Previous studies had shown that women who use DMPA experience a loss of bone mineral density during the time they are using the contraceptive. Because women are developing a large amount of their bone mass from ages 15 to 19, researchers were concerned that DMPA use might place adolescents at higher risk for bone fracture or osteoporosis later in life.

"This study shows that after adolescents stop using DMPA, their bone density can increase to levels comparable to those of other women in their age group," said Duane Alexander, M.D., Director of the National Institute of Child Health and Human Development (NICHD).

The researchers measured hip, spine, and whole body bone mineral densities in 170 healthy female adolescents ages 14 to 18. Of these, 80 had used DMPA, and 90 had not. Some of the 90 who had not used DMPA had used other forms of contraception, including oral contraceptives. Some oral contraceptives contain a combination of the hormones estrogen and progestin, some contain only progestin. It is not known whether oral contraceptive use affects bone mineral density. NICHD is currently supporting a study to address this issue.

The researchers measured the participants' bone mineral densities when the study began, and every six months thereafter for the next two to three years. During the course of the study, 61 women stopped using the contraceptive.

The researchers found that DMPA users had a greater reduction in bone density findings than did non-users. Dr. Scholes explained that these bone density losses seen among the DMPA users occurred at a pace similar to those experienced by women progressing through menopause.

Once the women stopped using DMPA, they experienced significant gains in bone density. The study authors wrote that the increase in bone mineral density after discontinuation of DMPA is similar to the bone mineral density increase after a woman stops breast feeding.; Source: NIH/National Institute of Child Health and Human Development