title: Evaluation of markers of bone turnover during lactation in African-Americans: a comparison with Caucasian lactation.
abstract: BACKGROUND
  The African-American skeleton is resistant to PTH; whether it is also resistant to PTHrP and the hormonal milieu of lactation is unknown.
  
  
  OBJECTIVE
  The objective of the study was to assess bone turnover markers in African-Americans during lactation vs Caucasians.
  
  
  METHODS
  A prospective cohort study with repeated measures of markers of bone turnover in 60 African-American women (3 groups of 20: lactating, bottle feeding, and healthy controls), compared with historic Caucasian women.
  
  
  METHODS
  The study was conducted at a university medical center.
  
  
  METHODS
  Biochemical markers of bone turnover and calcium metabolism were measured.
  
  
  RESULTS
  25-Hydroxyvitamin D (25-OHD) and PTH were similar among all 3 African-American groups, but 25-OHD was 30%-50% lower and PTH 2-fold higher compared with Caucasians (P < .001, P < .002), with similar 1,25 dihydroxyvitamin D [1,25(OH)(2)D] values. Formation markers [amino-terminal telopeptide of procollagen-1 (P1NP) and bone-specific alkaline phosphatase (BSAP)] increased significantly (2- to 3-fold) in lactating and bottle-feeding African-American women (P1NP, P < .001; BSAP, P < .001), as did resorption [carboxy-terminal telopeptide of collagen-1 (CTX) and serum amino-terminal telopeptide of collagen 1 (NTX), both P < .001]. P1NP and BSAP were comparable in African-American and Caucasian controls, but CTX and NTX were lower in African-American vs Caucasian controls. African-American lactating mothers displayed quantitatively similar increases in markers of bone formation but slightly lower increases in markers of resorption vs Caucasians (P = .036).
  
  
  CONCLUSIONS
  Despite reported resistance to PTH, lactating African-American women have a significant increase in markers of bone resorption and formation in response the hormonal milieu of lactation. This response is similar to that reported in Caucasian women despite racial differences in 25-OHD and PTH. Whether this is associated with similar bone loss in African-Americans as in Caucasians during lactation is unknown and requires further study.
authors.affiliation: University of Fortaleza School of Medicine, Fortaleza, Ceará , Brazil.
authors.forename: Raquel M
authors.initials: RM
authors.lastname: Carneiro
authors.forename: Linda
authors.initials: L
authors.lastname: Prebehalla
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Tedesco
authors.forename: Susan M
authors.initials: SM
authors.lastname: Sereika
authors.forename: Caren M
authors.initials: CM
authors.lastname: Gundberg
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Stewart
authors.forename: Mara J
authors.initials: MJ
authors.lastname: Horwitz
mesh_terms: D000328:Adult; D001741:Black or African American; D015415:Biomarkers / Q000097:blood; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003094:Collagen / Q000097:blood; D005260:Female; D006801:Humans; D007774:Lactation / Q000097:blood*; D010012:Osteogenesis / Q000502:physiology*; D010281:Parathyroid Hormone / Q000097:blood; D011446:Prospective Studies; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D044465:White People
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D003094:Collagen; C104450:25-hydroxyvitamin D; D002118:Calcium