Effects of depot medroxyprogesterone acetate and 20-microgram oral contraceptives on bone mineral density

Hormonal contraceptives may adversely affect bone mineral density. However, racial differences and the reversibility of these changes are poorly understood. This study measured bone mineral density changes during hormonal contraceptive use and after discontinuation in a triethnic population.

Bone mineral density was measured every 6 months for up to 3 years in 703 white, African-American, and Hispanic women using oral contraceptives (OCPs), depot medroxyprogesterone acetate (DMPA), or nonhormonal contraceptives, and in 68 DMPA discontinuers for up to 2 additional years. Mixed-model regression analyses were used to estimate the percentage change in bone mineral density for each contraceptive method.

Over 3 years, DMPA and OCP users lost more bone mineral density than did nonhormonal contraceptive users (-3.7% and -0.5% compared with +1.9% at lumbar spine, and -5.2% and -1.3% compared with +0.6% at femoral neck, respectively). No differences were observed by race in bone mineral density changes that resulted from DMPA or OCP use. However, DMPA users aged 16-24 years lost more bone mineral density at the spine (4.2% compared with 3.2%, P=.006) and femoral neck (6.0% compared with 4.2%, P=.001) than those aged 25-33 years. After DMPA discontinuation, women who selected nonhormonal contraceptives gained bone mineral density (+4.9% at spine, +3.2% at femoral neck), whereas those who selected OCP recovered spinal (+2.3%) but not femoral neck bone mineral density (-0.7%).

Use of very-low-dose OCPs may result in a small amount of bone loss. Use of DMPA results in greater bone loss, but this is largely reversible at the spine. Use of very-low-dose OCPs after DMPA discontinuation may slow bone recovery.