Evidence that treatment with monophasic oral contraceptive formulations containing ethinylestradiol plus gestodene reduces bone resorption in young women.

The aim of the study was to evaluate if a pill containing the same dose of the same type of progestin compound (gestodene, GES, 75 microg) but different doses of ethinylestradiol (EE2) (20 or 30 microg) differently influences specific markers of bone resorption (urinary levels of pyridinoline (PYR) and dexoxypyridinoline (D-PYR)). During the 12 months of the study a significant decrease of urinary levels of PYR and D-PYR was found in 2 groups of young post-adolescent women taking the pills with 20 and 30 microg of EE2 in comparison with control women (subjects of the same age group with normal menstrual cycle who did not use contraception). In women taking pills with 20 or 30 microg EE2, the levels of sex hormone-binding globulin (SHBG) significantly increased during treatment in comparison with baseline, whereas in the same time period no changes occurred in control women. These findings suggest that similar to the pill containing 30 microg EE2, the lower dosage of the EE2 pill (20 microg) is also capable of reducing bone resorption. Twenty and 30 microg EE2 pills exert the same biological estrogenic effect. In fact, SHBG levels significantly increased with both pills. However, an additional effect of the progestin compound that could act directly on progestin or estrogen receptors of bone cannot be excluded. Since contraception with a pill containing the lowest estrogen dose is associated with the lowest incidence of side effects, these findings further suggest a pill containing 20 microg EE2 for young post-adolescent women would be the best choice.