Objective: To compare changes in bone mineral density (BMD) during 48 months between first-time depot medroxyprogesterone acetate (MPA) users, during use and after discontinuation, to controls.
Design: Longitudinal study.
Setting: Academic community.
Patient(s): Women 18-35 years, newly initiating depot MPA (n = 178) and controls (n = 145) not using hormonal contraception.
Main outcome measure(s): The BMD of the hip and spine, measured at 3-month intervals, by dual energy roentgen absorptiometry.
Results: Hip and spine BMD declined during 48 months of depot MPA use by 7.7% +/- 0.11% (mean +/- SE) and 6.4% +/- 0.36%, respectively. The BMD of controls declined <or=1.6% +/- 0.30%. Hip and spine BMD loss slowed to <0.6% after 48 months of depot MPA use. After discontinuation, BMD increased from 0.3% to 2.0% per year depending on length of depot MPA use and bone site. The longest depot MPA users remained 4.7% and 2.9% lower than hip and spine baseline values, respectively, 18 months after discontinuation.
Conclusion(s): Depot MPA-related BMD loss is substantial but occurs mostly during the first 2 years of DMPA use. Therefore, longer use may not substantially increase the risk of osteoporosis. The prolonged recovery time suggests the need to consider timing of use in relation to menopause or other factors that may impede bone remodeling.