Metabolism Of 4-14c-Ethynyl Oestradiol In Women

ETHYNYL oestradiol was synthesized 30 years ago1 and since then has been used therapeutically as an orally active potent oestrogen. The use of this compound (and its 3-methyl ether, mestranol) has increased greatly in the past 15 years because it is a component of the oral contraceptive pill. No previous study of the metabolism of the compound has been carried out in humans. In spite of its widespread use and the fact that the oestrogenic component is generally regarded as being responsible for most of the side effects associated with the combined oral contraceptives, it seemed important to determine the rate and mode of excretion of ethynyl oestradiol as a preliminary to a more detailed investigation of its metabolism. The present communication describes some aspects of the metabolism of 4-14C-ethynyl oestradiol in women.