title: Associations of circulating calcium and 25-hydroxyvitamin D with glucose metabolism in pregnancy: a cross-sectional study in European and South Asian women.
abstract: BACKGROUND
  Vitamin D deficiency is thought to impair insulin action and glucose metabolism; however, previous studies have not examined ethnic differences or the influence of calcium and parathyroid hormone. We investigated this in a cohort of predominantly white European and south Asian women during pregnancy.
  
  
  METHODS
  In this cross-sectional study from an urban population in northern England (53.8°N), 1467 women were recruited when undergoing glucose tolerance testing (75 g oral glucose tolerance test) at 26 weeks' gestation.
  
  
  RESULTS
  Gestational diabetes mellitus (GDM) was diagnosed in 137 women (9.3%). Median 25-hydroxyvitamin D concentration for the study population was 9.3 ng/mL (interquartile range 5.2, 16.9) and was higher in European [15.2 ng/mL (10.7, 23.5)] than in south Asian women [5.9 ng/mL (3.9, 9.4), P < .001]. After appropriate adjustment for confounders, 25-hydroxyvitamin D showed a weak inverse association with fasting plasma glucose (FPG; mean difference 1.0% per 1 SD; the ratio of geometric means (RGM) 0.99, 95% confidence interval (CI) 0.98, 1.00), and PTH was weakly associated with FPG (RGM 1.01, 95% CI 1.00, 1.02), but neither was associated with fasting insulin, postchallenge glucose, or GDM. Serum calcium (albumin adjusted) was strongly associated with fasting insulin (RGM 1.06; 95% CI 1.03, 1.08), postchallenge glucose (RGM 1.03, 95% CI 1.01, 1.04), and GDM (odds ratio 1.33, 95% CI 1.06, 1.66) but not with FPG. Associations were similar in European and south Asian women.
  
  
  CONCLUSIONS
  These findings do not indicate any important association between vitamin D status and glucose tolerance in pregnancy. Relationships between circulating calcium and glucose metabolism warrant further investigation.
authors.affiliation: Departments of Diabetes and Endocrinology (D.C.W.), Obstetrics and Gynaecology (D.J.T.), and Pathology (T.J.D.) and Bradford Institute for Health Research (J.W.), Bradford Teaching Hospitals National Health Service Trust, Bradford BD9 6RJ, United Kingdom; School of Health Studies (A.J.S.), University of Bradford, Bradford BD7 1DP, United Kingdom; Department of Medicine (W.D.F.), Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, United Kingdom; Edinburgh Ethnicity and Health Research Group (R.S.B.), Centre for Population Health Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom; and Medical Research Council Centre for Causal Analyses in Translational Epidemiology (D.A.L.), School of Social and Community Medicine, University of Bristol, Bristol BS8 2BN, United Kingdom.
authors.forename: Donald C
authors.initials: DC
authors.lastname: Whitelaw
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Scally
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Tuffnell
authors.forename: T Jeffrey
authors.initials: TJ
authors.lastname: Davies
authors.forename: William D
authors.initials: WD
authors.lastname: Fraser
authors.forename: Raj S
authors.initials: RS
authors.lastname: Bhopal
authors.forename: John
authors.initials: J
authors.lastname: Wright
authors.forename: Debbie A
authors.initials: DA
authors.lastname: Lawlor
mesh_terms: D000328:Adult; D044466:Asian People / Q000706:statistics & numerical data; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism; D002118:Calcium / Q000097:blood*; D003430:Cross-Sectional Studies; D016640:Diabetes, Gestational / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology*; D004739:England / Q000453:epidemiology; D005260:Female; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D006801:Humans; D011247:Pregnancy / Q000378:metabolism*; D015995:Prevalence; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D005947:Glucose; D002118:Calcium