title: Bone mineral density in a cohort of adolescents during use of norethisterone enanthate, depot-medroxyprogesterone acetate or combined oral contraceptives and after discontinuation of norethisterone enanthate.
abstract: BACKGROUND
  Depot medroxyprogesterone acetate (DMPA), norethisterone enanthate (NET-EN) and combined oral contraceptives (COCs) have been shown to have a negative effect on bone mineral density (BMD) in adolescents. The aim of this study was to investigate BMD in 15- to 19-year-old new users of DMPA, NET-EN and COCs.
  
  
  METHODS
  This 5-year longitudinal study followed up new users of DMPA (n=115), NET-EN (n=115) and COCs (n=116) and 144 nonuser controls. BMD was measured at the distal radius using dual-energy X-ray absorptiometry.
  
  
  RESULTS
  BMD increased in all groups (annual percent increase: nonusers, 1.49%; DMPA, 1.39%; NET-EN, 1.03%; COCs, 0.84%) 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).
  
  
  CONCLUSIONS
  This study suggests that BMD increases in adolescents may be less in NET-EN and COC users; however, recovery of BMD in NET-EN users was found in the small sample of adolescents followed post-discontinuation.
authors.affiliation: Department of Obstetrics and Gynaecology, Reproductive Health and HIV Research Unit, University of the Witwatersrand, Mayville, South Africa.
authors.forename: Mags E
authors.initials: ME
authors.lastname: Beksinska
authors.forename: Immo
authors.initials: I
authors.lastname: Kleinschmidt
authors.forename: Jenni A
authors.initials: JA
authors.lastname: Smit
authors.forename: Timothy M M
authors.initials: TM
authors.lastname: Farley