Hypercalcemia
Section snippets
Natural history of calcium
Although not discovered until 1808 by Davy, calcium is 1 of the most common of elements, comprising approximately 3% of the earth's crust. Calcium is found in all 3 major types of rocks (igneous, metamorphic, and sedimentary) and is present in high concentration (10 mmol/L) in seawater. Through the process of biomineralization, calcium salts form the basis for skeletal structure in organisms dating back to Precambrian times.1, 2 In addition to its structural roles, calcium also carries an
Maintenance of normal homeostasis
Ninety-nine percent of calcium is found in the skeleton, which serves as a vast reservoir or bank from which calcium can be drawn for homeostatic needs. Calcium homeostasis requires the maintenance of ionized serum calcium in the approximate range of 1 mmol/L or 4 mg/dL. Responsibility for the control of ionized serum calcium in mammalian species depends on the interaction among 3 calciotropic hormones (PTH, calcitonin, and vitamin D) and 3 target organs (kidney, bone, and intestine; Fig 7).
Primary hyperparathyroidism
Primary hyperparathyroidism is caused by inappropriate (for the ambient calcium concentration) PTH secretion by parathyroid adenoma(s), hyperplasia, or carcinoma. In hyperparathyroidism there are both increased cell proliferative activity (enlarged glands) and decreased sensitivity of the cells to secretory inhibition by calcium (altered set point). Sporadic primary hyperparathyroidism is the most common cause of hypercalcemia in an outpatient setting, with a prevalence of 1 per 500 women and 1
Hypercalcemic crisis
Most patients with hyperparathyroidism have relatively stable serum calcium levels. However, hypercalcemic crisis or severe hypercalcemia is a life-threatening emergency and, although more commonly encountered in patients with malignancy, can complicate primary hyperparathyroidism.200, 201 Although strict diagnostic criteria are lacking, hypercalcemic crisis can be defined as a serum calcium level of more than 14 mg/dL that is associated with acute signs and symptoms attributable to the
Indications for surgery
Patients with symptoms directly attributable to hyperparathyroidism should be offered surgical treatment. Patients with nephrolithiasis or nephrocalcinosis and those patients with overt bone disease are appropriate candidates for operation.218, 219
Currently, many patients with hyperparathyroidism, however, are identified as hypercalcemic by automated multiphasic serum chemistry screening. In these patients, the classic signs and symptoms of hyperparathyroidism may well be absent. In 1 series,
Postoperative hypocalcemia
In the immediate postoperative period, a decrease in serum calcium level is the expected result of a successful procedure. Patients who have extensive bone disease and/or have had subtotal or total parathyroidectomy and autotransplantation may become profoundly hypocalcemic, so it is useful to review the evaluation and treatment of acute hypocalcemia.234 Although calcium is required for a wide variety of physiologic processes, the effects of hypocalcemia on neuromuscular function are
Conclusion
Hypercalcemia is a common and potentially life-threatening condition. Understanding the basic mechanisms of calcium homeostasis and the abnormalities that occur in different diseases is critical to safe, successful, and cost-effective patient treatment. Current research has begun to define many of the molecular mutations that underlie the common causes of hypercalcemia. However, definitive treatment of the most common cause of hypercalcemia, hyperparathyroidism, remains surgical resection. With
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