Response of different PTH assays to therapy with sevelamer or CaC[O.sub.3] and active vitamin D sterols

• Published in: Pediatric nephrology (Berlin, West) Vol. 24; no. 7; p. 1355
• Main Authors: Wang, He-Jing, Gales, Barbara, Wesseling-Perry, Katherine, Sahney, Shobha, Salusky, Isidro B, Harkins, G. Chris, Juppner, Harald, Elashoff, Robert M
• Format: Journal Article
• Language: English
• Published: Springer 01.07.2009
• ISSN: 0931-041X

Amino-terminally truncated parathyroid hormone (PTH) fragments are detected to differing degrees by first-and second-generation immunometric PTH assays (PTHIMAs), and acute changes in serum calcium affect the proportion of these fragments in circulation. However, the effect of chronic calcium changes and different vitamin D doses on these PTH measurements remains to be defined. In this study, 60 pediatric dialysis patients, aged 13.9 ± 0.7 years, with secondary hyperparathyroidism were randomized to 8 months of therapy with oral vitamin D combined with either calcium carbonate (CaC[O.sub.3]) or sevelamer. Serum phosphorus levels did not differ between groups. Serum calcium levels rose from 9.3 ± 0.1 to 9.7 ± 0.1 mg/dl during CaC[O.sub.3] therapy (p<0.01 from baseline) but remained unchanged during sevelamer therapy. In the CaC[O.sub.3] and sevelamer groups, baseline serum PTH levels (1st PTH-IMA; Nichols Institute Diagnostics, San Clemente, CA) were 964 ± 75 and 932 ± 89 pg/ml, and levels declined to 491 ± 55 and 543 ± 59 pg/ml, respectively (nonsignificant between groups). Patients treated with sevelamer received higher doses of vitamin D than those treated with CaC[O.sub.3]. The PTH values obtained by first- and second-generation PTH-IMAs correlated closely throughout therapy and the response of PTH was similar to both PTH-IMAs, despite differences in serum calcium levels. Keywords Calcium carbonate * Parathyroid hormone * Secondary hyperparathyroidism * Sevelamer * Vitamin D