Kovacs Christopher S
Faculty of Medicine, Memorial University of Newfoundland, Health Sciences Centre, 300 Prince Philip Drive, St. John's, NL, A1B 3V6, Canada,
Pediatr Nephrol. 2014 May;29(5):793-803. doi: 10.1007/s00467-013-2461-4. Epub 2013 Mar 26.
During embryonic development most of the skeleton begins as a cartilaginous scaffold that is progressively resorbed and replaced by bone. Such endochondral bone development does not cease until the growth plates fuse during puberty. Growth and mineralization of the skeleton are dependent upon the adequate delivery of mineral. During fetal development, the placenta actively transports calcium, magnesium and phosphorus from the maternal circulation. After birth, the role of mineral transport is assumed by the intestines. The limited data currently available on fetal humans are largely based on cord blood samples from normal fetuses and pathological specimens from fetuses which died in utero or at birth. Consequently, much of our understanding of the regulation of fetal mineral and bone homeostasis comes from the study of animal fetuses that have been manipulated surgically, pharmacologically and genetically. Animal and human data indicate that fetal mineral homeostasis requires parathyroid hormone (PTH) and PTH-related protein-but not vitamin D/calcitriol, calcitonin or sex steroids. In the days to weeks after birth, intestinal calcium absorption becomes an active process, which necessitates that the infant depends upon vitamin D/calcitriol. However, even this postnatal function of calcitriol can be bypassed by increasing the calcium content of the diet or by administering calcium infusions.
在胚胎发育过程中，大部分骨骼最初是一个软骨支架，随后逐渐被吸收并被骨骼替代。这种软骨内成骨发育直到青春期生长板融合才停止。骨骼的生长和矿化依赖于矿物质的充足供应。在胎儿发育期间，胎盘积极地从母体循环中转运钙、镁和磷。出生后，矿物质转运的功能由肠道承担。目前关于人类胎儿的有限数据主要基于正常胎儿的脐带血样本以及死于子宫内或出生时的胎儿的病理标本。因此，我们对胎儿矿物质和骨稳态调节的许多理解来自对经过手术、药理学和遗传学操作的动物胎儿的研究。动物和人类数据表明，胎儿矿物质稳态需要甲状旁腺激素（PTH）和甲状旁腺激素相关蛋白，但不需要维生素D/骨化三醇、降钙素或性类固醇。在出生后的几天到几周内，肠道钙吸收成为一个活跃的过程，这使得婴儿依赖维生素D/骨化三醇。然而，即使是骨化三醇的这种产后功能也可以通过增加饮食中的钙含量或给予钙输注来绕过。
