INJECTABLE CONTRACEPTIVES AND BONE ULTRASOUND MEASURES

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DESCRIPTION (provided by applicant): Some studies of largely white populations suggest that users of the injectable progestogen contraceptive (IPC), depot-medroxyprogesterone acetate (DMPA), have lower bone mineral density than nonusers. This has biologic credibility because DMPA use results in decreased levels of estrogen. In one study, the difference in bone mineral density between users and nonusers was concentrated in women aged 18-21 years, among whom peak bone mineral density would not yet have been achieved, but in another study there was no relation of the bone loss to age. An irreversible effect of IPCs on bone would have serious implications for rates of osteoporotic fractures later in Life, particularly for women who used IPCs at young ages. Black (African) and colored (mixed racial descent) women in South Africa have very high rates of long-term IPC use, about 80 percent of which is DMPA and 20 percent norethisterone enanthate. Ultrasound bone measurements of the heel are strongly predictive of fractures. We will conduct a cross-sectional study of heel bone as measured by ultrasound sonometry in relation to IPC use among black and colored premenopausal women aged 18-44 years in greater Cape Town, South Africa. The aim is to assess whether IPCs are associated with lower ultrasound heel bone measurements. We will also assess whether an adverse effect decreases after cessation of use, whether it is concentrated among younger women, and whether it is related to the duration of use in either current or ex-users. Both DMPA and norethisterone enanthate will be assessed. Information on IPC use and other relevant factors (e.g., oral contraceptive use, cigarette smoking, body mass index, alcohol use, physical activity, lactation, milk intake, and reproductive history) will be obtained through personal interview: height and weight will be measured. The study will assess longer durations of use than any previous study. It should be noted that an effect of IPCs may differ between ethnic groups. Our study will be the first to informatively assess black and colored women whose heel bone measurements differ from each other and/or those of white women. Millions of women worldwide have used IPCs. Given the heavy burden of osteoporotic fractures in elderly women, it is of public health importance to determine whether IPCs have an adverse effect on bone.