ATLANTA — Impaired bone mass acquisition associated with certain oral contraceptives may be a hidden problem affecting adolescent girls, Dr. Barbara Cromer said at the annual meeting of the North American Society for Pediatric and Adolescent Gynecology.
Preliminary data from a pilot study comparing bone mineral density in adolescent girls using oral contraceptives containing two different levels of estrogen demonstrated an apparent blunting of bone development gains associated with the lower-estrogen pill, said Dr. Cromer of MetroHealth Medical Center in Cleveland.
Of 12 girls aged 12–18 years included in the randomized study, 5 received a combination oral contraceptive with 20 mcg of ethinyl estradiol and 1 mg of norethindrone acetate for 12 months and 7 received one with 35 mcg of ethinyl estradiol and 1 mg norethindrone for the same duration. All the girls underwent BMD testing with dual-energy x-ray absorptiometry at the lumbar spine (L1-L4) and at the femoral neck at baseline at 6 months and 12 months.
At 12 months, the mean percentage of change in bone mass acquisition from baseline in the lower-estrogen group was 1%, compared with 2% in the higher-dose group, Dr. Cromer reported.
A key question is obviously whether the difference is clinically significant, and “it's one that absolutely warrants further investigation,” she said. “If there is clinical significance, we need to think about whether the appropriate dose of ethynyl estradiol for teens may be 35 mcg and whether the trade-off with the risk of VTE—which is relatively small in adolescents—is acceptable.” It also needs to be clarified whether bone mass recovery occurs after cessation of these agents and whether lifestyle factors can override some of the negative bone effects, she said.