title: Interrelationship between bone turnover markers and dietary calcium intake in pregnant women: a longitudinal study.
abstract: This longitudinal study evaluated bone turnover and the interrelationship between changes in bone biomarkers and habitual dietary calcium intake during pregnancy in a group of women ranging widely with regard to dietary calcium intake. Thirty-nine healthy pregnant and 30 nonpregnant women were studied. Calcium, phosphorus, 1alpha,25-dihydroxyvitamin D (1,25diHOD), bone alkaline phosphatase (bALP), carboxyterminal propeptides of type I procollagen (PICP) and carboxyterminal telopeptides of type I collagen (betaCTX and ICTP) were measured in serum and calcium, and creatinine and aminoterminal telopeptide (NTX) were determined in urine. Serum calcium and phosphorus did not change but the urinary Ca/Creat ratio and 1,25diHOD increased throughout pregnancy (P < 0.001 and P < 0.0001, respectively). Serum b-ALP and PICP increased during the last two trimesters (P < 0.0001 and P < 0.001, respectively). All studied bone resorption markers increased compared to nonpregnant values throughout pregnancy. The highest increment was observed in the third trimester. The level of significance decreased as follows: betaCTX > NTX >ICTP. Serum 1,25 diHOD versus calcium intake showed a positive and significant correlation (r = 0.51, P < 0.02). A negative correlation between the absolute change in betaCTX, NTX, and b-ALP between the third and second trimester and calcium intake at the end of pregnancy was observed in pregnant women who did not cover adequately calcium intake requirements (r = -0.47, P < 0.03; r = -0.41, P < 0.05; and r = -0.43, P < 0.05, respectively). These results suggest that skeletal response to pregnancy may not be entirely independent of maternal calcium intake, especially in women with usually low calcium intake. In summary, not only hormonal changes in calcium metabolism that occur during pregnancy but also other considerations, such as low dietary calcium intake, may lead to an increment in the biological activity of the skeleton. Additional studies must be conducted to confirm our findings and to gain a better understanding of skeletal response to a low calcium intake during pregnancy.
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Sección Osteopatías Médicas del Hospital de Clínicas J. de San Martin, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina. osteologia@ciudad.com.ar
authors.forename: Susana N
authors.initials: SN
authors.lastname: Zeni
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Ortela Soler
authors.forename: Araceli
authors.initials: A
authors.lastname: Lazzari
authors.forename: Laura
authors.initials: L
authors.lastname: López
authors.forename: Marisa
authors.initials: M
authors.lastname: Suarez
authors.forename: Silvana
authors.initials: S
authors.lastname: Di Gregorio
authors.forename: Julia I
authors.initials: JI
authors.lastname: Somoza
authors.forename: Maria L
authors.initials: ML
authors.lastname: de Portela
mesh_terms: D000293:Adolescent; D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers / Q000032:analysis; D016723:Bone Remodeling / Q000187:drug effects* / Q000502:physiology*; D002117:Calcitriol / Q000097:blood; D002118:Calcium / Q000097:blood / Q000652:urine; D002136:Calcium, Dietary / Q000008:administration & dosage*; D016022:Case-Control Studies; D003094:Collagen / Q000097:blood; D024042:Collagen Type I; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides / Q000097:blood; D010758:Phosphorus / Q000097:blood; D011247:Pregnancy / Q000378:metabolism*; D011347:Procollagen / Q000097:blood
chemical_list: D015415:Biomarkers; D002136:Calcium, Dietary; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C042813:procollagen type I carboxy terminal peptide; D010758:Phosphorus; D003094:Collagen; D003404:Creatinine; D000469:Alkaline Phosphatase; D002117:Calcitriol; D002118:Calcium