Steroid hormone contraception and bone mineral density: a cross-sectional study in an international population. The WHO Study of Hormonal Contraception and Bone Health.

Objective: To evaluate relationships between bone mineral density and use of steroid hormonal contraceptives.

Methods: This was a multicenter cross-sectional study in seven centers in three regions of the developing world from April 1994 to June 1997. Women 30-34 years old attending family planning clinics, with at least 24 months of lifetime use of combined oral contraceptives (OC), depot-medroxyprogesterone acetate (DMPA), or levonorgestrel implants, or no or only short-term (less than 6 months) use of steroid hormonal contraceptives, had bone mineral density (BMD) measured at the distal radius and the midshaft of the ulna using single-photon x-ray absorptiometry.

Results: In the study, 2474 women were examined. For OC use, adjusted mean BMD was significantly higher in short-term, current users compared with women who never used hormonal contraceptives. For DMPA and levonorgestrel implants, adjusted mean BMD was statistically significantly lower in short-term current users compared with those who never used hormonal contraceptives. For all three hormonal methods, there were no significant differences in BMD between past users of hormonal contraceptives and never users, even among those who had used the methods for 4 or more years. The magnitude of changes in BMD was small and less than one standard deviation (SD) from the mean of those who never used steroid contraceptives.

Conclusion: This study suggests that hormonal contraceptive use by young adult women is associated with small changes in BMD that occur early after initiation of use and are reversible.