Lack of Effect of Thiazide Therapy on Serum 1,25-Dihydroxyvitamin D in Idiopathic Hypercalciuria with Renal Calculi

Abstract

Thiazide diuretics cause a persistent lowering effect on urinary Ca excretion in normal subjects and in patients with idiopathic hypercalciuria. By reabsorbing ultrafilterable Ca, this drug is considered to have a selective effect in suppressing parathyroid activity, particularly in renal hypercalciuric patients. In association with this, a reduction in serum 1, 25-dihydroxyvitamin D is also found and a decrease in intestinal Ca absorption (1). However, thiazides are reported to have no action on parathyroid hormone - vitamin D feedback in absorptive hypercalciuria because of the believed parathyroid-hormone-independent vitamin D₃ increased production rate (1). Moreover, such diuretics have also been shown to reduce the turnover of body Ca (2) which is reported to be significantly increased in unselected people with idiopathic hypercalciuria and kidney stone disease (3). The aim of this study was to assess body Ca turnover and vitamin D serum levels in each of the hypercalciuric subgroups of patients, and to look for modifications in the post-thiazide treatment period.