The effect of past use of the injectable contraceptive depot medroxyprogesterone acetate on bone mineral density in normal post-menopausal women

OBJECTIVE Depot medroxyprogesterone acetate (DMPA), an injectable progestogen, is a widely used contraceptive acting primarily by inhibiting secretion of pituitary gonadotrophins, thus producing oestrogen deficiency. Cross-sectional and prospective studies in pre-menopausal women have shown DMPA use to be associated with reduced bone density, but bone density increases following discontinuation of the drug. Because fracture rates are low in premenopausal women, the principal concern arising from the effects of DMPA on bone is that there may be residual osteopenia in former users such that their post-menopausal fracture risk is increased. The present study addresses this question, DESIGN Cross-sectional study of bone density in post-menopausal former users of DPMA and controls, SUBJECTS Three hundred and forty-six normal postmenopausal women, of whom 34 had previously used DMPA, The median age at which DMPA use began was 41 years and the median duration of use was 3.0 years, MEASUREMENTS Bone density was measured in the spine, proximal femur and total body by dual-energy, X-ray absorptiometry. RESULTS There were no significant differences in bone density at any site between the women who had previously used DMPA and the others in the cohort. However, in those who had used DMPA for >2 years there was a trend towards bone densities being lower in the former users, the differences from non-users being 1.6% in the lumbar spine (P = 0.6), 3.1% in the femoral neck (P = 0.4) and 0.5% in the total body (P = 0.8). There was no correlation between bone densities and the duration of DMPA use, the age at discontinuation of DMPA, or the time between DMPA discontinuation and the menopause. CONCLUSIONS Any residual effects of depot medroxyprogesterone acetate use on post-menopausal bone density are small and therefore unlikely to have a substantial impact on fracture risk in the post-menopausal years.