title: Effect of perimenopause on calcium absorption: a longitudinal study.
abstract: OBJECTIVE
  Cross-sectional studies suggest that the rise in calcium requirement at the menopause may be attributable, at least in part, to a fall in intestinal calcium absorption. The aim of the present study was to determine the effect of the menopause on intestinal calcium absorption and the relationship between any change in calcium absorption and serum calcitriol.
  
  
  METHODS
  Radiocalcium absorption and serum calcitriol were measured in 72 women aged 47.3 (standard error, SE 0.19) years who were initially premenopausal (as judged by menstrual history and serum follicle stimulating hormone (FSH)) and again 18 months later.
  
  
  RESULTS
  Calcium absorption fell at the second visit from 0.72 (0.029)/h to 0.64 (0.029)/h (p = 0.003). Serum calcitriol had also fallen at the second visit from 124 (4.2) pmol/l to 111 (4.0) pmol/l (p = 0.007). At that visit, serum FSH exceeded the premenopausal reference range in 11 subjects and the menstrual cycle had become irregular in 24 of them. In the 11 women with raised FSH at the second visit, radiocalcium absorption fell from 0.85/h (0.097) at baseline to 0.57/h (0.049) (p = 0.008), but only from 0.70/h (0.028) to 0.65/h (0.033) (not significant) in the remaining 61. Similarly, radiocalcium absorption fell significantly (p = 0.003) in the 24 women with irregular menses, but not in the remaining 48 who continued to menstruate regularly. These changes in calcium absorption were still significant after correction for changes in calcitriol levels.
  
  
  CONCLUSIONS
  The perimenopause is associated with a fall in calcium absorption, which is only in part attributable to a fall in calcitriol levels.
authors.affiliation: Department of Medicine, University of Adelaide, Royal Adelaide Hospital, Adelaide, Australia.
authors.forename: J M
authors.initials: JM
authors.lastname: Wishart
authors.forename: F
authors.initials: F
authors.lastname: Scopacasa
authors.forename: M
authors.initials: M
authors.lastname: Horowitz
authors.forename: H A
authors.initials: HA
authors.lastname: Morris
authors.forename: A G
authors.initials: AG
authors.lastname: Need
authors.forename: P M
authors.initials: PM
authors.lastname: Clifton
authors.forename: B E
authors.initials: BE
authors.lastname: Nordin
mesh_terms: D000328:Adult; D002117:Calcitriol / Q000097:blood; D002118:Calcium / Q000493:pharmacokinetics*; D002132:Calcium Radioisotopes; D002136:Calcium, Dietary / Q000008:administration & dosage; D002979:Climacteric; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007408:Intestinal Absorption; D008875:Middle Aged; D009751:Nutritional Requirements
chemical_list: D002132:Calcium Radioisotopes; D002136:Calcium, Dietary; D004958:Estradiol; D005640:Follicle Stimulating Hormone; D002117:Calcitriol; D002118:Calcium