Response of different PTH assays to therapy with sevelamer or CaCO3 and active vitamin D sterols.
Amino-terminally truncated parathyroid hormone (PTH) fragments are detected to differing degrees by first- and second-generation immunometric PTH assays (PTH-IMAs), 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 (CaCO(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 CaCO(3) therapy (p < 0.01 from baseline) but remained unchanged during sevelamer therapy. In the CaCO(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 CaCO(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.
Wesseling-Perry
Katherine
K
Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA. kwesseling@mednet.ucla.edu
Harkins
G Chris
GC
Wang
He-Jing
HJ
Sahney
Shobha
S
Gales
Barbara
B
Elashoff
Robert M
RM
Jüppner
Harald
H
Salusky
Isidro B
IB
D000293:Adolescent; D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D002118:Calcium / Q000097:blood; D002119:Calcium Carbonate / Q000008:administration & dosage*; D002614:Chelating Agents / Q000008:administration & dosage*; D002648:Child; D002675:Child, Preschool; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood / Q000188:drug therapy; D007118:Immunoassay / Q000379:methods*; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood*; D010758:Phosphorus / Q000097:blood; D011073:Polyamines / Q000008:administration & dosage*; D006435:Renal Dialysis; D000069603:Sevelamer; D014807:Vitamin D / Q000008:administration & dosage*
D002614:Chelating Agents; D010281:Parathyroid Hormone; D011073:Polyamines; D014807:Vitamin D; D010758:Phosphorus; D000069603:Sevelamer; D000469:Alkaline Phosphatase; D002119:Calcium Carbonate; D002118:Calcium