Bone mineral density and use of depot medroxyprogesterone acetate (DMPA), norethisterone enanthate (NET-EN) and combined oral contraceptives
Date
2010-09-28
Authors
Beksinska, Malgorzata Elzbieta
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Abstract
Many studies have shown a negative effect of depot-medroxyprogesterone acetate
(DMPA) hormonal contraception on bone mineral density (BMD) in women. There is
limited information on the effect of norethisterone enanthate (NET-EN) on BMD and
the effect of combined oral contraceptives (COCs) on BMD is inconclusive, however
emerging evidence is showing that low-dose COCs maybe detrimental to BMD in young
women. The aim of this research was to evaluate, in a 5-year follow-up study, the
possible effect of DMPA, NET-EN and COCs on BMD among young (15-19 years) and
older (40-49 years) South African women.
Method: This prospective study was conducted at the Commercial City Family Planning
clinic in Durban, South Africa between 2000 and 2007. In the adolescent group women
with no history of hormonal contraception who were initiating use of DMPA (n=115),
NET-EN (n=115) or COCs (n=116) and 144 nonuser controls were recruited. In the older
group, one hundred and twenty seven users of DMPA, 102 NET-EN users and 106 COC
users of at least one year were compared to 161 nonuser controls. BMD was measured at
the distal radius and midshaft of the ulna using dual x-ray absorptiometry. In the crosssectional
component of the study conducted at the end of the longitudinal phase, BMD
was measured at the hip, spine and femoral neck in a sub-group of 96 of the younger
women.
Results: In the longitudinal study of adolescents, BMD increased in all four groups
during follow-up (p<.001). There was evidence for lower BMD increases per annum in NET-EN (p=.050) and COC (p=.010) users compared to nonusers but no difference
between DMPA and nonusers (p=.76). In 14 NET-EN discontinuers, an overall reduction
of 0.61% per year BMD was followed, upon cessation, by an increase of 0.69% per year
(p=.066). The cross-sectional sub-study found that young women in the injectables-only
user group had lower BMDs compared to the non-user group after adjusting for BMI at
the spine (p=0.042), hip (p=0.025), and femoral neck (p=0.023). The mixed
COC/injectable user group BMD values were lower than controls; however, they were
not significant at any of the three sites.
In the older women, there was no significant difference in radius BMD between the
contraceptive user groups and the non-user controls (p=.26) with and without adjustment
for age at baseline, or after two and a half years of follow-up (p=0.52).
Conclusion: This study suggests that BMD increases in adolescents may be less in NETEN
and COC users; however, recovery of BMD in NET-EN users was found in the small
sample of adolescents followed post-discontinuation. The cross-sectional sub-study
showed similar findings in long-term injectable users, but not when women had mixed
injectable and COC use. There was no evidence that long-term use of DMPA, NET-EN
and COCs affected BMD in the older women.
Description
PhD, Faculty of Health Sciences, University of the Witwatersrand
Keywords
bone density, oral contraceptives