Bone calcium turnover during pregnancy and lactation in women with low calcium diets is associated with calcium intake and circulating insulin-like growth factor 1 concentrations

BACKGROUND: Few data exist on longitudinal changes in bone calcium turnover rates across pregnancy and lactation. OBJECTIVE: Our aim was to characterize calcium kinetic variables and predictors of these changes across pregnancy and early lactation in women with low calcium intakes. DESIGN: Stable calcium isotopes were administered to 10 Brazilian women during early pregnancy (EP; weeks 10-12 of gestation), late pregnancy (LP; weeks 34-36 of gestation), and early lactation (EL; 7-8 wk postpartum). Multicompartmental modeling was used to assess the rates of bone calcium turnover in relation to calcium intakes and circulating concentrations of parathyroid hormone (PTH), insulin-like growth factor 1, and 1,25-dihydroxyvitamin D. RESULTS: Rates of bone calcium deposition increased significantly from EP to LP (P = 0.001) and were significantly associated with serum PTH during LP (P