Hypercalcemia clinical significance

Determination of PTH is useful in the differential diagnosis of both hypercalcemia and hypocalcemia for assessing parathyroid function in renal failure and for evaluating parathyroid function in bone and mineral disorders (see Calcium, Clinical Significance, Hypocalcemia, and Hypercalcemia Metabohc Bone Diseases and Interpretation of PTH Results). 

The maximum recommended dose for the treatment of hypercalcemia of malignancy is 4 mg. A clinically significant deterioration in renal function occurs when single doses of this agent exceed 4 mg and the infusion duration is less than 15 minutes (52). It is recommended that patients be well hydrated before infusion. If serum calcium levels do not fall to normal levels, retreatment is appropriate, but retreatment is not recommended until 7 days have elapsed from the initial treatment. For the treatment of multiple myeloma and metastatic bone lesions, a 4-mg initial dose is recommended, followed by additional doses every 3 to 4 weeks for 9 to 15 months (prostate cancer, 15 months breast cancer, 12 months other solid tumors, 9 months). 

Because the severity of symptoms and the absolute serum concentration are poorly correlated in some patients, institution of therapy should be dictated by the clinical scenario. All patients with hypercalcemia should be treated with aggressive rehydration normal saline at 200 to 300 mL/hour is a routine initial fluid prescription. For patients with mild hypocalcemia, hydration alone may provide adequate therapy. The moderate and severe forms of hypercalcemia are more likely to have significant manifestations and require prompt initiation of additional therapy. These patients may present with anorexia, confusion, and/or cardiac manifestations (bradycardia and arrhythmias with ECG changes). Total calcium concentrations greater than 13 mg/dL (3.25 mmol/L) are particularly worrisome, as these levels can unexpectedly precipitate acute renal failure, ventricular arrhythmias, and sudden death. 

Hypercalcemia Carefully monitor standard hypercalcemia-related metabolic parameters, such as serum levels of calcium, phosphate, and magnesium, as well as serum creatinine. Do not use loop diuretics until the patient is adequately rehydrated use with caution in combination with zoledronic acid in order to avoid hypocalcemia. Use zoledronic acid with caution with other nephrotoxic drugs. Concomitant use with estrogen/hormone replacement therapy (alendronate) Two clinical studies have shown that the degree of suppression of bone turnover (as assessed by mineralizing surface) was significantly greater with the combination than with either component alone. 

This rather common disease, if associated with symptoms and significant hypercalcemia, is best treated surgically. Oral phosphate and bisphosphonates have been tried but cannot be recommended. Asymptomatic patients with mild disease often do not get worse and may be left untreated. The calcimimetic agent cinacalcet, discussed previously, has been approved for secondary hyperparathyroidism and is in clinical trials for the treatment of primary hyperparathyroidism. If such drugs prove efficacious, medical management of this disease will need to be reconsidered. 

Diuretics have a wide range of clinical uses, including HTN, heart failure, edematous states, renal dysfunction, hypercalcemias, nephrolithiasis, glaucoma, and mountain sickness. Although they are classed as diuretics, recognize that both loops and thiazides cause significant vasodilation, an action that contributes to their clinical effectiveness, especially in HTN and heart failure. 

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