Gradual bone reduction seen in some oral contraceptive users

Oral contraceptives may reduce a woman’s bone density, according to a study published online in The Journal of Clinical Endocrinology by Group Health Research Institute investigators.

The impact oral contraceptive use had on bone was small and depended upon the woman’s age — as well as the pill’s hormone dose — and did not appear in the study until about 2 years of use. The study size and design allowed researchers to focus on 14- to 18-year-old teenagers and focus on how bone density might change after a woman stops using oral contraceptives.

“The teen years are when women most actively gain bone, so we thought it was important to look at that age group,” lead author Delia Scholes, PhD, stated in a press release. “We found that oral contraceptive use had a small negative impact on bone gain at these ages, but took time to appear, and depended on hormone use.”

Researchers performed a prospective cohort study on 606 women from the ages of 14 to 30 — 301 from the ages of 14 years to 18 years and 305 from the ages of 15 years to 30 years — measuring hip, spine and whole-body bone densities. The cohort consisted of 389 oral contraceptive users and 217 age-similar non-users, with 172 individuals who eventually discontinued their use of oral contraceptives. The researchers reported a 78% rate of 24-month retention, with bone density measurements being taken at the start of the study and every 6 months for 2 years to 3 years.

According to the study abstract, the team found that after 24 months individuals who used higher doses of oral contraceptive displayed around 1% less gain in bone density at both the spine and whole body sites than teens who did not use hormonal contraceptives. Young adult women, users and non-users of oral contraceptives were reportedly found to display no difference in bone density at any site.

“Bone health, especially for long-term users of the pill, may be one of many factors women consider in choosing a contraceptive method that’s right for them,” Scholes stated, adding additional studies — such as investigations into bone changes over a longer span after pill use is discontinued — could help elucidate how oral contraceptive use is related to fracture risk.

Reference:

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. 2011. doi: 10.1210/jc.2010-3027

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