Hartard M et al. (2006) Detrimental effect of oral contraceptives on parameters of bone mass and geometry in a cohort of 248 young women. Bone [doi:10.1016/j.bone.2006.08.001]

Previous studies raised concerns that oral contraceptives, which suppress endogenous estrogen production, might impair bone mineralization and increase fracture risk in young women. Hartard and colleagues accordingly assessed the effect of low-dose, monophasic, oral contraceptives on BMD in a cross-sectional study that involved 248 healthy women aged 18–24 years.

Examinations included measurement of volumetric BMD, bone mineral content (BMC) and bone geometry of the tibia by peripheral quantitative CT, and measurement of areal BMD of the femoral neck and lumbar spine by dual-energy X-ray absorptiometry. There was a correlation between contraceptive use and bone mass at all sites. In the 201 women who had ever used oral contraceptives, femoral-neck BMD, tibial cross-sectional area and tibial total BMC were significantly lower (P <0.005, P <0.01 and P <0.05, respectively) than in the 47 women who had never taken oral contraceptives. Further differences were observed that depended on the duration and time of initiation of contraceptive use. Women who started oral contraceptives within 3 years after menarche and had taken them for >2 years had 10% lower femoral-neck areal BMD, 7% lower distal-tibial BMC and 6% lower total BMC at the tibial shaft, compared with women who had never taken oral contraceptives.

The authors conclude that oral contraceptive use can potentially harm the skeletal development of young women; they call for long-term studies to investigate the pathogenic mechanism that underlies this finding.