Effect of hydrochlorothiazide on 1,25-dihydroxyvitamin D3-induced changes in calcium metabolism in experimental hypoparathyroidism in rats

Management of disorders of calcium homoeostasis

Severe hypercalcaemia may be life-threatening and requires prompt management. Whatever the cause, the aim of therapy should obviously be to eradicate the source of hypercalcaemic factors. After rehydration, which is an essential first step in the management strategy, and after evaluation of the prevailing pathogenetic mechanism, the acute treatment will be aimed at increasing urinary Ca excretion and inhibiting bone resorption. Among the various pharmacological agents, bisphosphonates appear to be the drugs of first choice, because of their efficacy and their virtual absence of side-effects. The decision to treat hypocalcaemia is determined by the extent of the symptoms and the risk of complications. The treatment of acute hypocalcaemia comprises the parenteral administration of Ca or magnesium, when magnesium deficiency can be suspected. Then, chronic hypocalcaemia may require the use of 1,25-dihydroxyvitamin D, once the replenishments of vitamin D stores have been assured.

Diuretics and calcium metabolism

In this review the normal renal tubular handling of calcium is briefly described. A detailed examination follows of the sites and modes of action of furosemide and thiazide diuretics on renal calcium handling and overall calcium metabolism. The clinical applications of these effects are also considered. Finally, the use of diuretics with different tubular sites of action on calcium transport as probes to study disorders of calcium excretion is discussed.