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.