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Oral contraceptives linked to gradual bone reduction in some users
Scholes D. J Clin Endocrinol Metab. 2011;doi:10.1210/jc.2010-3027.
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Adolescent girls and young women who use oral contraceptives may be at an increased risk for gradual reductions in bone mineral density, researchers found.
Delia Scholes, PhD, and colleagues enrolled 301 girls aged 14 to 18 years and 305 women aged 19 to 30 years for a prospective cohort study. The cohort included 389 adolescents and young women, who were using oral contraceptives in the form of 20-mcg to 25-mcg doses or 30-mcg to 35-mcg doses of ethinyl estradiol, and 217 nonusers. The researchers measured changes in BMD every 6 months for 2 to 3 years.
After 2 years, adjusted mean percentage gains in BMD were significantly smaller at the spine and whole body sites among adolescents using 30-mcg to 35-mcg oral contraceptive doses compared with nonusers (1.32% vs. 2.26% and 1.45% vs. 2.03%, respectively). In contrast, the BMD of adolescents using lower doses did not differ from nonusers. During the same period, the researchers also noted no disparities between users and nonusers of oral contraceptives among older women.
During the study period, 172 oral contraceptive users discontinued treatment. Adolescents who discontinued either dose experienced considerably smaller gains in BMD at the spine compared with nonusers, with those using higher doses experiencing a more pronounced difference after 1 year (0.51% vs. 1.72%). Young women who discontinued either dose of oral contraceptive also had smaller gains or larger losses in BMD compared with nonusers. After 1 year, those who discontinued use of the 30-mcg to 35-mcg doses lost 0.92% BMD, and those who discontinued lower doses lost 1.32% BMD; nonusers gained 0.27% BMD. These trends persisted at 2 years for both adolescents and young women, according to the researchers.
“The teen years are when women most actively gain bone, so we thought it was important to look at that age group,” Scholes, of the Group Health Research Institute in Seattle, said 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 dose.”
Disclosure: The researchers report no relevant financial disclosures.
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