RESUMO
Calcitonin-secreting cells, 'C cells', have specific receptors for calcitriol, thus the calcitriol deficiency in uraemia may affect calcitonin secretion and/or production. The aim of the present study was to evaluate in CAPD patients the effect of calcitriol replacement (4 weeks of oral calcitriol, 0.5 micrograms/day) on both, basal calcitonin concentration and calcitonin response to calcium infusion (calcium gluconate, 3 mg/kg/h). Calcitriol replacement produced a normalization of serum calcitriol level without a significant change in serum calcium concentration. After calcitriol replacement, basal calcitonin increased from 78 +/- 15 to 101 +/- 13 pg/ml, P < 0.05. The increment in calcitonin induced by a calcium infusion was lower after (15 +/- 4 pg/ml) than before (29 +/- 4 pg/ml) calcitriol replacement. In addition, calcitriol administration induced a decrease in serum PTH level. Replacement of calcitriol in CAPD patients produced an increase in serum calcitonin concentration and a decrease in the calcitonin response to hypercalcaemia.