Therapeutic strategy of relative hypoparathyroidism in hemodialysis patients using sevelamer hydrochloride, with special reference to vitamin D administration - The effect of sevelamer hydrochloride on relative hypoparathyroidism in hemodialysis patients

Sevelamer hydrochloride has been expected to control hyperphosphatemia without calcium load. In this study, we investigated the effects of attenuation of calcium load by sevelamer hydrochloride on bone metabolic markers in 46 hemodialysis patients with serum intact parathyroid hormone (iPTH) levels < 150 pg/mL. After replacement of calcium carbonate with sevelamer, their serum calcium levels decreased. The iPTH levels increased after 4 weeks and the magnitude of the increase was significantly correlated with the extent of decrease in serum calcium concentration. The whole PTH, bone alkaline phosphatase (BAP), and bone-specific tartrate-resistant acid phosphatase (TRAP5b) levels were also increased after 12 weeks. However, the relationship between iPTH and BAP or TRAP5b which was observed before the sevelamer replacement therapy was preserved only in the patients with serum iPTH levels < 60 pg/mL at enrollment. Thus, in the patients with pretreatment iPTH levels >= 60 and < 150 pg/mL, the increase in iPTH level might not always result in the improvement of bone metabolism. In the patients administered with vitamin D at enrollment, the frequency of overshooting of iPTH, BAP, or TRAP5b was lower than that in the patients without vitamin D administration. In conclusion, replacing calcium carbonate with sevelamer could be a therapeutic option in the patients with hypoparathyroidism (iPTH < 60 pg/mL) to improve bone metabolism and vitamin D might be useful to avoid the excess enhancement of bone turnover by sevelamer therapy.