TAILIEUCHUNG - Chapter 047. Hypercalcemia and Hypocalcemia

The calcium ion plays a critical role in normal cellular function and signaling, regulating diverse physiologic processes such as neuromuscular signaling, cardiac contractility, hormone secretion, and blood coagulation. Thus, extracellular calcium concentrations are maintained within an exquisitely narrow range through a series of feedback mechanisms that involve parathyroid hormone (PTH) and the active vitamin D metabolite 1,25-dihydroxyvitmin D [1,25(OH)2D]. These feedback mechanisms are orchestrated by integrating signals between the parathyroid glands, kidney, intestine, and bone (Fig. 47-1) (Chap. 346). . | Chapter 047. Hypercalcemia and Hypocalcemia The calcium ion plays a critical role in normal cellular function and signaling regulating diverse physiologic processes such as neuromuscular signaling cardiac contractility hormone secretion and blood coagulation. Thus extracellular calcium concentrations are maintained within an exquisitely narrow range through a series of feedback mechanisms that involve parathyroid hormone PTH and the active vitamin D metabolite 1 25-dihydroxyvitmin D 1 25 OH 2D . These feedback mechanisms are orchestrated by integrating signals between the parathyroid glands kidney intestine and bone Fig. 47-1 Chap. 346 .Figure 47- I nlesline tỊạ-urcai F-iUfi A3. K ip r PL. jn ild Er 3L. Longo PL J m ori JL. Loỉ l o JI p fỉ djữĩ ĩ ữ mĩ . iTth Ldếtion. n. - ì .I .ji Feedback mechanisms maintaining extracellular calcium concentrations within a narrow physiologic range mg dL . A decrease in extracellular ECF calcium Ca2 triggers an increase in parathyroid hormone PTH secretion 1 via activation of the calcium sensor receptor on parathyroid cells. PTH in turn results in increased tubular reabsorption of calcium by the kidney 2 and resorption of calcium from bone 2 and also stimulates renal 1 25 OH 2D production 3 . 1 25 OH 2D in turn acts principally on the intestine to increase calcium absorption 4 . Collectively these homeostatic mechanisms serve to restore serum calcium levels to of serum calcium concentration are relatively common and often serve as a harbinger of underlying disease. This chapter provides a brief summary of the approach to patients with altered serum calcium levels. See Chap. 347 for a detailed discussion of this The causes of hypercalcemia can be understood and classified based on derangements in the normal feedback mechanisms that regulate serum calcium Table 47-1 . Excess PTH production which is not appropriately suppressed by

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