Biochemical markers of bone turnover during pregnancy: a longitudinal study.
OBJECTIVE
The objective of this study was to prospectively investigate the effect of pregnancy on biochemical markers of bone turnover in healthy pregnant women.


METHODS
During the course of our longitudinal study, biochemical markers of bone remodeling were measured in all three trimester of pregnancy (first trimester: 12.5+/-1.8 SD, second trimester: 21.6+/-1 SD, third trimester: 34.8+/-1.6 SD weeks of gestation). Serum type I collagen C-telopeptides (CTX) and a crosslinked peptide of the carboxy-terminal telopeptide of type I collagen (ICTP) were used as markers of bone resorption. Bone alkaline phosphatase (BAP) and the N-terminal propeptides of type I collagen (PINP) were used as biochemical markers of bone formation. Blood samples for the analysis of all 4 biochemical markers according to each trimester of pregnancy were available in 49 patients.


RESULTS
The main changes for all biochemical markers were seen between the second and the third trimester. According to the markers of bone resorption, both serum CTX and ICTP showed a significant increase from the first to the third and from the second to the third trimester (p<0.001; median percentage change: CTX=101.5% and ICTP=40%). Concerning markers of bone formation, PINP showed a significant decrease from the first to the second trimester (p=0.001) followed by a significant increase from the second to the third trimester (p<0.001, 63.8%) and an overall increase from the first to the third trimester (p<0.001). BAP also showed a significant increase from the second to the third trimester (p<0.001; 51.7%) and an overall increase from the first to the third trimester (p<0.001).


CONCLUSIONS
Markers of bone resorption were significantly increased during pregnancy. In contrast to bone resorption, markers of bone formation showed an increase as well as a decrease during pregnancy indicating a state of high bone turnover. This might coincide with the change in bone mineral density that was observed in some, but not all, studies using "dual-energy x-ray absorptiometry" (DXA) as well as "quantitative ultrasonometry" (QUS).
Hellmeyer
L
L
Department of Obstetrics and Perinatal medicine, Philipps-University of Marburg. hellmeye@med.uni-marburg.de
Ziller
V
V
Anderer
G
G
Ossendorf
A
A
Schmidt
S
S
Hadji
P
P
D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers / Q000097:blood*; D016723:Bone Remodeling / Q000502:physiology*; D024042:Collagen Type I / Q000097:blood; D005260:Female; D005865:Gestational Age; D006801:Humans; D008137:Longitudinal Studies; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides / Q000097:blood; D011247:Pregnancy / Q000502:physiology*; D011347:Procollagen / Q000097:blood; D011446:Prospective Studies
D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C047202:procollagen Type I N-terminal peptide; D000469:Alkaline Phosphatase