Hormonal Contraceptive Use, Bone Density, and Biochemical Markers of Bone Metabolism in British Army Recruits

Introduction: Hormonal contraceptive use might impair bone health and increase stress fracture risk by decreasing endogenous oestrogen production, a central regulator of bone metabolism. This cross-sectional study investigated bone density and biochemical markers of bone metabolism in women taking hormonal contraceptives on entry to basic military training. Methods: Forty five female British Army recruits had biochemical markers of bone metabolism, areal bone mineral density (aBMD), and tibial speed of sound (tSOS) measured at the start of basic military training. Participants were compared by their method of hormonal contraception: no hormonal contraception (NONE), combined oral contraceptive pill (COCP) users, or depot medroxyprogesterone acetate (DMPA) users (20 ± 2.8 yrs, 1.64 ± 0.63 m, 61.7 ± 6.2 kg). Results: aBMD was not different between groups (p ≥ 0.204), but tSOS was higher in NONE (3%, p = 0.014) when compared with DMPA users. sCTX was higher in NONE (45%, p = 0.037) and DMPA users (90%, p = 0.003) compared with COCP users. P1NP was higher in DMPA users compared with NONE (43%, p = 0.045) and COCP users (127%, p = 0.001), and higher in NONE compared with COCP users (59%, p = 0.014). Bone ALP was higher in DMPA users compared with COCP users (56%, p = 0.044). Conclusions: DMPA use was associated with increased bone turnover, and decreased cortical bone integrity of the tibia. Lower cortical bone integrity in DMPA users was possibly mediated by increased intracortical remodelling, but trabecular bone was not affected by contraceptive use.