title: Pakistanis living in Oslo have lower serum 1,25-dihydroxyvitamin D levels but higher serum ionized calcium levels compared with ethnic Norwegians. The Oslo Health Study.
abstract: BACKGROUND
  Persons of Pakistani origin living in Oslo have a much higher prevalence of vitamin D deficiency and secondary hyperparathyroidism but similar bone mineral density compared with ethnic Norwegians. Our objective was to investigate whether Pakistani immigrants living in Oslo have an altered vitamin D metabolism by means of compensatory higher serum levels of 1,25-dihydroxyvitamin D (s-1,25(OH)2D) compared with ethnic Norwegians; and whether serum levels of ionized calcium (s-Ca2+) differ between Pakistanis and Norwegians.
  
  
  METHODS
  In a cross-sectional, population-based study venous serum samples were drawn from 94 Pakistani men and 67 Pakistani women aged 30-60 years, and 290 Norwegian men and 270 Norwegian women aged 45-60 years; in total 721 subjects.
  
  
  RESULTS
  Pakistanis had lower s-1,25(OH)2D compared with Norwegians (p < 0.001). Age- and gender adjusted mean (95% CI) levels were 93 (86, 99) pmol/l in Pakistanis and 123 (120, 126) pmol/l in Norwegians, p < 0.001. The difference persisted after controlling for body mass index. There was a positive relation between serum 25-hydroxyvitamin D (s-25(OH)D) and s-1,25(OH)2D in both groups. S-Ca2+ was higher in Pakistanis; age-adjusted mean (95% CI) levels were 1.28 (1.27, 1.28) mmol/l in Pakistanis and 1.26 (1.26, 1.26) mmol/l in Norwegians, p < 0.001. In both groups, s-Ca2+ was inversely correlated to serum intact parathyroid hormone levels (s-iPTH). For any s-iPTH, s-Ca2+ was higher in Pakistanis, also when controlling for age.
  
  
  CONCLUSIONS
  Community-dwelling Pakistanis in Oslo with low vitamin D status and secondary hyperparathyroidism have lower s-1,25(OH)2D compared with ethnic Norwegians. However, the Pakistanis have higher s-Ca2+. The cause of the higher s-Ca2+ in Pakistanis in spite of their higher iPTH remains unclear.
authors.affiliation: Institute of General Practice and Community Medicine, University of Oslo, PO Box 1130 Blindern, NO-0318 Oslo, Norway. kristin.holvik@medisin.uio.no
authors.forename: Kristin
authors.initials: K
authors.lastname: Holvik
authors.forename: Haakon E
authors.initials: HE
authors.lastname: Meyer
authors.forename: Anne Johanne
authors.initials: AJ
authors.lastname: Søgaard
authors.forename: Egil
authors.initials: E
authors.lastname: Haug
authors.forename: Jan A
authors.initials: JA
authors.lastname: Falch