COMPARISON OF THE ANTI-FERTILITY AND SEX HORMONAL ACTIVITIES OF SEX HORMONES AND THEIR DERIVATIVES

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Abstract
The following effects exerted by sex steroids were measured: androgenic, oestrogenic, and progestational effects; the inhibition action on gonadotrophic function in castrated animals; and the inhibitory action on ovulation and blastocyst implantation in intact animals. The steroids investigated consisted of oestradiol and its ethinyl and methoxyethinyl derivatives, oestrone, oestriol, testosterone, progesterone, and certain synthetic gestagens derived from nortestosterone, i. e. norethisterone, norethynodrel, and ethinyl-oestrenol. Oestradiol and its derivatives show potent anti-gonadotrophic activity, a relatively less potent anti-ovulatory effect, and a marked inhibitory action on implantation. Progesterone, on the other hand, which has only a very weak inhibitory effect on gonadotrophic function, shows an anti-ovulatory activity which, though inferior in absolute terms to that of oestradiol, is still appreciable, whereas it exerts almost no effect at all on implantation. With regard to its activity ratios, testosterone occupies a position mid-way between the two female hormones. Norethisterone, norethynodrel, and ethinyl-oestrenol have a more potent effect on gonadotrophic function than progesterone. The activity ratios for the effects of these three compounds on ovulation and implantation are comparable to those of oestradiol or progesterone, depending on the relative intensity of their oestrogenic and progestational action. The nature of the endocrine changes produced by these compounds are discussed with reference to the inhibition of ovulation and implantation.