| Abstract: | The antifertility action of various sex hormones is discussed. 20 years ago it was determined that Norethynodrel and Norethindrone, newly synthesized progestins, were effective oral contraceptives in women, and that their action was attributed to inhibition of ovulation. The author, skeptical of their effectiveness and mode of action, began to study some non-steroidal compounds claimed to prevent pregnancy in laboratory animals when administered orally soon after mating. When these antiestrogens, Norethynodrel, H241, and other estrogenic compounds were subjected to tests in laboratory animals, it was found that all these compounds, with varying degree of potency, caused a rapid egg transport to the uterus and expulsion of eggs from the uterus, but that ethinyl estradiol was the most effective one in this respect. It was determined through a number of experiments that the mechanism of action of estrogen administered soon after mating can be attributed not only to the early arrival of eggs from the tube into the uterus before they are able to survive in the uterus, but also to the expulsion of eggs from the uterus. When progestins are administered before ovulation, the transportation of eggs is much earlier than normal. Degeneration of eggs also occurs during such treatment. Based on the fact that degeneration of eggs occurred when eggs at 1 stage of development were transferred into the uterus of an advanced stage as demonstrated in many species by numerous workers, the degeneration of eggs in progestin-treated animals can be expected. It is concluded that the effectiveness of steroidal oral contraceptives is due to their attack on several processes of reproduction: they not only inhibit ovulation, but can inhibit fertilization and also cause the degeneration of eggs. It is hoped that through further research, in the future new ways will be found to regulate fertility without hazardous side effects. |
