Abstract
We investigated the effect of vitamin D withdrawal for 18 weeks on PTH secretion in hemodialysis patients with hypoparathyroidism. In patients with an intact (i) -PTH level below 10pg/ml and treated with vitamin D, i-PTH was increased from 6.4±0.3pg/ml to 50.9±11.6pg/ml after 18 weeks by withdrawing vitamin D. The serum calcium (Ca) level was significantly decreased after 2 weeks. There was a significant relationship between the change in i-PTH and serum Ca concentration. The serum phosphate (P) level tended to decrease after 2 weeks until 10 weeks. The serum magnesium (Mg) level was also significantly decreased from 3.64±0.18mg/dl to 3.15±0.14mg/dl, 3.10±0.13mg/dl after 10 and 18 weeks, respectively. There was no relationship between the changes in i-PTH and serum P and Mg levels. Therefore vitamin D might directly stimulate P and Mg absorption in the intestine. We conclude that a vitamin D supplement causes hypoparathyroidism via the increased serum Ca concentration in hemodialysis patients.
