Study objective: To examine bone mineral density (BMD) on a semi-annual basis among control subjects and adolescent females receiving depot medroxyprogesterone acetate (DMPA) injection or oral contraceptives.
Design: Non-randomized prospective study.
Setting: Teenage pregnancy prevention intervention clinic.
Participants: Adolescent females who were new users of DMPA injection (N=58, age 12-21) or the oral contraceptive pill (N=71, age 11-19) and normal menstruating girls (N=19, age 15-18).
Interventions: Baseline and 6-monthly measures of lumbar vertebral BMD using dual-energy X-ray absorptiometry over a 2-year period.
Main outcome measures: comparison of percent change on BMD over time between DMPA users, pill users, and normal menstruating girls.
Results: There was no difference on group characteristics at baseline except for the ethnicity between the controls and the DMPA group. There was a statistically significant decrease in BMD between DMPA users and controls at 6 months (-3.02% change, P=0.014) 12 months (-3.38% change, P=0.001) 18 months (-4.81% change, P<0.001) and 24 months (-6.81% change, P=0.010). There was no statistical difference between pill users and controls.
Conclusion: There is a relationship between DMPA use and a decrease in BMD compared to normal menstruating controls that seems to persist up to 24 months.