title: The effect of oral contraceptives on bone mass and stress fractures in female runners.
abstract: OBJECTIVE
  To determine the effect of oral contraceptives (OC) on bone mass and stress fracture incidence in young female distance runners.
  
  
  METHODS
  One hundred fifty competitive female runners ages 18-26 yr were randomly assigned to OC (30 microg of ethinyl estradiol and 0.3 mg of norgestrel) or control (no intervention) for 2 yr. Bone mineral density (BMD) and content (BMC) were measured yearly by dual x-ray absorptiometry. Stress fractures were confirmed by x-ray, magnetic resonance imaging, or bone scan.
  
  
  RESULTS
  Randomization to OC was unrelated to changes in BMD or BMC in oligo/amenorrheic (N=50) or eumenorrheic runners (N=100). However, treatment-received analyses (which considered actual OC use) showed that oligo/amenorrheic runners who used OC gained about 1% per year in spine BMD (P<0.005) and whole-body BMC (P<0.005), amounts similar to those for runners who regained periods spontaneously and significantly greater than those for runners who remained oligo/amenorrheic (P<0.05). Dietary calcium intake and weight gain independently predicted bone mass gains in oligo/amenorrheic runners. Randomization to OC was not significantly related to stress fracture incidence, but the direction of the effect was protective in both menstrual groups (hazard ratio [95% CI]: 0.57 [0.18, 1.83]), and the effect became stronger in treatment-received analyses. The trial's statistical power was reduced by higher-than-anticipated noncompliance.
  
  
  CONCLUSIONS
  OC may reduce the risk for stress fractures in female runners, but our data are inconclusive. Oligo/amenorrheic athletes with low bone mass should be advised to increase dietary calcium and take steps to resume normal menses, including weight gain; they may benefit from OC, but the evidence is inconclusive.
authors.affiliation: Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA 94305, and Clinical Research Center, Helen Hayes Hospital, West Haverstraw, NY, USA. kcobb@stanford.edu
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Cobb
authors.forename: Laura K
authors.initials: LK
authors.lastname: Bachrach
authors.forename: Maryfran
authors.initials: M
authors.lastname: Sowers
authors.forename: Jeri
authors.initials: J
authors.lastname: Nieves
authors.forename: Gail A
authors.initials: GA
authors.lastname: Greendale
authors.forename: Kyla K
authors.initials: KK
authors.lastname: Kent
authors.forename: Byron W
authors.initials: BW
authors.lastname: Brown
authors.forename: Kate
authors.initials: K
authors.lastname: Pettit
authors.forename: Diane M
authors.initials: DM
authors.lastname: Harper
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Kelsey
mesh_terms: D000293:Adolescent; D000328:Adult; D000568:Amenorrhea / Q000150:complications / Q000188:drug therapy; D015519:Bone Density / Q000187:drug effects*; D003278:Contraceptives, Oral, Hormonal / Q000009:adverse effects / Q000627:therapeutic use*; D002149:Energy Intake / Q000502:physiology; D005260:Female; D015775:Fractures, Stress / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D006801:Humans; D009839:Oligomenorrhea / Q000150:complications / Q000188:drug therapy; D018570:Risk Assessment; D012420:Running / Q000293:injuries* / Q000502:physiology; D014481:United States / Q000453:epidemiology