title: Differential associations for menopause and age in measures of vitamin K, osteocalcin, and bone density: a cross-sectional exploratory study in healthy volunteers.
abstract: OBJECTIVE
  To distinguish the effects of midlife aging from early postmenopause on vitamin K measures, bone formation biomarkers, and bone density.
  
  
  METHODS
  Cycling older volunteers (CO; 40-52 years, n = 19) were compared to cycling young (CY; 20-30 years, n = 21) and untreated, age-matched women in the early postmenopause years (EPM; 40-52 years, mean years PM = 2.8 +/- 0.5, n = 19). We assessed sex steroids, vitamin status (phylloquinone, 25-hydroxyvitamin D, retinol), osteocalcin (OC), percentage of undercarboxylated osteocalcin (%ucOC), and bone mineral density (BMD) at the spine and hip with dual-energy x-ray absorptiometry.
  
  
  RESULTS
  CO women had similar estradiol and vitamin status as CY women, but lower OC (0.64 +/- 0.04 vs 0.97 +/- 0.08 nmol/L, P = 0.01) and BMD at the total hip (1.0038 +/- 0.032 vs 1.1126 +/- 0.030 g/cm2, P = 0.02). In the two older groups, BMD was similar at all sites, but OC was elevated in the EPM women (1.10 +/- 0.10 vs 0.64 +/- 0.04 nmol/L, EPM vs CO, P = 0.001). Although phylloquinone was highest in the EPM women, %ucOC was also higher when compared with all cycling women (21.9 +/- 1.7% vs 17.4 +/- 0.9%, n = 40; P = 0.02).
  
  
  CONCLUSIONS
  Premenopausal women show reduced BMD despite normal estrogen profiles. %ucOC may be a specific bone marker of the early postmenopause in healthy women.
authors.affiliation: School of Nursing, University of Michigan, Ann Arbor, MI, USA. lukacsj@umich.edu
authors.forename: Jane L
authors.initials: JL
authors.lastname: Lukacs
authors.forename: Sarah
authors.initials: S
authors.lastname: Booth
authors.forename: Michael
authors.initials: M
authors.lastname: Kleerekoper
authors.forename: Rudi
authors.initials: R
authors.lastname: Ansbacher
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Rock
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Reame
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000367:Age Factors; D000375:Aging / Q000097:blood / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008593:Menopause / Q000097:blood / Q000502:physiology*; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood*; D014812:Vitamin K / Q000097:blood*
chemical_list: D015675:Osteocalcin; D014812:Vitamin K