Renal handling of calcium in hypoparathyroidism.

Treatment of hypoparathyroidism usually requires the use of pharmacological doses of parent vitamin D or near physiological amounts of the hydroxylated metabolites, calcitriol or alphacalcidol. Vitamin D intoxication and hypercalcaemia may be a problem but can be minimised by the use of small doses of vitamin D or its metabolites combined with large amounts of oral calcium. The response to treatment can be easily monitored by measuring serum and urinary calcium and creatinine concentrations. This allows the derivation of two simple indices reflecting calcium load presented to the kidney (calcium excretion in mmol/l glomerular filtrate) and renal tubular calcium reabsorption (TmCa/GFR). These can be used to predict the requirement of calcium supplements and also identify those patients at particular risk of hypercalcaemia.