Bone turnover from early pregnancy to postweaning.
BACKGROUND
To elucidate the sequences of changes in bone metabolism and bone density during pregnancy, lactation and postweaning.


METHODS
Women were recruited (n = 254) in early pregnancy and followed for 2 years. Markers of bone formation (osteocalcin) and resorption (NTx) were measured at five occasions. Bone mineral density (BMD) of whole-body and lumbar spine L1-L4 (DXA) and ultrasonography of os calcis were measured in a subgroup (n = 14).


RESULTS
NTx appeared bone specific in comparison to pyridinolines. NTx started to increase early in pregnancy and remained elevated during lactation (p < 0.001). Osteocalcin was low during pregnancy, but peaked during lactation (p < 0.018). The subsequent decrease was associated with time since resumption of menses (r2 = 0.23; p < 0.001). There was indication of a decrease in calcaneal bone mass during pregnancy and an evident decrease in lumbar spine (p = 0.041) and os calcis (p = 0.037) during lactation. No detectable decrease was identified in whole-body BMD (p = 0.090) during lactation, but in general, BMD was higher in whole-body (1.9%) and lumbar spine (6.6%) 18 months postpartum than during puerperium (p = 0.003).


CONCLUSIONS
According to the bone metabolic markers, bone resorption increased early in pregnancy and remained elevated over lactation, while bone formation increased during lactation, probably regulated by mechanisms associated with absence of menses. The high metabolic bone turnover during late pregnancy and lactation lead to a decline in cancellous bone mass during lactation, but this seemed beneficial for BMD postweaning.
Institute of Environmental Medicine, Division of Metals and Health, Karolinska Institutet, Stockholm, Sweden. Agneta.Akesson@imm.ki.se
Agneta
A
Akesson
Marie
M
Vahter
Marika
M
Berglund
Tuula
T
Eklöf
Katarina
K
Bremme
Per
P
Bjellerup
D015502:Absorptiometry, Photon; D000328:Adult; D015519:Bone Density; D001862:Bone Resorption; D005260:Female; D006801:Humans; D007774:Lactation / Q000502:physiology*; D008137:Longitudinal Studies; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D011247:Pregnancy / Q000502:physiology*; D014886:Weaning
D015675:Osteocalcin