title: Secretion of parathyroid hormone oscillates depending on the change in serum ionized calcium during hemodialysis and may affect bone metabolism.
abstract: BACKGROUND
  The current study was undertaken to clarify the dynamic response of parathyroid hormone (PTH) during hemodialysis and to determine whether or not such dynamic change of PTH affects bone turnover.
  
  
  METHODS
  Serum ionized calcium (iCa) and intact PTH (iPTH) were measured in 66 dialysis patients before (basal) and after each hemodialysis. The changes of iCa (DeltaiCa) and iPTH (DeltaiPTH) were defined as [postdialysis iCa -basal iCa] mM, and [(postdialysis iPTH - basal iPTH)/basal iPTH] x 100%, respectively. We also investigated the data of the patients divided into four groups based on their basal iPTH levels; group 1 (iPTH < 60 pg/ml, n = 17), 2 (> or = 60 to < 150, n = 20), 3 (> or = 150 to < 300, n = 15), and 4 (> or = 300, n = 14).
  
  
  RESULTS
  While iCa and iPTH changed variably during each hemodialysis procedure, there was a highly significant inverse correlation between DeltaiCa and DeltaiPTH (r = -0.761, p < 0.0001). Regression coefficients between DeltaiPTH and DeltaiCa were -519.1, -311.2, -268.1, and -194.6%/mM in groups 1-4, respectively. The difference in the regression coefficient was statistically significant between group 1 and 2 (F = 3.69, p < 0.05, ANCOVA), group 1 and 3 (F = 5.599, p < 0.05), and group 1 and 4 (F = 10.853, p < 0.005). This suggested that patients with higher basal iPTH responded poorly to modulate serum PTH levels by sensing the change of iCa. However, after an intensified oral calcitriol therapy to reduce iPTH, the PTH response in group 4 patients was restored to levels comparable with those observed in patients having lower basal iPTH. We also demonstrate that the DeltaiPTH of patients of group 1 but not of other groups was significantly correlated with serum markers for bone metabolism; osteocalcin (r = 0.535, p < 0.05) and collagen type I C-terminal telopeptide (r = -0.575, p < 0.05).
  
  
  CONCLUSIONS
  Our findings suggest that secretion of PTH is dynamically regulated by DeltaiCa during hemodialysis and such oscillated PTH secretion may affect bone metabolism in a subset of dialysis patients.
authors.affiliation: Department of Medicine and Clinical Science, Gunma University Graduate School of Medicine, Maebashi, Japan. tkita1@jcom.home.ne.jp
authors.forename: Tokuyuki
authors.initials: T
authors.lastname: Kitahara
authors.forename: Kazue
authors.initials: K
authors.lastname: Ueki
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuroiwa
authors.forename: Yoriaki
authors.initials: Y
authors.lastname: Kaneko
authors.forename: Keiju
authors.initials: K
authors.lastname: Hiromura
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nojima
mesh_terms: D000328:Adult; D000368:Aged; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D003094:Collagen / Q000097:blood; D024042:Collagen Type I; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood* / Q000378:metabolism; D010455:Peptides / Q000097:blood; D006435:Renal Dialysis
chemical_list: D024042:Collagen Type I; D010281:Parathyroid Hormone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D003094:Collagen; D002118:Calcium