TREATMENT OF SEVERE SECONDARY HYPERPARATHYROIDISM WITH ADMINISTRATIONOF CALCIUM-CARBONATE, INTERMITTENT HIGH ORAL DOSES OF 1,25-DIHYDROXYVITAMIN-D(3) AND DIALYSATE WITH 3 MEQ L CALCIUM-CONCENTRATION/

In this study, we evaluated the effect of long-term administration of daily calcium carbonate (2-4 g/day) and intermittent high oral doses o f 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3, 3-4 mug, given twice a week] in conjunction with a 3-mEq/l calcium concentration in the dialysate for the treatment of severe secondary hyperparathyroidism in 6 hemodia lysis patients. All patients had reduced serum levels of 1,25-(OH)2D3, which increased significantly (p < 0.005) reaching the maximum level in the 4th month. Serum total and ionized calcium levels significantly increased also, in relation to those before treatment. No patients de veloped hypercalcemia. Serum phosphorus did not significantly change d uring the study. Initial serum intact parathyroid hormone (PTH) (1,241 +/- 233 pg/ml, mean +/- SEM) markedly decreased after starting treatm ent with 1,25-(OH)2D3, being 542 +/- 174 pg/ml in the 5th month and 47 7 +/- 174 pg/ml in the 8th month. These changes are statistically sign ificant (p < 0.05 and < 0.007, respectively). Alkaline phosphatase beh avior was similar to that of intact PTH. A constant direct correlation between intact PTH and alkaline phosphatase and an inverse significan t correlation between intact PTH and 1,25-(OH)2D3 was evidenced by us. We conclude that oral 1,25-(OH)2D3 pulse therapy is very effective in suppressing PTH secretion. The administration of calcium carbonate an d the use of dialysate with a reduced calcium concentration would allo w to prevent hyperphosphatemia and the administration of high oral dos es of 1,25-(OH)2D3 without concomitant hypercalcemia.