The use of estrogens as postcoital contraceptive agents. Clinical effectiveness and potential mode of action

Tubal motility, oviduct flow, and ciliary activity are all influenced by estrogens. Tubal insufflation studies suggest that estrogens cause closure of the uterotubal junction in women. Estrogen action may reflect a release from modifications imposed by progesterone and may threaten the functional integrity of the corpus luteum under hypothalamic-hypophyseal control. Board and Bhatnagar have shown reduced progesterone levels with administration of diethylstilbestrol. Decrease of BBT following use of ethinyl estradiol and diethylstilbestrol support the theory of the luteolytic action of estrogen. After nidation, estrogens have no effect. Haspels reported on 2000 women treated with ethinyl estradiol (2-5 mg) or diethylstilbestrol (25-50 mg) administered for 5 consecutive days. Method failure was reported with 3 mg/day ethinyl estradiol and 25-30 mg/day diethylstilbestrol. No pregnancies were reported at 5 mg/day ethinyl estradiol and 50 mg/day diethylstilbestrol. Kuchera reported on 1000 cases with no pregnancies following treatment with 50 mg diethylstilbestrol administered within 72 hours of unprotected coitus (for a pregnancy rate of 2.5/1000). Other estrogens have been used successfully as postcoital contraceptive agents. Use of conjugated equine estrogens administered orally or intravenously within 72 hours of exposure prevented pregnancy. Dienestrol and dienestrol combined with ethynodiol acetate (progestogen) prevented pregnancy. Depot estradiol administered to 12 patients resulted in 2 ectopic pregnancies. Slow release of this estrogen could account for its high failure rate, although results suggest an effect on zygote transport. It is concluded that the best protection against pregnancy will be obtained by administering estrogen as soon as possible after coitus (preferably within 24 hours, no later than 72 and continued for 5 consecutive days).     

Plasma estrogens in postmenopausal women

The concentration of plasma estrone and estradiol was measured in different groups of postmenopausal women; including physiologic menopause, castration menopause, and those who in addition to menopause had diabetes, hypertension, or cardiac disease. The mean values for estrone were 41 pg. per milliliter and for estradiol 13 pg. per milliliter. There was no statistical difference in the levels of plasma estrogen in all groups of postmenopausal women studied. In 3 individuals, studies of estrogens in ovarian vein blood suggested a nonovarian origin of estrogen.     

Antioxidant properties of estrogens

The author expounded present state of knowledge concerning antioxidant properties of estrogens. Estradiol, apart from its main hormonal effect, probably displays two mechanisms of antioxidant action. One of them results from hydroxyphenolic structure of their molecule. Estradiol may donate hydrogen atoms from its phenolic hydroxyl group to lipid peroxyradicals what results in the termination of the chain reactions of cell membrane phospholipides, which are the key reactions in cell damage. Estradiol also inhibits oxidative modification of LDL lipoprotein which plays the main role in atherogenesis. The other mechanism of antioxidative action of estradiol is probably associated with its stimulatory effect on natural cellular antioxidant enzymes. Data on this subject are scarce and controversial. The mechanisms of antioxidant action of estrogens require further investigation.