Objectives To compare the effect of a low-dose oral contraceptive (OC) containing 30 μg ethinyloestradiol (EE) with that of an ultra-low-dose OC containing 15 μg EE on bone turnover and BMD in healthy adolescent women and, in addition, to ascertain the influence of body mass index (BMI) and exercise on these indices of bone metabolism.

Methods We recruited to the study 92 healthy girls aged between 16 and 19. They were divided into three groups. Participants in the first two groups used an OC with either 15 or 30 μg ethinyloestradiol (EE), whereas those in the third group used no hormonal contraception. Bone mineral density (BMD) and bone turnover markers were measured before and after 12 months of treatment.

Results The BMD values of the total hip in females using the OC containing 30 μg EE was 0.912 g/cm² at baseline and 0.918 g/cm² after one year; in females using the OC containing 15 μg EE the corresponding values were 0.888 g/cm² and 0.895 g/cm² whereas in females who used no contraception BMD values were 0.942 g/cm² and 0.949 g/cm², respectively. The changes were statistically insignificant. Levels of osteocalcin and CTX had decreased after one year in all groups, but not statistically significantly so.

Conclusion Low dose and ultra-low dose oral contraceptives did not significantly differ in their effects on bone mineral density or bone turnover markers in adolescent girls aged 16-19.