Metabolic turnover of bone during pregnancy and puerperium

It has been considered that bone mass is usually maintained during pregnancy by high level of estrogens but drastic decrease of estrogens lead to bone loss during lactation. Metabolic turnover of bone during pregnancy and in puerperium was studied by analyzing biomarkers of bone turnover and cytokine released by peripheral blood mononuclear cells. Urinary excretion of pyridinoline (Pyr) and deoxypyridinoline (D-Pyr), and serum tartrate resistant acid phosphatase (TrACP), which are biomarkers of bone resorption, were increased in the last trimester of pregnancy. Plasma level of intact osteocalcin (I-OC), which is a biomarker of bone formation, decreased in the 2nd trimester and slightly increased in the 3rd. Tumor necrosis factor (TNF)- alpha, which is one of cytokines to stimulate bio-activity of osteoclast, increased during pregnancy. According to these results, we conclude that decrease in bone mass begins already during pregnancy despite of a high estrogen state.