title: Size at birth, adult intestinal calcium absorption and 1,25(OH)(2) vitamin D.
abstract: BACKGROUND
  Adult bone mineral status is modified by early environmental influences, but the mechanism of this phenomenon is unknown. Intestinal calcium absorption and vitamin D metabolism are integrally involved in bone metabolism and may be programmed during early life.
  
  
  OBJECTIVE
  To examine the early-life influences on calcium absorption and its control in 322 post-menopausal female twins.
  
  
  METHODS
  Intestinal calcium absorption was assessed by the stable strontium (Sr) method. Serum PTH, 25(OH) and 1,25(OH)(2) vitamin D were measured and recalled birth weight recorded.
  
  
  RESULTS
  Fractional intestinal Sr absorption (alpha Sr) was correlated with serum 1,25(OH)(2) vitamin D (p<0.001), but not with 25(OH) vitamin D. Birth weight was inversely associated with serum 1,25(OH)(2) vitamin D (p=0.04), the association being independent of serum calcium, phosphate, creatinine and PTH. Birth weight was inversely correlated with alpha Sr (p=0.03), this association being independent of age, season, customary calcium intake and serum 25(OH) vitamin D; however, when serum 1,25(OH)(2) vitamin D was added into the model, the association became non-significant, suggesting that the association was partially mediated via serum 1,25(OH)(2) vitamin D.
  
  
  CONCLUSIONS
  We found a significant inverse association between birth weight and intestinal calcium absorption that is partially explained by an association between serum 1,25(OH)(2) vitamin D and birth weight. This suggests a mechanism whereby the intra-uterine environment might affect adult skeletal status.
authors.affiliation: MRC Environmental Epidemiology Unit, Southampton General Hospital, Southampton, UK. nka@mrc.soton.ac.uk
authors.forename: N K
authors.initials: NK
authors.lastname: Arden
authors.forename: P
authors.initials: P
authors.lastname: Major
authors.forename: J R
authors.initials: JR
authors.lastname: Poole
authors.forename: R W
authors.initials: RW
authors.lastname: Keen
authors.forename: S
authors.initials: S
authors.lastname: Vaja
authors.forename: R
authors.initials: R
authors.lastname: Swaminathan
authors.forename: C
authors.initials: C
authors.lastname: Cooper
authors.forename: T D
authors.initials: TD
authors.lastname: Spector
mesh_terms: D000368:Aged; D001724:Birth Weight / Q000502:physiology*; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007408:Intestinal Absorption / Q000502:physiology*; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012042:Registries; D012044:Regression Analysis; D013324:Strontium; D014427:Twins; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood*
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D002118:Calcium; D013324:Strontium