Changes in calcium metabolism and bone mineral density in new users of medroxyprogesterone acetate during the first year of use

Objective: To evaluate calcium metabolism and bone mineral density (BMD) in new users of depot medroxyprogesterone acetate (DMPA) in the first year of use.

Methods: This prospective, non-randomized study, conducted at the University of Campinas, São Paulo, Brazil, was carried out between February 2011 and February 2013. Women aged from 18 to 40 with a body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters) <30 and with no known history of disease or medication use who chose to use DMPA were paired by age (±1 year) and BMI (±1) with women commencing the use of a copper intrauterine device (IUD). The primary outcomes were BMD measured by dual-energy X-ray absorptiometry and calcium metabolism markers; other variables were body composition and lifestyle habits. Repeated measures analysis of variance (ANOVA) and multiple regression analyses were used to evaluate associations.

Results: Twenty-seven women using DMPA and 24 using IUD were evaluated, with a mean age of 29.7 years and 28.6 years, respectively. The DMPA group presented with a 3.6% (P<0.001) loss of lumbar spine BMD, a 2.1% (P=0.100) loss of femoral neck BMD and higher phosphorus (P=0.014) concentrations at 12 months compared to the IUD group. The decreases in BMD were associated with the use of DMPA, while total mass and coffee intake were found to be protective factors.

Conclusion: Changes in calcium metabolism and a decrease in BMD were found in the DMPA group at 12 months.