterone (specially in cas trated male or female mice) or estradiol concentrations, even in sampl es obtained 48 h after the administration of this antihormone. (C) 199 8 Elsevier Science B.V. All rights reserved.