RESUMO
In this study, we evaluated the effect of long-term administration of daily calcium carbonate (2-4 g/day) and intermittent high oral doses of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3, 3-4 micrograms, given twice a week] in conjunction with a 3-mEq/1 calcium concentration in the dialysate for the treatment of severe secondary hyperparathyroidism in 6 hemodialysis 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 developed hypercalcemia. Serum phosphorus did not significantly change during the study. Initial serum intact parathyroid hormone (PTH) (1,241 +/- 233 pg/ml, mean +/- SEM) markedly decreased after starting treatment with 1,25-(OH)2D3, being 542 +/- 174 pg/ml in the 5th month and 477 +/- 174 pg/ml in the 8th month. These changes are statistically significant (p < 0.05 and < 0.007, respectively). Alkaline phosphatase behavior was similar to that of intact PTH. A constant direct correlation between intact PTH and alkaline phosphatase and an inverse significant 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 and the use of dialysate with a reduced calcium concentration would allow to prevent hyperphosphatemia and the administration of high oral doses of 1,25-(OH)2D3 without concomitant hypercalcemia.
