title: Bone mineral density in adolescents using norethisterone enanthate, depot-medroxyprogesterone acetate or combined oral contraceptives for contraception.
abstract: OBJECTIVE
  Most studies have shown a negative effect of depot-medroxyprogesterone acetate (DMPA) on the bone mineral density (BMD) of adolescents. There is no information available on the effect of norethisterone enanthate (NET-EN) on BMD in adolescents and the effect of combined oral contraceptives (COCs) on adolescent BMD is inconclusive. The aim of this longitudinal study was to investigate BMD in adolescent (aged 15-19 years) new users of hormonal contraception (DMPA, NET-EN and COCs).
  
  
  METHODS
  New users of DMPA (n=115), NET-EN (n=115), COCs (n=116) and 144 nonuser controls were recruited. BMD was measured at the distal radius and midshaft of the ulna using dual X-ray absorptiometry.
  
  
  RESULTS
  In total, 275 women were included in this interim analysis and total follow-up time was 553 person-years. There was no significant difference in radius BMD between users of different contraceptive methods at baseline (p=.40). Overall, an increase in radius BMD of 0.00522 per person-year was observed. This result was similar when adjusting for BMI in the random effects regression model (p=.88). The regression model showed that BMI was significantly associated with radius BMD, with each unit increase in BMI corresponding to an increase of 0.0029 g/cm2 in BMD (95% CI 0.0023 to 0.0036, p<.001). Interaction between contraceptive method and follow-up time adjusted for BMI was not significant (p=.07). The increase in BMD for NET-EN users of 0.0013 g/cm2 per person-year (95% CI -0.0017 to 0.0043) was significantly lower than that of nonusers (p=.017). For DMPA and COC users, the increase in BMD was not significantly different compared to the nonusers. This study suggests that NET-EN users had lower increase in BMD over time compared to the other user groups.
authors.affiliation: Reproductive Health and HIV Research Unit, Department of Obstetrics and Gynaecology, University of the Witwatersrand, Mayville 4091, South Africa. m.beksinska@rhru.co.za
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
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D015519:Bone Density / Q000187:drug effects*; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage*; D003692:Delayed-Action Preparations; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage*; D009640:Norethindrone / Q000008:administration & dosage / Q000031:analogs & derivatives*; D011795:Surveys and Questionnaires
chemical_list: D003277:Contraceptives, Oral, Combined; D003692:Delayed-Action Preparations; D017258:Medroxyprogesterone Acetate; C024319:norethindrone enanthate; D009640:Norethindrone