A Practical Approach to Hypercalcemia - American Family Physician

www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 1959 other inorganic molecules. Low albumin levels can affect the total serum calcium level. Directly measuring the free calcium level is more convenient and accurate, but the following formula can be used to calculate the corrected total serum calcium level: Corrected calcium = (4.0 g per dL − [plasma albumin]) 0.8 + [serum calcium] Parathyroid hormone (PTH), 1,25-dihydroxyvitamin D3 (calcitriol), and calcitonin control calcium homeostasis in the body (Table 1). Increased bone resorption, increased gastrointestinal absorption of calcium, and decreased renal excretion of calcium cause hypercalcemia. Normal serum calcium levels are 8 to 10 mg per dL (2.0 to 2.5 mmol per L, Figure 1), although the exact range can vary among laboratories. Normal ionized calcium levels are 4 to 5.6 mg per dL (1 to 1.4 mmol per L). Hypercalcemia is considered mild if the total serum calcium level is between 10.5 and 12 mg per dL (2.63 and 3 mmol per L). Levels higher than 14 mg per dL (3.5 mmol per L) can be life threatening. PTH is an 84-amino acid hormone produced by the four pea-sized parathyroid glands posterior to the thyroid gland. In response to low serum calcium levels, PTH raises calcium H ypercalcemia is a disorder commonly encountered by primary care physicians. Approximately one in 500 patients who are treated in a general medicine clinic have undiagnosed primary hyperparathyroidism, the leading cause of hypercalcemia. The diagnosis of hypercalcemia most often is made incidentally when a high calcium level is detected in blood samples. The principal challenges in the management of hypercalcemia are distinguishing primary hyperparathyroidism from conditions that will not respond to parathyroidectomy and knowing when it is appropriate to refer the patient for surgery. It is essential that physicians know how to evaluate and optimally manage patients with hypercalcemia, because treatment and prognosis vary according to the underlying disorder.