University of Rochester School of Medicine, Rochester, NY, USA.
University of Pittsburgh School of Public Health, Pittsburgh, PA, USA.
Calcif Tissue Int. 2023 Oct;113(4):426-436. doi: 10.1007/s00223-023-01125-9. Epub 2023 Aug 28.
During lactation, changes in maternal calcium metabolism are necessary to provide adequate calcium for newborn skeletal development. The calcium in milk is derived from the maternal skeleton through a process thought to be mediated by the actions of parathyroid hormone-related protein (PTHrP) in combination with decreased circulating estrogen concentrations. After weaning, bone lost during lactation is rapidly regained. Most studies of bone metabolism in lactating women have been performed in Caucasian subjects. There are well-documented differences between African American (AA) and Caucasian (C) bone metabolism, including higher bone mineral density (BMD), lower risk of fracture, lower 25-hydroxyvitamin D (25(OH) D), and higher PTH in AA compared to C. In this prospective paired cohort study, BMD and markers of bone turnover were compared in self-identified AA and C mothers during lactation and after weaning. BMD decreased in both AA and C women during lactation, with similar decreases at the lumbar spine (LS) and greater bone loss in the C group at the femoral neck (FN) and total hip (TH), demonstrating that AA are not resistant to PTHrP during lactation. BMD recovery compared to the 2 week postpartum baseline was observed 6 months after weaning, though the C group did not have complete recovery at the FN. Increases in markers of bone formation and resorption during lactation were similar in AA and C. C-terminal telopeptide (CTX) decreased to 30% below post-pregnancy baseline in both groups 6 months after weaning, while procollagen type 1 N-terminal (P1NP) returned to baseline in the AA group and fell to below baseline in the C group. Further investigation is required to determine impacts on long term bone health for women who do not fully recover BMD before a subsequent pregnancy.
哺乳期母体钙代谢的变化对于为新生儿骨骼发育提供足够的钙是必要的。牛奶中的钙是通过一种被认为是由甲状旁腺激素相关蛋白（PTHrP）与循环雌激素浓度降低相结合的作用来从母体骨骼中获得的。断奶后，哺乳期丢失的骨迅速恢复。哺乳期妇女骨代谢的大多数研究都是在白种人受试者中进行的。非裔美国人（AA）和白种人（C）之间的骨骼代谢存在有据可查的差异，包括更高的骨密度（BMD）、骨折风险较低、25-羟维生素 D（25(OH) D）水平较低和 PTH 水平较高。在这项前瞻性配对队列研究中，比较了自我认同的 AA 和 C 母亲在哺乳期和断奶后的 BMD 和骨转换标志物。哺乳期 AA 和 C 女性的 BMD 均下降，腰椎（LS）下降相似，C 组股骨颈（FN）和总髋（TH）的骨丢失更大，表明 AA 在哺乳期不受 PTHrP 影响。与产后 2 周的基线相比，断奶后 6 个月观察到 BMD 恢复，但 C 组在 FN 处未完全恢复。哺乳期骨形成和吸收标志物的增加在 AA 和 C 中相似。断奶后 6 个月，CTX 下降到产后基线以下 30%，而 P1NP 在 AA 组恢复到基线，在 C 组降至基线以下。需要进一步研究，以确定对于那些在下一次怀孕前未完全恢复 BMD 的女性，对长期骨骼健康的影响。
