| Abstract: | Many publications have been dedicated to the mode of action, efficacy, and secondary effects of oral contraceptives (OCs). Healthy OC users neither accept side effects nor find them acceptable. In most, the level of effectiveness and the incidence of side effects are proportional to the total dose of steroids in the OC combination, the balance between the estrogen and progestin content, and the specific properties of the compounds. Cardiovascular events in OC users were first attributed to the ethinyl estradiol dose and, as a first step, the estrogen dose has been reduced in OCs produced since the 1970s. Next, the vascular risk has been correlated with changes in the lipid profile. Progestins with androgenic properties have been incriminated in unexpected vascular events because of their adverse effect on the lipid profile. In pursuit of minimizing these secondary effects and to favorably change lipid patterns, some new progestins without androgenic properties have been developed and are available in Europe. These new compounds, third generation progestins, are derived from levonorgestrel. These progestins belong to the gonane category and, because of their molecular structure, are capable of attaching themselves to the androgen receptor. They include gestodene, desogestrel, and norgestimate. The study of changes in the pattern of protein markers of the sex hormone binding globulin (SHBG) suggests very weak biological androgen activity when these progestins are administered with ethinyl estradiol. Likewise, the anti-estrogenic action of these progestins which have lost their partial androgenic effect is reduced. When these progestins are administered with the ethinyl estradiol, they do not obstruct the estrogenic effect on the level of protein markers, e.g., SHBG and high density lipoprotein. Although this effect is considered beneficial, the reduced estrogenic activity on antithrombin III, triglycerides, and perhaps target tissues may be considered a non-negligible disadvantage of the third generation progestins in the most recent OCs. |
