[Hypercalcemia].

Severe hypercalcemia is mainly caused by inappropriately high concentrations of compounds which promote bone resorption, in particular PTH, PTHrP, or 1,25 (OH)2D3. The major consequences are impaired central nervous system and kidney function (polyuria/dehydration); the latter, in turn, aggravate hypercalcemia via decreased fluid intake, mobility, and renal calcium clearance. The most common causes of hypercalcemia are primary hyperparathyroidism and tumors, drugs (in particular thiazides, lithium, vitamin D and vitamin A and their derivatives), granulomatous and infectious diseases. The patient with mild hypercalcemia should be controlled (and if necessary operated on for adenoma of the parathyroid glands), while the patient with acute severe hypercalcemia needs to be treated immediately by (1.) 0.9% NaCl i.v. to restore plasma volume, (2.) bisphophonates i.v. to block bone resorption, and (3.) therapy for the underlying disorder.