title: Vitamin D, parathyroid hormone, and blood pressure in the National Health and Nutrition Examination Surveys .
abstract: BACKGROUND
  Previous research shows serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) are each associated with blood pressure (BP), but it is unclear whether these associations are independent.
  
  
  METHODS
  Cross-sectional data from the US National Health and Nutrition Examination Surveys (NHANES) during 2003-2006. Analyses were restricted to 7,561 participants aged ≥20 years with measurements of 25(OH)D, PTH, BP, BP treatment, smoking, physical activity, serum calcium, and creatinine. Results were adjusted for these plus demographic variables.
  
  
  RESULTS
  Serum 25(OH)D was more strongly associated (inversely) with systolic than diastolic BP. Adjusted mean (standard error) difference in BP for the lowest 25(OH)D quintile (≤13 ng/ml) was 3.5 (0.7) mm Hg for systolic BP and 1.8 (0.6) mm Hg for diastolic BP, compared with the highest quintile (≥30 ng/ml). In contrast, PTH was positively associated with both systolic and diastolic BP (P < 0.0001). Adjusted mean (standard error) difference in BP for the highest PTH quintile (≥59 ng/l) was 5.9 (0.8) mm Hg for systolic BP and 4.5 (0.5) mm Hg for diastolic BP, compared with the lowest quintile (≤27 ng/l). When both 25(OH)D and PTH were included in the same model, the associations of PTH with systolic and diastolic BP were unchanged. However, the associations between 25(OH)D and BP were attenuated, with mean (standard error) difference between the highest and lowest quintiles being 2.2 (0.6) mm Hg for systolic BP (P < 0.01) and 0.8 (0.6) mm Hg for diastolic BP.
  
  
  CONCLUSIONS
  PTH may mediate most of the association between 25(OH)D and BP, which was not significant when also adjusting for body mass index.
authors.affiliation: School of Population Health, University of Auckland, Auckland, New Zealand.
authors.forename: Jack L
authors.initials: JL
authors.lastname: He
authors.forename: Robert K
authors.initials: RK
authors.lastname: Scragg
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D010281:Parathyroid Hormone / Q000097:blood*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D