Thiazide diuretics in renal hypercalciuria.

Forty-six renal hypercalciuric normocalcaemic patients were treated with hydrochlorothiazide (50mg/day) and amiloride (5 mg/day), both to reduce new stone formation and to suppress parathyroid hyperfunction. A reduction of hypercalciuria and suppression of parathyroid hyperactivity were observed in 41 patients, while in the other five patients no evidence of parathyroid suppression was found and hypercalcaemia developed. Four of five patients underwent parathyroidectomy which was followed by a normalisation of biochemical signs of hyperparathyroidism. These results suggest that the appearance of hypercalcaemia in renal hypercalciuric patients during hydrochlorothiazide/amiloride treatment may be of diagnostic value in unmasking pharmacologically non-suppressible normocalcaemic hyperparathyroidism.