title: Contribution of calcium, phosphorus and 25-hydroxyvitamin D to the excessive severity of secondary hyperparathyroidism in African-Americans with CKD.
abstract: BACKGROUND
  Parathyroid hormone (PTH) levels in African-American (AA) chronic kidney disease (CKD) patients exceed those in patients of other races; mechanisms are unknown.
  
  
  METHODS
  We performed a cross-sectional analysis of initial laboratory data collected on 2028 CKD patients (505 AA) from US practices using a laboratory CKD service. Serum calcium (Ca), phosphorus (P), 25-hydroxyvitamin D (25-D) and plasma PTH levels were compared between the two groups.
  
  
  RESULTS
  Mean PTH for AA exceeded PTH for non-AA in Stages 2-5 (P<0.001, all four stages). 25-D levels were higher for non-AA in Stages 1-3 (P<0.001). Serum Ca and P did not differ between groups at any stage. Full adjustment for these variables using multivariable generalized linear modeling did not remove the effect of AA race: AA PTH values exceeded non-AA values in CKD Stages 2-5 (P<0.02, all four stages). Serum Ca, P and 25-D were all inversely correlated with PTH levels irrespective of race, but all factors combined accounted for ∼42% of the variance in PTH.
  
  
  CONCLUSIONS
  PTH rises with progressive CKD stage far more in AA than in non-AA patients, and only a moderate component of the rise in PTH is explained by changes in serum Ca, P and 25-D in either group. These findings concur with those from other large CKD cohorts and support the need for further study to determine other factors responsible for this racial difference.
authors.affiliation: Litholink Corporation, Chicago, IL, USA. ennisj1@labcorp.com
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ennis
authors.forename: Elaine
authors.initials: E
authors.lastname: Worcester
authors.forename: Fredric
authors.initials: F
authors.lastname: Coe
mesh_terms: D001741:Black or African American / Q000706:statistics & numerical data*; D000368:Aged; D002118:Calcium / Q000378:metabolism*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005006:Ethnicity / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000208:ethnology* / Q000209:etiology / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010758:Phosphorus / Q000378:metabolism*; D011379:Prognosis; D051436:Renal Insufficiency, Chronic / Q000150:complications / Q000208:ethnology* / Q000378:metabolism; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D014807:Vitamin D; D010758:Phosphorus; C104450:25-hydroxyvitamin D; D002118:Calcium