title: Effects of age, sex, season and diet on serum ionized calcium, parathyroid hormone and vitamin D in a random population.
abstract: OBJECTIVE
  To study the influence of age, sex, season and diet on calcium status in normal subjects.
  
  
  METHODS
  A random population study. Setting. Institutional clinic for large population studies.
  
  
  METHODS
  The subjects were drawn randomly from the Danish Civil Registration System and represented a random sample of the background population in the area. The sample comprised 127 subjects (54 men and 73 women, aged 35-65 years).
  
  
  METHODS
  The effects of age, sex, season and diet on parathyroid hormone (PTH),1,25-dihydroxyvitamin D (1,25(OH)2D) and 25-hydroxyvitamin D (25-OHD).
  
  
  RESULTS
  There was no statistical significant difference for the serum concentrations of ionized calcium, PTH, 1,25(OH)2D and 25-OHD between the two sexes, nor any influence by age in either sex, in contrast to serum phosphate, which declined significantly in men (P < 0.05), but tended to increase in women. Serum PTH (P < 0.009) showed seasonal fluctuations, whereas serum concentrations of 1,25(OH)2D, 25-OHD, ionized calcium, phosphate and magnesium remained stable throughout the year. Dietary intake of calcium and vitamin D were not related to any serum variables.
  
  
  CONCLUSIONS
  In healthy subjects differences between the two sexes exist regarding phosphate metabolism. Serum PTH shows seasonal fluctuations.
authors.affiliation: Medical Department, Glostrup Hospital, University of Copenhagen, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Rudnicki
authors.forename: J
authors.initials: J
authors.lastname: Thode
authors.forename: T
authors.initials: T
authors.lastname: Jørgensen
authors.forename: B L
authors.initials: BL
authors.lastname: Heitmann
authors.forename: O H
authors.initials: OH
authors.lastname: Sørensen
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood; D002118:Calcium / Q000097:blood*; D003401:Creatine / Q000097:blood; D004032:Diet; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010710:Phosphates / Q000097:blood; D012621:Seasons; D012727:Sex Characteristics; D014807:Vitamin D / Q000097:blood*
chemical_list: D010281:Parathyroid Hormone; D010710:Phosphates; D014807:Vitamin D; D003401:Creatine; D002118:Calcium