title: Cortical microstructure and estimated bone strength in young amenorrheic athletes, eumenorrheic athletes and non-athletes.
abstract: BACKGROUND
  Lower bone density in young amenorrheic athletes (AA) compared to eumenorrheic athletes (EA) and non-athletes may increase fracture risk during a critical time of bone accrual. Finite element analysis (FEA) is a unique tool to estimate bone strength in vivo, and the contribution of cortical microstructure to bone strength in young athletes is not well understood.
  
  
  OBJECTIVE
  We hypothesized that FEA-estimated stiffness and failure load are impaired in AA at the distal radius and tibia compared to EA and non-athletes despite weight-bearing exercise.
  
  
  METHODS
  Cross-sectional study; Clinical Research Center
  
  
  METHODS
  34 female endurance athletes involved in weight-bearing sports (17 AA, 17 EA) and 16 non-athletes (14-21 years) of comparable age, maturity and BMI OUTCOME MEASURES: We used HR-pQCT images to assess cortical microarchitecture and FEA to estimate bone stiffness and failure load.
  
  
  RESULTS
  Cortical perimeter, porosity and trabecular area at the weight-bearing tibia were greater in both groups of athletes than non-athletes, whereas the ratio (%) of cortical to total area was lowest in AA. Despite greater cortical porosity in EA, estimated tibial stiffness and failure load was higher than in non-athletes. However, this advantage was lost in AA. At the non-weight-bearing radius, failure load and stiffness were lower in AA than non-athletes. After controlling for lean mass and menarchal age, athletic status accounted for 5-9% of the variability in stiffness and failure load, menarchal age for 8-23%, and lean mass for 12-37%.
  
  
  CONCLUSIONS
  AA have lower FEA-estimated bone strength at the distal radius than non-athletes, and lose the advantage of weight-bearing exercise seen in EA at the distal tibia.
authors.affiliation: Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA. keackerman@partners.org
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Ackerman
authors.forename: Melissa
authors.initials: M
authors.lastname: Putman
authors.forename: Gabriela
authors.initials: G
authors.lastname: Guereca
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Taylor
authors.forename: Lisa
authors.initials: L
authors.lastname: Pierce
authors.forename: David B
authors.initials: DB
authors.lastname: Herzog
authors.forename: Anne
authors.initials: A
authors.lastname: Klibanski
authors.forename: Mary
authors.initials: M
authors.lastname: Bouxsein
authors.forename: Madhusmita
authors.initials: M
authors.lastname: Misra
mesh_terms: D000293:Adolescent; D000568:Amenorrhea / Q000503:physiopathology*; D001823:Body Composition; D015519:Bone Density; D001842:Bone and Bones / Q000502:physiology* / Q000648:ultrastructure*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008598:Menstruation; D015999:Multivariate Analysis; D013177:Sports; D014057:Tomography, X-Ray Computed