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  • Title: [Oral contraception: disadvantages of estrogen reduction].
    Author: Denis C.
    Journal: Contracept Fertil Sex (Paris); 1993 Jun; 21(6):481-8. PubMed ID: 12318238.
    Abstract:
    New oral contraceptives (OCs) include formulations with reduced estrogen and progestin doses intended to reduce cardiovascular risk and triphasic pills that allow maximum steroid concentrations to coincide with the luteinizing hormone LH surge. The risk of administering low steroid doses is that the antigonadotropic effect will be insufficient to inhibit endogenous estrogen secretion in some women. Individual receptivity to sex steroids is known to be highly variable. Incomplete ovarian inhibition poses risks over the short and long terms of functional ovarian cysts and loss of the protective effects of higher dosed pills against ovarian and endometrial cancers and benign breast disease. It is impossible to compare the different OC formulations because no truly comparative prospective studies have yet been done, the number of subjects in existing trials has been small, and the methods of measuring the different hormones and overall evaluation criteria have differed. Follow-up of subjects is variable, usually ranging from 1 to 12 months, but hormone levels vary at different durations of usage. Most studies have contained no statistical data. Available studies indicate that low-dose formulations in general provide a sufficient ovarian blockage. The hypothalamopituitary axis is not as strongly inhibited except by OCs containing 50 mcg of ethinyl estradiol (EE). Formulations containing the 3rd generation progestins have the strongest inhibiting effect. When EE doses decline from 30 to 20 mcg, the suppressive effect on ovarian activity usually persists, but 20 mcg of EE is not enough for some women. Unfortunately, no studies have examined the efficacy of a formulation with 30 mcg of EE in women insufficiently responding to 20 mcg. Results concerning the effect of 20 mcg formulations on the hypothalamopituitary axis are contradictory; a crossover, double-blind, comparative study on a sufficient number of women will be required to evaluate definitively the effect of reduction from 30 to 20 mcg. From a practical standpoint, it is more interesting to compare clinical tolerance to the 30 and 20 mcg formulations. Available studies on breast effects and cycle control, the incidence of ovarian cysts, metabolic effects, and the persistence of other beneficial effects of higher-dosed OCs suggest that the disadvantages of reducing estrogen doses are minor. The most important is the reduced protection against ovarian cysts observed in 2nd generation formulations. Because of the strong inhibition of ovarian activity and the powerful progestomimetic activity of the 3rd generation progestins, it is probable that ongoing studies will demonstrate that the beneficial effects of higher-dosed OCs persist. Cycle disturbances have not been observed with formulations containing at least 20 mcg of EE. Until definitive results become available, however, it is recommended that low-dose OCs be avoided in women requiring complete blockage of ovarian activity.
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