title: The relationship between PTH and 25-hydroxy vitamin D early in pregnancy.
abstract: OBJECTIVE
  Measure serum PTH and 25(OH)D in a cross-sectional sample of pregnant women at 11th through 13th weeks' gestation to examine vitamin D status and consider implications.
  
  
  METHODS
  Observational: we retrieved residual sera stored at -20 °C after routine first trimester Down's syndrome screening, distributed over 12 months.
  
  
  METHODS
  430 African American women and 586 Caucasian women.
  
  
  METHODS
  PTH and 25-hydroxy vitamin D [25(OH)D] immunoassays.
  
  
  RESULTS
  PTH medians were: 1·33 pmol/l (African American women); 1·20 pmol/l (Caucasian women) (t = 0·43, P = 0·7). Concentrations were highest in winter and decreased significantly in spring, fall, and summer. There was a direct PTH/weight relationship in Caucasian (t = 3·12, P < 0·002), but not African American women (t = 1·34, P = 0·18). Median 25(OH)D concentrations were 47·5 nmol/l (African American women) and 65 nmol/l (Caucasian women) (t = 13·7, P < 0·001). Concentrations were lowest in winter and rose significantly in spring, fall, and summer. Reciprocal 25(OH)D/weight relationships existed for both racial groups (t =-4·31 P < 0·001; t = 4·54, P < 0·001, respectively). Among 68 Caucasian women who smoked, median PTH and 25(OH)D concentrations were somewhat lower (P = ns). In separate regression models with PTH and 25(OH)D [dependent variables] and season, weight and smoking [independent variables], the only qualifying interactive term was in the Caucasian PTH model (season*1/weight). A regression model applied to adjusted scatter plots of PTH vs 25(OH)D indicated a weak relationship.
  
  
  CONCLUSIONS
  The PTH/25(OH)D relationship is weaker during early pregnancy than in non-pregnant adults, making it unreliable for estimating vitamin D sufficiency. A suitable reference point for sufficiency might be the maternal 25(OH)D level considered sufficient for adequate transfer to neonates.
authors.affiliation: Division of Medical Screening and Special Testing, Department of Pathology and Laboratory Medicine, Women & Infants Hospital/Alpert Medical School of Brown University, Providence, RI, USA. jhaddow@ipmms.org
authors.forename: James E
authors.initials: JE
authors.lastname: Haddow
authors.forename: Louis M
authors.initials: LM
authors.lastname: Neveux
authors.forename: Glenn E
authors.initials: GE
authors.lastname: Palomaki
authors.forename: Geralyn
authors.initials: G
authors.lastname: Lambert-Messerlian
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Canick
authors.forename: David G
authors.initials: DG
authors.lastname: Grenache
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
mesh_terms: D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D001835:Body Weight; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D010281:Parathyroid Hormone / Q000097:blood*; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood* / Q000208:ethnology; D012044:Regression Analysis; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D044465:White People / Q000706:statistics & numerical data
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D