[Low-dose oral contraception and bone density]

Abstract

Oral contraceptives (OC) with 20 or 30 mcg Ethinyl-Estradiol (EE) inhibit bone remodeling in all age groups investigated until today as far as the biochemical parameters are considered. In perimenopausal women, OC with 20 or 30 mcg EE reduce the decrease in bone density and may, depending on the starting point, induce an increase in bone density. OC with 20 mcg EE might impede the formation of a physiological peak bone mass in very young women (probably women less than 20 years of age) by a reduction of bone metabolism. This possibility provoked a certain insecurity. However, it should not lead to the consequence that a safe contraceptive method is refused to young women. Unfortunately, there is still a lack of reliable studies allowing a final statement on the effect of low-dose OC on bone density in teenagers. Such studies are urgently needed so that we are able to guarantee in very young women that a reasonable contraception has not to be payed by a long-term risk for the skeletal health. The administration of a progestagen-only pill might be an alternative method for contraception in adolescence. A preparation containing 30 mcg of Levonorgestrel, nearly out of use today, could be of particular interest. A British study (20) has shown that during regular peroral administration of 30 mcg Leveonorgestrel per day, mean serum estradiol concentration decreased only slightly, from 653 to 500 pmol/l. This Estradiol concentration should still allow a normal bone metabolism and therefore a normal formation of the peak bone mass. However, the data actually available do not point convincingly to the conclusion that OC with 20 mcg EE or less might result in an insufficient estrogen concentration for normal bone metabolism. To reach peak bone mass, other factors than estrogens only are needed, such as Calcium, Vitamin D and physical activity.