title: Relationships between lead biomarkers and diurnal salivary cortisol indices in pregnant women from Mexico City: a cross-sectional study.
abstract: BACKGROUND
  Lead (Pb) exposure during pregnancy may increase the risk of adverse maternal, infant, or childhood health outcomes by interfering with hypothalamic-pituitary-adrenal-axis function. We examined relationships between maternal blood or bone Pb concentrations and features of diurnal cortisol profiles in 936 pregnant women from Mexico City.
  
  
  METHODS
  From 2007-11 we recruited women from hospitals/clinics affiliated with the Mexican Social Security System. Pb was measured in blood (BPb) during the second trimester and in mothers' tibia and patella 1-month postpartum. We characterized maternal HPA-axis function using 10 timed salivary cortisol measurements collected over 2-days (mean: 19.7, range: 14-35 weeks gestation). We used linear mixed models to examine the relationship between Pb biomarkers and cortisol area under the curve (AUC), awakening response (CAR), and diurnal slope.
  
  
  RESULTS
  After adjustment for confounders, women in the highest quintile of BPb concentrations had a reduced CAR (Ratio: -13%; Confidence Interval [CI]: -24, 1, p-value for trend < 0.05) compared to women in the lowest quintile. Tibia/patella Pb concentrations were not associated with CAR, but diurnal cortisol slopes were suggestively flatter among women in the highest patella Pb quantile compared to women in the lowest quantile (Ratio: 14%; CI: -2, 33). BPb and bone Pb concentrations were not associated with cortisol AUC.
  
  
  CONCLUSIONS
  Concurrent blood Pb levels were associated with cortisol awakening response in these pregnant women and this might explain adverse health outcomes associated with Pb. Further research is needed to confirm these results and determine if other environmental chemicals disrupt hypothalamic-pituitary-adrenal-axis function during pregnancy.
authors.affiliation: Department of Epidemiology, Brown University, 121 S, Main St, Providence, RI 02912, USA. joseph_braun_1@brown.edu.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Braun
authors.forename: Rosalind J
authors.initials: RJ
authors.lastname: Wright
authors.forename: Allan C
authors.initials: AC
authors.lastname: Just
authors.forename: Melinda C
authors.initials: MC
authors.lastname: Power
authors.forename: Marcela
authors.initials: M
authors.lastname: Tamayo Y Ortiz
authors.forename: Lourdes
authors.initials: L
authors.lastname: Schnaas
authors.forename: Howard
authors.initials: H
authors.lastname: Hu
authors.forename: Robert O
authors.initials: RO
authors.lastname: Wright
authors.forename: Martha Maria
authors.initials: MM
authors.lastname: Tellez-Rojo
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000032:analysis; D002940:Circadian Rhythm; D002947:Cities; D003430:Cross-Sectional Studies; D004785:Environmental Pollutants / Q000032:analysis*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D007854:Lead / Q000032:analysis*; D008800:Mexico; D010329:Patella / Q000737:chemistry*; D011247:Pregnancy / Q000502:physiology; D012463:Saliva / Q000737:chemistry*; D013977:Tibia / Q000737:chemistry*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D004785:Environmental Pollutants; D007854:Lead; D006854:Hydrocortisone