INHIBITORY EFFECT OF VARIOUS STEROIDS ON GONADOTROPHIN HYPERSECRETION IN PARABIOTIC MICE1

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Abstract
A variety of steroids have been administered subcutaneously or orally into the castrated male partner of parabiotic mice to investigate their anti-gonadotrophic activity based on the inhibition of ovarian growth in the intact partner united with the castrated male. The data demonstrate that estrogenicity is most likely responsible for antigonadotrophic activity of the compound, but either androgenic or progestational potency of the steroid is not always proportional to its antipituitary action. According to the compound, especially in 19-norsteroids, the oral activity on the gonadotrophin inhibition is not always parallel with the subcutaneous potency. Norethynodrel and norethisterone, both of which are known as orally active anti-ovulatory agents, have roughly the same order of anti-gonadotrophic activity as that of estrone in the oral test. However, 6-methyl-17-acetoxyprogesterone, 17-1.methallyl- or 17-2.methallyl-19-nortestosterone, all of which are orally potent progestational substances, like progesterone itself do not show any significant inhibition of pituitary gonadotrophin when administered orally. Further, as a possible mechanism for the manifestation of anti-gonadotrophic action of various steroids, it is discussed that a part of the compound may convert into some estrogen-like substance in the body, the amount of which is able to inhibit gonadotrophin secretion but not enough to affect peripheral targets, although a major part of the steroid administered is responsible for the hormonal activities the compound may have.