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 mug ethinyl estradiol/100 mug 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 mug ethinyl estradiol/100 mug levonorgestrel.