Bone biochemical markers in adolescent girls using either depot medroxyprogesterone acetate or an oral contraceptive

Study objective To examine the relationship between biochemical markers of bone metabolism and hormonal contraception in adolescents. Design A prospective, observational design. Setting The study was conducted in four adolescent health clinics in a large metropolitan area. Participants The study population comprised healthy, postmenarcheal adolescent girls aged 12–18 initiating either medroxyprogesterone acetate (n = 53) or an oral contraceptive (OC) containing 20 μg ethinyl estradiol/100 μg levonorgestrel (n = 165) and those using no hormonal contraception (n = 152). Interventions None. Main outcome measures Serum bone specific alkaline phosphatase (BSAP), urinary deoxypyridinoline (DPD), and bone mineral density (BMD) at baseline and 12 months. Results At 12 month follow-up, serum BSAP levels were significantly higher (P< 0.05) in the control group (40.4 U/L ± 1.03 SE), than in the DMPA group (35.2 U/L ± 1.05 SE) and the OC group (35.5 U/L ± 1.03 SE). There was a trend in urinary DPD levels to be higher (P = 0.08) in the control group (9.9 nmol/mmol Cr ± 1.03 SE) than in the DMPA group (9.1 ± 1.05 SE) and the OC group (8.9 ± 1.03 SE). No relationship was found between the biochemical markers and BMD at the lumbar spine or the femoral neck. Conclusions Over 12 months, there was evidence of increased bone formation and resorption in the control group when compared to that in the DMPA and OC groups. This finding may indicate a suppression of bone metabolism in girls using DMPA or an OC containing 20 μg ethinyl estradiol/100 μg levonorgestrel.