Despite a pregnancy scare, high school hockey team captain
Sheila C chose to remain sexually active. She vowed, however,
never to tempt fate again and swore off her oral contraceptive
as she often forgets to take her pills. Every three months,
she receives an injection of medroxyprogesterone acetate
(DMPA). Although Sheila gets credit for taking precautions,
she runs the risk of bone loss. The good news for Sheila
and other women on DMPA is that the effects may be reversed
once use of the contraceptive is stopped, according to
a study published in the February issue of Archives
of Pediatrics and Adolescent Medicine.
This finding runs counter to the
FDA black-box warning issued in November 2004, which
states that bone loss from DMPA "may not be completely
reversible." The study followed 170 teens aged 14 to
18 years for 24-36 months. At the outset of the study,
80 girls were using DMPA, while 90 had never been exposed
to the compound. During the course of the study, 61
teens stopped using DMPA. The girls' hip, spine and
whole body bone mineral density (BMD) were measured
every six months.
HIP
TO BMD CHANGE
The hip and spine BMD measurements of those receiving
the contraceptive declined significantly over the course
of the study when compared to non-users. The mean annualized
change at the hip was -1.81% and -0.19% for users and
non-users respectively. Similarly, the mean changes
for the spine were -0.97% for the DMPA group and 1.32%
for those who weren't taking it. Even more frightening
is the fact that those who began using the contraceptive
during the study experienced a more rapid BMD decrease
than those who had been using DMPA at the outset.
There was no significant difference
in the changes observed in whole body BMD between subjects.
But the really good news came when BMD data on folks
who quit using DMPA was studied. Compared to the non-users,
those who quit piled on BMD at the hip (-0.19% vs 1.34%),
spine (1.32% vs 2.86%) and whole body (0.88% vs 3.56%).
The study was limited by a lack
of BMD data prior to DMPA use in the participants who
were practising contraception at the outset. Nonetheless,
the findings of the study "are reassuring for those
concerned about future risk of fractures," commented
lead author Dr Delia Scholes of the Group Health Cooperative's
Center for Health Studies in Seattle. "This information
can be useful in helping young women balance the need
to avoid unintended pregnancies with the need to build
strong bones," she told Reuters.
This study adds to a growing list
of reports that link the injectable contraceptive with
bone loss. According to Health Canada, young women who
are still gaining bone represent a particular concern.
Thankfully, the effects appear to be reversible.
Arch Pediatr Adolesc Med Feb
2005;159:139-44
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