title: Vitamin D and parathyroid hormone status in pregnancy: effect on insulin sensitivity, β-cell function, and gestational diabetes mellitus.
abstract: BACKGROUND
  Previous studies have yielded conflicting findings on the relationship between vitamin D deficiency/insufficiency and gestational diabetes mellitus (GDM). We hypothesized that PTH may be an underlying factor relevant to this potential association.
  
  
  OBJECTIVE
  This study sought to evaluate the effect of vitamin D and PTH status on insulin sensitivity, β-cell function, and glycemia in pregnancy.
  
  
  METHODS
  Five-hundred-twenty-four women underwent a glucose challenge test (GCT) and oral glucose tolerance test (OGTT) in late second/early third trimester. The GCT/OGTT identified 142 women with GDM, 94 with gestational impaired glucose tolerance, 163 with an abnormal GCT and normal OGTT, and 125 with normal GCT and OGTT.
  
  
  RESULTS
  Glycemia was assessed by glucose tolerance status and area under the glucose curve (AUC(gluc)) on the OGTT. Insulin sensitivity and β-cell function were assessed by Matsuda index and Insulin Secretion-Sensitivity Index-2 (ISSI-2), respectively.
  
  
  RESULTS
  There were 166 women (31.7%) with vitamin D deficiency (25-OH-D < 50 nmol/L), 178 (34%) with insufficiency (25-OH-D ≥ 50 nmol/L and < 75 nmol/L), and 180 (34.3%) with sufficiency (25-OH-D ≥ 75 nmol/L). Vitamin D status was not associated with Matsuda index, ISSI-2, AUC(gluc), or glucose tolerance status. In contrast, ISSI-2 decreased and AUC(gluc) increased across ascending tertiles of PTH (P = .06 and P = .002, respectively). Indeed, the prevalence of GDM progressively increased from the first (22.6%) to second (25.8%) to third (33.5%) tertile of PTH (P < .001). On logistic regression analyses, the third tertile of PTH was independently associated with GDM (adjusted OR = 1.82; 95% CI, 1.09-3.02; P = .022), whereas vitamin D deficiency and insufficiency were not significant predictors of GDM.
  
  
  CONCLUSIONS
  Increased PTH, rather than vitamin D deficiency/insufficiency, is independently associated with dysglycemia in pregnancy.
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., B.S., A.J.H., B.Z., R.R.), Mt Sinai Hospital, Toronto, Canada M5T 3L9; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), Department of Medicine, University of Toronto, Toronto, Canada M5S 1A1; Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, Canada M5S 1A1; Keenan Research Centre for Biomedical Science of St. Michael's Hospital (P.W.C.), Toronto, Canada M5B 1W8; Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, Canada M5T 3L9; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mt Sinai Hospital, Toronto, Canada M5T 3L9.
authors.forename: Caroline K
authors.initials: CK
authors.lastname: Kramer
authors.forename: Balakumar
authors.initials: B
authors.lastname: Swaminathan
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Hanley
authors.forename: Philip W
authors.initials: PW
authors.lastname: Connelly
authors.forename: Mathew
authors.initials: M
authors.lastname: Sermer
authors.forename: Bernard
authors.initials: B
authors.lastname: Zinman
authors.forename: Ravi
authors.initials: R
authors.lastname: Retnakaran
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015331:Cohort Studies; D016640:Diabetes, Gestational / Q000097:blood*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D009752:Nutritional Status; D010281:Parathyroid Hormone / Q000097:blood*; D011247:Pregnancy; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications
chemical_list: D001786:Blood Glucose; D010281:Parathyroid Hormone; D014807:Vitamin D