Oral contraceptive use during adolescence may reduce bone density later

Although overall impact on bone is small and depends largely on age and dose, data suggest that by about 2 years of use, teens who use oral contraceptives (OCs) show about 1% less gain in bone mineral density (BMD) than teens who do not use the pills, and they show smaller gains in bone density even after they stop using the pills.

Researchers in Seattle, Washington, conducted a prospective cohort study involving 606 women between the ages of 14 and 30 years. About 50% of the participants were between 14 and 18 years of age, while the remainder were between 19 and 30 years of age. Of the OC users in the study, about half used OCs containing 30 µg to 35 µg ethinyl estradiol (EE), while the remainder used OCs containing less than 30 µg EE; 172 of the women discontinued use of OCs. The researchers measured hip, spine, and whole-body bone densities.

After 2 years, they found that the teens using 30 µg to 35 µg EE OCs, but not those using less than 30 µg EE OCs, had significantly smaller adjusted mean percentage BMD gains at the spine and whole body (95% CI for between-group differences; 1.32% vs 2.26% and 1.45% vs 2.03%, respectively), compared with the nonusers.

This information may be important because a woman's risk for fractures later in life depends partially on the bone she amasses in her teens and twenties, and women in this age group are the highest users of OCs.

Scholes D, Hubbard RA, Ichikawa LE, et al. Oral contraceptive use and bone density change in adolescent and young adult women: a prospective study of age, hormone dose, and discontinuation. J Clin Endocrinol Metab. July 13, 2011. [Epub ahead of print.]