Departments of Medicine and of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, New York, USA.
Clin J Am Soc Nephrol. 2010 Jan;5 Suppl 1:S12-22. doi: 10.2215/CJN.05970809.
Calcium (Ca) balance is the net of Ca intake and output from the body over a period of time. The concept of Ca balance does not consider the redistribution of Ca that often occurs in patients with chronic kidney disease (CKD), especially those who are on dialysis, which is often in the form of soft tissue and/or vascular calcification. In this article, we consider movement of Ca with respect to the extracellular fluid (ECF) and develop a mathematical formulation for Ca homeostasis with respect to the ECF that includes input and output from the diet, the bone, the kidney, and dialysis. We consider calcium homeostasis in healthy individuals and in patients with excess parathyroid hormone, excess 1,25-dihydroxyvitamin D(3), and metabolic acidosis; patients who have CKD and are not on dialysis; and, finally, patients who have CKD and are on dialysis. On the basis of a number of assumptions, dialysis patients with a daily intake of >37.5 mmol of elemental Ca (1.5 g) have movement of Ca into the ECF even without supplemental activated vitamin D. Addition of activated vitamin D, which increases intestinal Ca absorption and can increase resorption of Ca from bone, leads to the movement of Ca into the ECF at virtually all levels of intake; however, there are numerous unanswered questions regarding Ca homeostasis in patients with CKD, including how much of the Ca, administered as a phosphate binder, is absorbed and what is the fate of this absorbed Ca. Until these pressing questions are answered with well-designed experiments, we do not know whether we are doing more harm than good for our dialysis patients by administering additional Ca as a phosphate binder, especially when they also receive activated vitamin D.
钙（Ca）平衡是指一段时间内身体摄入和排出 Ca 的净量。Ca 平衡的概念没有考虑到慢性肾脏病（CKD）患者中经常发生的 Ca 再分布，尤其是那些正在接受透析治疗的患者，这种再分布通常表现为软组织和/或血管钙化。在本文中，我们考虑 Ca 在外液（ECF）中的移动，并针对 ECF 建立了一个 Ca 动态平衡的数学公式，该公式包括饮食、骨骼、肾脏和透析的输入和输出。我们考虑了健康个体以及甲状旁腺激素过多、1,25-二羟维生素 D（3）过多和代谢性酸中毒患者、未接受透析治疗的 CKD 患者以及接受透析治疗的 CKD 患者的钙动态平衡。基于一些假设，每天摄入>37.5mmol 元素 Ca（1.5g）的透析患者，即使没有补充活性维生素 D，也会有 Ca 进入 ECF。添加活性维生素 D 可增加肠道 Ca 吸收，并增加骨中 Ca 的重吸收，导致在几乎所有摄入水平下 Ca 都进入 ECF；然而，关于 CKD 患者的钙动态平衡仍有许多未解决的问题，包括作为磷酸盐结合剂给予的 Ca 中有多少被吸收，以及被吸收的 Ca 的命运如何。在这些紧迫的问题通过精心设计的实验得到解答之前，我们并不知道通过给予额外的 Ca 作为磷酸盐结合剂来治疗我们的透析患者是否弊大于利，尤其是当他们还接受活性维生素 D 治疗时。
