Addison's disease presenting as a hypercalcemic crisis in a patient with idiopathic hypoparathyroidism.

A patient with idiopathic hypoparathyroidism complicated by Addison's disease is described. The development of adrenal insufficiency was accompanied by a hypercalcaemic crisis. The hypercalcaemia appeared to result from a reduction in the filtered load and enhanced renal tubular reabsorption of calcium. Cortisone therapy was followed by the characteristic renal tubular leak of calcium associated with hypoparathyroidism and a return of the serum calcium to normal. The possible mechanisms for these changes in calcium homeostasis are discussed.