title: Relationship between vitamin D, parathyroid hormone, and bone health.
abstract: BACKGROUND
  There is a controversy regarding the definition of vitamin D insufficiency as it relates to bone health.
  
  
  OBJECTIVE
  The objective of the study was to examine the evidence for a threshold value of serum 25-hydroxyvitamin D (25OHD) that defines vitamin D insufficiency as it relates to bone health.
  
  
  METHODS
  This was a cross-sectional analysis of baseline data in 488 elderly Caucasian women, mean age 71 yr, combined with a literature review of 70 studies on the relationship of serum PTH to serum 25OHD.
  
  
  METHODS
  The study was conducted in independent-living women in the midwest United States.
  
  
  METHODS
  The relationship between serum 25OHD, serum PTH, and serum osteocalcin and 24-h urine N-telopeptides was evaluated.
  
  
  RESULTS
  Serum PTH was inversely correlated with serum 25OHD (r = -0.256, P < 0.0005), but no threshold as defined by suppression of serum PTH was found within the serum 25OHD range 6-60 ng/ml (15-150 nmol/liter). However, in contrast, there was a threshold for bone markers, serum osteocalcin and urine N-telopeptides, that increased only below a serum 25OHD of approximately 18 ng/ml (45 nmol/liter). Calcium absorption was not correlated with serum PTH and serum 25OHD, and no threshold was found. A literature review of 70 studies generally showed a threshold for serum PTH with increasing serum 25OHD, but there was no consistency in the threshold level of serum 25OHD that varied from 10 to 50 ng/ml (25-125 nmol/liter).
  
  
  CONCLUSIONS
  Vitamin D insufficiency should be defined as serum 25OHD less than 20 ng/ml (50 nmol/liter) as it relates to bone.
authors.affiliation: Bone Metabolism Unit, Department of Medicine, Creighton University Medical Center, 601 North 30 Street, Suite 6718, Omaha, Nebraska 68131, USA. adarshsai@creighton.edu
authors.forename: A J
authors.initials: AJ
authors.lastname: Sai
authors.forename: R W
authors.initials: RW
authors.lastname: Walters
authors.forename: X
authors.initials: X
authors.lastname: Fang
authors.forename: J C
authors.initials: JC
authors.lastname: Gallagher
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology; D015415:Biomarkers; D001842:Bone and Bones / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D003430:Cross-Sectional Studies; D005260:Female; D005843:Geography; D006262:Health; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood; D016014:Linear Models; D008297:Male; D009752:Nutritional Status / Q000502:physiology*; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000502:physiology*; D012015:Reference Standards; D012727:Sex Characteristics; D014481:United States; D014807:Vitamin D / Q000502:physiology*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000175:diagnosis
chemical_list: D015415:Biomarkers; D006887:Hydroxycholecalciferols; D010281:Parathyroid Hormone; D015675:Osteocalcin; D014807:Vitamin D; D002118:Calcium